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[MUSIC PLAYING]

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DAVID J. MALAN: All right, this is CS50.

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And this is not a typical week of CS50.

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Indeed, we're midweek
here in the fall of 2020

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here on campus, which would
normally be first year family

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weekend, an opportunity for
the parents and family members

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of the undergraduates here at
Harvard to actually come to campus,

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sit in on classes, attend talks, and
get to know their students in situ

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here right on campus.

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Of course, this
particular year, all of us

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are staying afar, digitally,
except those of us

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who are actually here living
in Cambridge itself already.

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And so what we thought we would do this
year is hold a virtual talk of sorts,

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a virtual discussion focused on
one topic that doesn't require

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any prior familiarity
with computer science,

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does not require that
you be in or have taken

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CS50 itself because it's about
a topic that's at least in part

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familiar to all of us.

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Even if it's a little bit
less familiar technically,

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it's certainly familiar to all
of us as users of technology.

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And that topic is
security or cybersecurity.

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And what we propose
today is that we have

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a discussion about how you might go
about keeping your own computer-- be

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it a laptop or desktop
or your own phone, which

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is also a form of computer-- secure.

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And I daresay that this
topic, even though we'll

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get into some of the technicalities
of what it means to be secure,

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is familiar in the sense that all of us
think about or encounter good security

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and bad security in the
real world every day.

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Think about the home that you live
in, be it a house or an apartment

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or a dormitory or somewhere else.

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Typically, you'll have things,
like, locks on the doors.

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And you might even,
depending on where you live,

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have bars on the windows and the like.

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But typically, there are manifestations
of security at different levels.

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And I mean that literally.

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For instance, in a typical
city, there might be bars

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on the first floor windows, but not on
the second floor or the third floor.

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And that is to say that
someone could technically

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make their way into your home by way
of the second floor or the third floor,

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but it's going to be more difficult,
of course, because they need a ladder.

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They need some other
form of physical access

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to a height like that, at
which point, they're probably

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going to attract more attention.

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And so the probability
that an adversary is

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going to break into your
home given that they

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have to actually rise to that
level and get above the first floor

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is probably relatively low.

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It's not zero.

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There's nothing stopping someone
technically from pulling up a ladder

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and going into that open window
or the light that has no bars.

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But it's less likely.

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And that's actually a good way to think
about security in the digital world

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as well, that there's really
no such thing as secure.

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Like, your phone is not
secure fundamentally.

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Your laptop, your desktop
is not secure fundamentally.

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It's secure to some extent.

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It might be secure against certain
attacks or certain types of adversaries

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or adversaries with certain
amounts of resources.

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And those resources might be time, might
be money, might be technical savvy.

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But it really is going
to be a trade-off.

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And so while a bit unfortunate,
one way of thinking about security

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is that you don't want to be
a secure in an absolute sense.

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In the real world, you want to be more
secure than your neighbor's house,

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for instance.

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You want to somehow raise the bar,
either physically or metaphorically,

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to the adversary so that it's going
to take that adversary just too

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much time, too much money too much
effort to break into your home

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that they might as well
just go next door instead.

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And the same is going to be
true in the world of computers.

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But we're going to measure
the security of systems

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more computationally,
not so much physically.

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So with that said, let me invite you to
open up this URL here on your screen.

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If you're using a laptop or desktop,
go ahead and just open it up

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in a separate tab in another browser.

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If you're on your phone,
you can go back and forth

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between two windows most likely,
depending on your operating system.

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But go ahead, when you have a
moment, and open up this URL.

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And we'll use this URL to ask
a few interactive questions

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that you can respond to digitally.

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And we'll also take questions and
comments throughout today as well.

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So with that said, what does
it mean to be secure, then?

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Let's take a couple of thoughts on this.

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What do you think of the
word "secure" as meaning

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in the context of your phone,
of your computer, of your home?

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Interpret as you will.

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What does it mean to be
secure, would you say?

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Any digital hands in Zoom?

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If you're feeling shy,
feel free to chime

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in via the chat and Brian can proxy.

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But otherwise, do feel free
to raise your hand virtually

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if you would like to
offer your definition.

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Yeah, how about over to Pranav,
if I'm pronouncing it right?

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What does it mean to be secure?

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PRANAV: Yeah, I think
it means, by security,

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you mean to protect all the data
that's stored on a particular system

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if we're talking about technology.

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And at least make it hard
and buy yourself enough time

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that a certain person may not hack
into your system at the current moment

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because--

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DAVID J. MALAN: Good.

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PRANAV: --let's face it.

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You may not be able to protect your
system for your entire lifetime.

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But I would say, at least buy yourself,
continuously buy yourself time.

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DAVID J. MALAN: OK, I like that.

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So security is all about keeping
someone out of your resources.

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But as I myself have claimed thus far,
that's hard to argue in the absolute.

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Really you want your system to just take
too much time to compromise, your phone

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or your laptop to take too much
time to compromise, at which point

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you're sort of probabilistically,
statistically safe against adversaries.

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Because again, they're not going to
want to waste that much time or effort

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or money hacking into your particular
system versus someone else.

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Now, there are different ways
that you and I in the real world

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try to keep our laptops
and our phones secure.

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And one of those most popular
mechanisms is, of course, passwords.

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Passwords, being some kind of phrase,
some kind of number that you actually

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configure your device with so that
ideally, only you know that password.

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And only you, therefore, can get into
the device by using that password.

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And so by a show of physical
hands, how many of you

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have passwords on your
laptops or desktops

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if you use one of those devices?

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So almost all of the hands are going up.

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Those of you who don't have your
hand going up, you've probably made,

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I presume, a conscious
choice to not use a password.

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Maybe it's annoying to type in.

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Maybe you don't really
worry about anyone

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around you getting into the device.

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But you should concede or recognize
that there is therefore a threat.

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It's much easier for someone to
get into your laptop or desktop

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then into that of anyone else who
raised their hand just a moment ago.

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Now, those of you who have a
phone, a mobile device, those

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of you with that device,
how many of you have

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a password or a passcode on
that device, on your phone?

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So somewhat fewer hands I'm seeing.

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So it's good that so
many hands are going up.

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But there, too, it seems
that some of you don't have.

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And hopefully, you've thought
about the implications

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of that, which means that your parents,
your siblings, a stranger, if they just

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physically pick up your phone,
whether it's in your home

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or in a cafe or an airport, has
immediate access to all of your data.

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So arguably, much less
secure, certainly,

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than someone that requires a password.

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But let's consider how we can
measure the security of your phone,

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measure the security
of your computer, just

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by using this simple familiar
mechanism, like, a password.

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So it turns out that you
and I, frankly, as humans,

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aren't very good at picking these
passwords in the first place.

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As of 2019, just some
months ago at year's end,

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this was determined by security
researchers to be sadly,

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the most common password in
the world, literally, 123456.

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That was the most common
password according

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to many measures this past year among
those passwords that were known.

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Number two on the list was
slightly better, 123456789.

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After that was qwerty.

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If that one looks a little weird, if you
have a US English keyboard and you look

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at the top left row of your keys,
Q-W-E-R-T-Y is what they would spell

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on a US keyboard.

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People are really not trying very
hard to come up with their password,

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even though it's not technically
an English word, per se.

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Password was the number four most
popular password, P-A-S-S-W-O-R-D,

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which is a little too tongue
in cheek to be at all secure.

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After that was slightly worse, 1234567;
after that, 12345678; after that,

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12345.

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You can perhaps see the pattern here.

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After that was, adorably, iloveyou.

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But if you think you're being clever
by having iloveyou as your password,

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well, there's a lot of other
humans in the world that

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think they're being cute, too.

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111111 was also popular.

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And then lastly, 123123.

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So now why these passwords?

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You can perhaps infer from this
list why some of these passwords

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are the way that they are.

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Odds are these people were using these
passwords on phones or on websites

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or in other systems that probably
had, like, a minimum password length.

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These people probably needed a
password that was six characters long.

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These people probably needed one that
was nine characters long, and so forth.

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So you can perhaps see some
manifestations of policies

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that companies and universities
and software manufacturers

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might have in place.

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But suffice it to say, if
your password is on this list,

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your first takeaway
from today's discussion

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should be change that password--

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at least if you care about the account.

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And I would argue, too, and
we'll come back to this,

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it really probably should
figure into your decision making

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what type of account it is.

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If it's for some silly website or game
that you're never going to use again,

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maybe it's not a big deal.

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If it's your bank account, your student
record, something medical related,

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probably you really don't want
your password on this list.

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So there, too, consider the context in
which we make all of today's decisions.

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Now, why are these passwords bad?

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And why are passwords
themselves potentially at risk?

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So a term of art in computer science
is that of brute force attacks.

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And this kind of is what it says.

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This refers to an adversary-- someone
who's out to get you or get someone--

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has a device or writes software that
tries to just guess your password.

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Brute force attack means that if
they don't know your password,

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they're not just going to try
random numbers necessarily.

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They're going to try 111111.

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And then they're going to try 111112.

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Then they're going to try 111113, either
manually, by typing it into the phone

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that they might have stolen off of
you, or maybe by writing software,

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and then connecting that
software via a laptop

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or desktop to your phone via USB cable
or lightning connector or the like.

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A brute force attack
pretty much just means

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that the adversary doesn't necessarily
know anything about you-- your name,

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your birthday, your children's
names, nothing like that.

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But they do have a lot of
time or a lot of skill.

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And so they're just going to
try all possible passwords.

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And what's eye opening, I
think, about this type of attack

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is that it already
gives us an opportunity

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to start thinking about how can we
protect ourselves against an attack?

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And just right now, how secure are your
accounts on your phones and computers

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against brute force attacks?

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Well, let's consider how
an adversary might do this.

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This is kind of a silly
YouTube video here.

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But let me go ahead and
play this animation, really,

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which shows a small robot of sorts that
is typing using this little robotic arm

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onto an Android phone down there.

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There's a zoomed in version of it.

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And pretty much this
is a brute force attack

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by a robot, a physical device
that an adversary has designed

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to just type in all possible passcodes.

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And even though the
video itself is short,

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you can imagine the adversary going
about their day, going to sleep.

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And this thing just keeps brute
forcing its way through your password.

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So eventually, it might get lucky
and stumble upon whatever code you

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were indeed using.

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But of course, there's
probably other threats, too.

232
00:12:30,803 --> 00:12:31,720
There's other threats.

233
00:12:31,720 --> 00:12:34,900
In fact, anyone who's
taken CS50 or CS50x or even

234
00:12:34,900 --> 00:12:38,920
just the first few weeks of it,
learning a little bit of C or Python,

235
00:12:38,920 --> 00:12:41,770
both of which are common
programming languages, anyone

236
00:12:41,770 --> 00:12:44,020
who knows a little bit about
programming can certainly

237
00:12:44,020 --> 00:12:48,160
write software that simulates what
that robot was physically doing.

238
00:12:48,160 --> 00:12:51,790
And the thing about software is as soon
as you don't have any moving parts,

239
00:12:51,790 --> 00:12:54,940
you can do things much, much
faster because it's all electronic.

240
00:12:54,940 --> 00:12:56,630
It's not at all mechanical.

241
00:12:56,630 --> 00:13:00,520
And so in this case, what if
I were to steal your phone off

242
00:13:00,520 --> 00:13:04,060
of you, for instance, write
some software on my Mac or PC,

243
00:13:04,060 --> 00:13:06,730
and then plug my Mac
or PC into your phone

244
00:13:06,730 --> 00:13:09,580
with, again, a USB cable
or a lightning connector,

245
00:13:09,580 --> 00:13:14,050
such that I could write code that tries
all possible passcodes again and again?

246
00:13:14,050 --> 00:13:16,810
For instance, suppose
that your phone is using--

247
00:13:16,810 --> 00:13:21,790
and this is not an uncommon default
on iPhones or on Android phones,

248
00:13:21,790 --> 00:13:23,020
at least in the past--

249
00:13:23,020 --> 00:13:24,070
four digits.

250
00:13:24,070 --> 00:13:26,170
Suppose that you're
required to choose minimally

251
00:13:26,170 --> 00:13:30,520
a passcode or password, synonymous
here, that are four digits long.

252
00:13:30,520 --> 00:13:33,010
And we're talking decimal
digits, so 0 through 9.

253
00:13:33,010 --> 00:13:35,350
So 0, 1, 2, 3, 4, 5,
6, 7, 8, 9, you need

254
00:13:35,350 --> 00:13:38,170
to choose four of those
digits in some pattern.

255
00:13:38,170 --> 00:13:44,230
Well, how many possible passcodes
are there that are four digits long?

256
00:13:44,230 --> 00:13:48,700
If your passcode is 4 digits long, you
can begin to think about the security

257
00:13:48,700 --> 00:13:52,900
of your passcode in terms of, well,
how long would it take an adversary

258
00:13:52,900 --> 00:13:58,210
to brute force their way to my
actual password starting at 0000,

259
00:13:58,210 --> 00:14:01,135
going all the way up
to, for instance, 9999.

260
00:14:01,135 --> 00:14:03,010
Well, let me go ahead
and open up the screen.

261
00:14:03,010 --> 00:14:07,330
If you pull up that same URL from
before, you'll see in just a moment

262
00:14:07,330 --> 00:14:12,070
a poll that'll ask you this
very same question, that being,

263
00:14:12,070 --> 00:14:15,338
how many 4-digit passcodes are possible?

264
00:14:15,338 --> 00:14:17,380
In just a moment, you'll
see this on your screen.

265
00:14:17,380 --> 00:14:19,750
Let me go ahead and full
screen it on my end as well.

266
00:14:19,750 --> 00:14:22,600
Go again to the URL that's
atop my screen here,

267
00:14:22,600 --> 00:14:26,770
if you missed the URL earlier
or happened to close the tab.

268
00:14:26,770 --> 00:14:31,180
How many 4-digit passcodes are possible?

269
00:14:31,180 --> 00:14:33,910
How many 4-digit passcodes are possible?

270
00:14:33,910 --> 00:14:40,180
Among the answers here are 4 or
40 or 9,999 or maybe 10,000--

271
00:14:40,180 --> 00:14:42,940
or quite fine, too, you're unsure.

272
00:14:42,940 --> 00:14:50,170
Go ahead and buzz in with one of
those responses, if you could.

273
00:14:50,170 --> 00:14:53,140
All right, looks like we have got
a few hundred responses thus far.

274
00:14:53,140 --> 00:14:56,520
We'll give you a few
more seconds to buzz in.

275
00:14:56,520 --> 00:14:59,160
And let me go ahead and begin
to reveal the results here.

276
00:14:59,160 --> 00:15:03,645
So it looks like quite
a few of you, 60-plus%

277
00:15:03,645 --> 00:15:05,520
think it's 10,000 possibilities.

278
00:15:05,520 --> 00:15:08,730
27% of you think it's
9,999 possibilities.

279
00:15:08,730 --> 00:15:10,590
And then a few others
think it's 40 or four.

280
00:15:10,590 --> 00:15:12,210
And a bunch of you are unsure.

281
00:15:12,210 --> 00:15:14,130
So let's consider, then,
how we would answer

282
00:15:14,130 --> 00:15:17,670
this question so that we have a mental
model for answering this on our own.

283
00:15:17,670 --> 00:15:20,950
Let me go ahead and propose
that to answer this question,

284
00:15:20,950 --> 00:15:22,770
we just do some very simple arithmetic.

285
00:15:22,770 --> 00:15:24,600
It doesn't need to get very complicated.

286
00:15:24,600 --> 00:15:28,090
But the math could be thought
of in the following way.

287
00:15:28,090 --> 00:15:31,980
If we've got a 4-digit passcode,
that's four digits, each of which

288
00:15:31,980 --> 00:15:33,420
can be zero through nine.

289
00:15:33,420 --> 00:15:34,770
And there's 10 total digits.

290
00:15:34,770 --> 00:15:37,680
Therefore zero through 9.

291
00:15:37,680 --> 00:15:42,490
Eight nine so 10 possible values
for each of those four digits.

292
00:15:42,490 --> 00:15:44,790
So if that's the case,
I think it's fair to say

293
00:15:44,790 --> 00:15:48,480
that there's 10 possibilities for the
first digit times 10 possibilities

294
00:15:48,480 --> 00:15:51,507
for the second times 10 times 10.

295
00:15:51,507 --> 00:15:53,340
And of course, if you
multiply this all out,

296
00:15:53,340 --> 00:15:56,680
the answer was indeed
10,000 possibilities.

297
00:15:56,680 --> 00:15:59,370
So if you have an iPhone or
an Android phone right now

298
00:15:59,370 --> 00:16:03,060
and you've got a 4-digit passcode
that you think no one knows,

299
00:16:03,060 --> 00:16:04,800
that may very well be the case.

300
00:16:04,800 --> 00:16:07,200
But you should worry
about or consider, well,

301
00:16:07,200 --> 00:16:10,740
what happens if a friend with a fancy
robot connects your phone to that

302
00:16:10,740 --> 00:16:18,180
and just tries all possible values
from 0000 to 9999, or smarter still,

303
00:16:18,180 --> 00:16:21,120
connects your phone via
cable to their laptop,

304
00:16:21,120 --> 00:16:24,690
writes software to generate
all of those possibilities?

305
00:16:24,690 --> 00:16:28,740
Well, a little worrisomely, it's
not all that hard to do the latter

306
00:16:28,740 --> 00:16:30,210
and to actually write code.

307
00:16:30,210 --> 00:16:33,450
So in fact, let me go ahead here
and on my own Mac, let me go ahead

308
00:16:33,450 --> 00:16:36,540
and open up a program
that's going to let me write

309
00:16:36,540 --> 00:16:39,150
some code in a file called crack.py.

310
00:16:39,150 --> 00:16:41,230
So "crack" is a term
of art in programming,

311
00:16:41,230 --> 00:16:44,790
which means to brute force your
way into a password somehow,

312
00:16:44,790 --> 00:16:47,507
so to figure out what
it is algorithmically.

313
00:16:47,507 --> 00:16:50,340
Those of you, particularly parents
and family members who have never

314
00:16:50,340 --> 00:16:52,170
seen any of this before, totally fine.

315
00:16:52,170 --> 00:16:53,580
That's new to you.

316
00:16:53,580 --> 00:16:56,760
Your sons and daughters
and others here in the room

317
00:16:56,760 --> 00:16:58,440
have seen little bit of this code.

318
00:16:58,440 --> 00:17:01,080
But we'll keep it short, which
is to say that it actually

319
00:17:01,080 --> 00:17:04,680
doesn't take all that much
effort to write code that brute

320
00:17:04,680 --> 00:17:06,496
forces an attack on your own phone.

321
00:17:06,496 --> 00:17:09,329
And the code I'm going to write
here is in a language called Python,

322
00:17:09,329 --> 00:17:11,079
which is quite popular these days.

323
00:17:11,079 --> 00:17:15,450
And I'm going to say a command like
this, from string import digits, which

324
00:17:15,450 --> 00:17:18,520
is just a clever way in Python,
this programming language,

325
00:17:18,520 --> 00:17:22,290
just give me access to all the possible
digits in decimal, 0 through 9.

326
00:17:22,290 --> 00:17:26,430
And then I'm going to import, so to
speak, from a library, some software

327
00:17:26,430 --> 00:17:29,940
that some other smart people
wrote, something called product.

328
00:17:29,940 --> 00:17:32,010
So it turns out, in a
programming language,

329
00:17:32,010 --> 00:17:34,650
you have lots of functions
or functionality.

330
00:17:34,650 --> 00:17:38,110
Much like in the world of math, you have
functions, like, addition, subtraction,

331
00:17:38,110 --> 00:17:39,330
multiplication, and division.

332
00:17:39,330 --> 00:17:42,510
In the world of programming, you
have all of those capabilities,

333
00:17:42,510 --> 00:17:43,500
but many more.

334
00:17:43,500 --> 00:17:45,900
And so one of the functions
I'm importing here

335
00:17:45,900 --> 00:17:48,090
is this notion of a product,
which really just means

336
00:17:48,090 --> 00:17:52,178
a permutation of all possible digits.

337
00:17:52,178 --> 00:17:54,720
And now I'm going to use what's
called a loop in programming.

338
00:17:54,720 --> 00:17:57,803
A loop in a program is just something
that does something again and again.

339
00:17:57,803 --> 00:18:00,270
And I'm going to go ahead
and say this, for passcode

340
00:18:00,270 --> 00:18:06,660
in, the product of all of those digits,
and repeat the digits four times total,

341
00:18:06,660 --> 00:18:09,810
go ahead and print out each passcode.

342
00:18:09,810 --> 00:18:13,440
Let me go ahead and print it out
using somewhat cryptic syntax.

343
00:18:13,440 --> 00:18:17,310
But that's only because I'm going to
print out a list as an actual string.

344
00:18:17,310 --> 00:18:20,140
Parents and family members, don't
worry for now what that means.

345
00:18:20,140 --> 00:18:23,370
CS50 and CS50x students,
this is just a clever way

346
00:18:23,370 --> 00:18:26,010
with a couple of lines
of code to iterate over

347
00:18:26,010 --> 00:18:30,390
all of the digits 0 through 9,
combine them four at a time,

348
00:18:30,390 --> 00:18:35,200
and print out all possible
permutations of those four digits.

349
00:18:35,200 --> 00:18:38,430
So if I didn't screw up here, I'm going
to go ahead and save my file and run

350
00:18:38,430 --> 00:18:42,780
a command called python on
crack.py and hit Enter--

351
00:18:42,780 --> 00:18:43,785
boom.

352
00:18:43,785 --> 00:18:45,090
That was so fast.

353
00:18:45,090 --> 00:18:46,410
In fact, let me do it again.

354
00:18:46,410 --> 00:18:49,590
Let me clear my screen and
rerun this crack.py program--

355
00:18:49,590 --> 00:18:50,610
boom.

356
00:18:50,610 --> 00:18:53,790
That's how fast a computer,
my little Mac here,

357
00:18:53,790 --> 00:18:59,040
can try all possible codes
between 0000 and 9999.

358
00:18:59,040 --> 00:19:01,920
And it's so fast because it did
them all in the blink of an eye.

359
00:19:01,920 --> 00:19:04,920
So if you're thinking that your 4-digit
passcode is keeping you somewhat

360
00:19:04,920 --> 00:19:09,630
secure, it probably really isn't because
it wouldn't take that much effort

361
00:19:09,630 --> 00:19:12,360
for maybe someone in your
household to write code like this,

362
00:19:12,360 --> 00:19:15,402
connect to your phone secretly at
night when you're not paying attention,

363
00:19:15,402 --> 00:19:18,490
and figure out, potentially,
what your code actually is.

364
00:19:18,490 --> 00:19:21,535
So what would be better
than using just digits?

365
00:19:21,535 --> 00:19:22,410
What would be better?

366
00:19:22,410 --> 00:19:25,118
Well, why don't we use letters of
the alphabet, English alphabet,

367
00:19:25,118 --> 00:19:26,310
for today's purposes?

368
00:19:26,310 --> 00:19:31,110
And in the English alphabet, we have
more letters than we have numbers.

369
00:19:31,110 --> 00:19:32,875
So how might we think about this?

370
00:19:32,875 --> 00:19:34,500
Let's go ahead and ask a question here.

371
00:19:34,500 --> 00:19:36,960
If you change your
phone after today to use

372
00:19:36,960 --> 00:19:43,810
four letters of the English alphabet
instead of using numbers alone,

373
00:19:43,810 --> 00:19:45,940
how many possibilities are there then?

374
00:19:45,940 --> 00:19:48,910
Well, let me go ahead and open up
a different poll question here,

375
00:19:48,910 --> 00:19:54,420
which asks this time, how many
4-letter passcodes are possible?

376
00:19:54,420 --> 00:19:56,710
And we'll see what folks
think and answer to this,

377
00:19:56,710 --> 00:19:58,300
as the answers begin to come in.

378
00:19:58,300 --> 00:20:00,880


379
00:20:00,880 --> 00:20:02,805
To be fair, I have not
qualified one thing.

380
00:20:02,805 --> 00:20:04,930
So you might have to be
making certain assumptions.

381
00:20:04,930 --> 00:20:07,930
There are indeed 26 letters
of the English alphabet.

382
00:20:07,930 --> 00:20:10,720
However, there's
uppercase and lowercase.

383
00:20:10,720 --> 00:20:13,300
So if you allow the user
to type in something case

384
00:20:13,300 --> 00:20:16,010
sensitively, so to speak,
where case matters,

385
00:20:16,010 --> 00:20:19,660
it's not 26 possibilities for
each of those four characters.

386
00:20:19,660 --> 00:20:22,130
It's instead 52 possibilities.

387
00:20:22,130 --> 00:20:24,940
So it looks like an
overwhelming number of you, 78%

388
00:20:24,940 --> 00:20:27,790
think there's some seven
million possibilities when

389
00:20:27,790 --> 00:20:29,590
using 4-letter passcodes.

390
00:20:29,590 --> 00:20:33,890
About 11% of you think that
52,000 are all of the passcodes.

391
00:20:33,890 --> 00:20:35,570
So let's go ahead and do the quick math.

392
00:20:35,570 --> 00:20:38,320
Again, it doesn't need to be
particularly sophisticated, the math.

393
00:20:38,320 --> 00:20:41,860
Let me go ahead and open up
this time, similar approach

394
00:20:41,860 --> 00:20:45,082
to this problem, whereby if we
have four letters of the alphabet,

395
00:20:45,082 --> 00:20:47,290
and let's assume case
sensitivity, which, to be fair,

396
00:20:47,290 --> 00:20:49,390
you might not have
assumed, well, then I think

397
00:20:49,390 --> 00:20:53,140
we have 52 possibilities
times 52 times 52 times

398
00:20:53,140 --> 00:20:57,970
52 for each of the four
letters in your passcode.

399
00:20:57,970 --> 00:20:59,860
And if you multiply that out-- boom--

400
00:20:59,860 --> 00:21:03,740
you indeed get seven
million plus possibilities.

401
00:21:03,740 --> 00:21:05,830
So consider the takeaway here.

402
00:21:05,830 --> 00:21:10,720
If you are currently using a passcode
that's four digits, purely numeric,

403
00:21:10,720 --> 00:21:14,980
you have only 10,000 digits between
you and some adversary hacking

404
00:21:14,980 --> 00:21:16,510
into your phone potentially.

405
00:21:16,510 --> 00:21:20,530
If you change your 4-digit
passcode to be a 4-letter passcode,

406
00:21:20,530 --> 00:21:23,980
then you've got seven
million possible passcodes

407
00:21:23,980 --> 00:21:25,420
between you and the adversary.

408
00:21:25,420 --> 00:21:26,660
Now, why is this better?

409
00:21:26,660 --> 00:21:29,710
Well, again, whether they're
using a robot or using code,

410
00:21:29,710 --> 00:21:32,912
it's just going to take them more
time to hack into your device.

411
00:21:32,912 --> 00:21:34,870
And again, at that point,
if it's going to take

412
00:21:34,870 --> 00:21:36,703
them that much time,
that much effort, maybe

413
00:21:36,703 --> 00:21:41,080
even that much money to hack into your
phone, you, relative to other people

414
00:21:41,080 --> 00:21:43,720
might indeed be more secure
because it's probably

415
00:21:43,720 --> 00:21:46,990
going to be easier for that adversary
to go steal someone else's phone

416
00:21:46,990 --> 00:21:49,000
and try to get into that one instead.

417
00:21:49,000 --> 00:21:51,820
Well, let's consider what
this does in actual code.

418
00:21:51,820 --> 00:21:54,970
Let me go back to my Mac here.

419
00:21:54,970 --> 00:21:58,000
And let me go ahead and open
up that same file as before.

420
00:21:58,000 --> 00:22:00,500
And let me go ahead and
change something as follows.

421
00:22:00,500 --> 00:22:04,630
Instead of using just digits, let me use
what I'm going to call ASCII letters.

422
00:22:04,630 --> 00:22:07,480
Families who are not
familiar with CS, ASCII

423
00:22:07,480 --> 00:22:11,080
just refers to essentially all of
the printable letters of the alphabet

424
00:22:11,080 --> 00:22:15,430
that you would typically see in English,
so A through Z, capital and lowercase

425
00:22:15,430 --> 00:22:15,970
here.

426
00:22:15,970 --> 00:22:18,345
And I'm going to go ahead and
change my mention of digits

427
00:22:18,345 --> 00:22:20,300
here to be ASCII letters as well.

428
00:22:20,300 --> 00:22:22,390
So again, the program
is almost identical.

429
00:22:22,390 --> 00:22:27,010
But it's going to use all 52 uppercase
and lowercase English letters instead

430
00:22:27,010 --> 00:22:28,930
of all 10 digits.

431
00:22:28,930 --> 00:22:30,350
Let me save this file.

432
00:22:30,350 --> 00:22:33,130
Let me rerun python of crack.py.

433
00:22:33,130 --> 00:22:36,910
And this time I actually have a
moment to walk over to the screen

434
00:22:36,910 --> 00:22:40,810
and point out now that we're just
now through the lower case zs.

435
00:22:40,810 --> 00:22:43,000
Now we're going through
all the possible passcodes

436
00:22:43,000 --> 00:22:44,530
that start with capital letters.

437
00:22:44,530 --> 00:22:46,000
It's still pretty fast.

438
00:22:46,000 --> 00:22:48,940
This is maybe, what,
10 seconds later done?

439
00:22:48,940 --> 00:22:52,690
We went from AAAA to ZZZZ.

440
00:22:52,690 --> 00:22:54,040
So we've raised the bar.

441
00:22:54,040 --> 00:22:58,330
And again, the security of our
phone in this case is arguably more.

442
00:22:58,330 --> 00:23:00,190
It's higher because
now it's going to take

443
00:23:00,190 --> 00:23:04,870
the adversary more time or more effort
to actually hack into our device.

444
00:23:04,870 --> 00:23:07,120
Well, let's consider, perhaps,
another question, then.

445
00:23:07,120 --> 00:23:11,410
What if we generalize it
further to be characters?

446
00:23:11,410 --> 00:23:13,277
And those of you among
families, perhaps,

447
00:23:13,277 --> 00:23:15,860
might not know the distinction
between characters and letters.

448
00:23:15,860 --> 00:23:17,830
So let me open this
up to the floor here.

449
00:23:17,830 --> 00:23:20,140
When you register for
a website these days,

450
00:23:20,140 --> 00:23:22,750
it's somewhat annoying because
those websites typically

451
00:23:22,750 --> 00:23:25,840
force you to choose a good password.

452
00:23:25,840 --> 00:23:28,990
And what do they typically
mean by good password?

453
00:23:28,990 --> 00:23:33,130
What does your password these days often
have to contain before the website even

454
00:23:33,130 --> 00:23:35,060
lets you proceed?

455
00:23:35,060 --> 00:23:36,580
Any thoughts?

456
00:23:36,580 --> 00:23:37,240
And let's see.

457
00:23:37,240 --> 00:23:38,240
Brian, who do we have?

458
00:23:38,240 --> 00:23:39,492
How about Dax?

459
00:23:39,492 --> 00:23:40,450
What are your thoughts?

460
00:23:40,450 --> 00:23:44,245
DAX: Eight characters at the very
least, number, and a capital.

461
00:23:44,245 --> 00:23:46,370
DAVID J. MALAN: So at least
a number and character.

462
00:23:46,370 --> 00:23:47,260
So combine the two.

463
00:23:47,260 --> 00:23:47,990
I like that.

464
00:23:47,990 --> 00:23:53,290
So instead of 26 or 52 or 10,
we instead have, maybe, 62

465
00:23:53,290 --> 00:23:54,940
if we combine letters and numbers.

466
00:23:54,940 --> 00:23:56,910
Other thoughts on what
websites typically--

467
00:23:56,910 --> 00:23:57,910
DAX: Special characters.

468
00:23:57,910 --> 00:23:59,327
DAVID J. MALAN: --force you to do?

469
00:23:59,327 --> 00:24:02,280
DAX: Special characters--
asterisk, hashtag, dollar sign.

470
00:24:02,280 --> 00:24:05,413
DAVID J. MALAN: OK, so special
characters or punctuation characters.

471
00:24:05,413 --> 00:24:06,580
So maybe it's a hash symbol.

472
00:24:06,580 --> 00:24:09,698
Maybe it's an exclamation point,
a parenthesis, a comma, a period,

473
00:24:09,698 --> 00:24:11,365
something else-- yeah, so these symbols.

474
00:24:11,365 --> 00:24:13,870
And frankly, I get as
annoyed as you probably

475
00:24:13,870 --> 00:24:16,755
do when these websites
annoy you and say, no,

476
00:24:16,755 --> 00:24:18,130
that you can't use that password.

477
00:24:18,130 --> 00:24:19,570
No, you can't use that password.

478
00:24:19,570 --> 00:24:21,945
You need to choose something
that's much harder to guess.

479
00:24:21,945 --> 00:24:26,240
But indeed, if we add punctuation to
the mix, I think we can do even better.

480
00:24:26,240 --> 00:24:29,922
In fact, a character, therefore,
is any type of character.

481
00:24:29,922 --> 00:24:30,880
Maybe it's punctuation.

482
00:24:30,880 --> 00:24:31,713
Maybe it's a letter.

483
00:24:31,713 --> 00:24:33,980
Maybe it's a digit,
unlike just letters alone.

484
00:24:33,980 --> 00:24:36,040
So if we have four
characters, it turns out

485
00:24:36,040 --> 00:24:39,670
that typically, at least in ASCII, the
system that CS50 students will know,

486
00:24:39,670 --> 00:24:44,050
computers typically use, there's
94 possibilities for each symbol

487
00:24:44,050 --> 00:24:47,590
because you've got 10
digits, zero through nine.

488
00:24:47,590 --> 00:24:51,340
You've got 26 lowercase letters,
26 uppercase letters-- and then

489
00:24:51,340 --> 00:24:55,960
if you count them up on an English
keyboard, 32 characters more that

490
00:24:55,960 --> 00:24:58,690
represent punctuation,
like, hashes and exclamation

491
00:24:58,690 --> 00:25:00,010
points and commas and periods.

492
00:25:00,010 --> 00:25:03,080
So if you have 94 possibilities
for each of those symbols,

493
00:25:03,080 --> 00:25:08,840
it turns out that you then have a
total of 78 million possible passcodes.

494
00:25:08,840 --> 00:25:10,280
And that's pretty good.

495
00:25:10,280 --> 00:25:12,890
Now we're really raising
the bar to the adversary

496
00:25:12,890 --> 00:25:18,140
because now they have to waste even more
time trying to hack into your passcode.

497
00:25:18,140 --> 00:25:21,170
And in fact, let me go ahead and
simulate that with some actual code.

498
00:25:21,170 --> 00:25:23,990
Let me go ahead and open up
my same program as before.

499
00:25:23,990 --> 00:25:27,290
And this time let me go ahead and
import not just ASCII letters,

500
00:25:27,290 --> 00:25:30,560
but also digits, and also
literally, punctuation.

501
00:25:30,560 --> 00:25:33,200
The code I'm writing in this
language called Python literally

502
00:25:33,200 --> 00:25:35,600
gives me access to all
printable punctuation

503
00:25:35,600 --> 00:25:38,240
by just importing it with
this first line of code.

504
00:25:38,240 --> 00:25:41,390
And I just need to change
one line of code down here.

505
00:25:41,390 --> 00:25:47,930
I need to actually say ASCII letters
plus digits plus punctuation.

506
00:25:47,930 --> 00:25:52,160
So this is Python shorthand
notation for joining multiple lists.

507
00:25:52,160 --> 00:25:55,580
Those CS50 students among you will know
that you can join two lists, perhaps,

508
00:25:55,580 --> 00:25:57,710
in this way, using what
looks like concatenation.

509
00:25:57,710 --> 00:25:59,940
But with lists, it
combines them all together.

510
00:25:59,940 --> 00:26:01,760
But I'm still going to
do of length 4 here.

511
00:26:01,760 --> 00:26:03,620
Now let me go ahead
and save this program

512
00:26:03,620 --> 00:26:05,990
and rerun it as python of crack.py.

513
00:26:05,990 --> 00:26:10,550
And now I can frankly take my
time walking over to the screen

514
00:26:10,550 --> 00:26:14,630
because now what you're seeing on
the screen is four possible symbols.

515
00:26:14,630 --> 00:26:18,230
But it's including 32 possible
punctuation symbols, which

516
00:26:18,230 --> 00:26:20,630
means this list is much longer, right?

517
00:26:20,630 --> 00:26:22,700
At this point in the
story, we were already

518
00:26:22,700 --> 00:26:26,280
through all of the lowercase
letters up through Z a moment ago.

519
00:26:26,280 --> 00:26:32,900
Now we're only at the Ms,
Ns, Os, Ps, which is to say,

520
00:26:32,900 --> 00:26:35,480
that if my Mac weren't just
printing this on the screen,

521
00:26:35,480 --> 00:26:38,870
but were instead connected to your
phone that I stole and somehow

522
00:26:38,870 --> 00:26:41,990
sending all of these possible
passcodes into your phone,

523
00:26:41,990 --> 00:26:44,930
it would be taking this
much time to actually solve.

524
00:26:44,930 --> 00:26:47,630
Now, to be fair, we're
almost at the lowercase zs.

525
00:26:47,630 --> 00:26:52,400
So if we stall for a minute or two
longer, this program, too, will finish.

526
00:26:52,400 --> 00:26:57,420
So even 78 million possibilities
is not all that impressive.

527
00:26:57,420 --> 00:27:00,810
And so I daresay that we should
do even better than this.

528
00:27:00,810 --> 00:27:05,420
So what might be better than
four characters for a password?

529
00:27:05,420 --> 00:27:06,980
Any thoughts or volunteers?

530
00:27:06,980 --> 00:27:10,790
What would be a better password
than four characters, where,

531
00:27:10,790 --> 00:27:16,530
again, each character is a letter,
a number, or a punctuation symbol?

532
00:27:16,530 --> 00:27:17,530
The list is pretty good.

533
00:27:17,530 --> 00:27:19,238
But I think we can do
better because even

534
00:27:19,238 --> 00:27:22,290
this will be done in under a minute.

535
00:27:22,290 --> 00:27:23,850
Yeah, thoughts about it, Leo?

536
00:27:23,850 --> 00:27:25,590
LEO: Right.

537
00:27:25,590 --> 00:27:28,310
Have a longer password to use,
like, at least eight characters.

538
00:27:28,310 --> 00:27:29,310
DAVID J. MALAN: Perfect.

539
00:27:29,310 --> 00:27:31,268
So have a longer password
using at least eight.

540
00:27:31,268 --> 00:27:33,777
And notice here, we're even
now going through the numbers.

541
00:27:33,777 --> 00:27:35,860
But we're almost done, it
seems, with the numbers.

542
00:27:35,860 --> 00:27:37,420
But now we're going through punctuation.

543
00:27:37,420 --> 00:27:39,837
But again, if I give this a
little more time-- and I think

544
00:27:39,837 --> 00:27:41,018
I was a little overzealous.

545
00:27:41,018 --> 00:27:42,810
Under a minute probably
isn't going to fly.

546
00:27:42,810 --> 00:27:45,570
But certainly, by the end of
class, that will have been done.

547
00:27:45,570 --> 00:27:48,660
But what if we do a little
better and use eight characters?

548
00:27:48,660 --> 00:27:50,970
Well, eight characters is
going to take even longer.

549
00:27:50,970 --> 00:27:54,403
But let's go ahead and ask you all
how much longer this might take.

550
00:27:54,403 --> 00:27:56,820
Let me go ahead and open up a
somewhat different question,

551
00:27:56,820 --> 00:27:58,300
but similar in spirit.

552
00:27:58,300 --> 00:28:01,300
In just a moment that will
appear on your screen.

553
00:28:01,300 --> 00:28:05,010
And the question here is going to be
how many 8-character passcodes are

554
00:28:05,010 --> 00:28:06,060
possible?

555
00:28:06,060 --> 00:28:08,280
And this time I'm waving my hand at it.

556
00:28:08,280 --> 00:28:11,310
I didn't even bother doing
the math precisely yet.

557
00:28:11,310 --> 00:28:13,560
But I'm proposing that
it's roughly a million,

558
00:28:13,560 --> 00:28:18,090
a billion, a trillion, a
quadrillion, a quintillion.

559
00:28:18,090 --> 00:28:20,737
Some of you are perhaps
noticing a pattern here.

560
00:28:20,737 --> 00:28:22,320
And you went straight for quintillion.

561
00:28:22,320 --> 00:28:24,790
That bar jumped up really fast.

562
00:28:24,790 --> 00:28:26,160
So maybe you're right.

563
00:28:26,160 --> 00:28:27,480
Good instincts, perhaps.

564
00:28:27,480 --> 00:28:29,550
It looks like we're getting equilibrium.

565
00:28:29,550 --> 00:28:32,190
About 60% of you think
it's 1 quintillion.

566
00:28:32,190 --> 00:28:34,350
25% of you think it's a quadrillion.

567
00:28:34,350 --> 00:28:36,600
And then fewer and fewer for the others.

568
00:28:36,600 --> 00:28:39,060
Well, let's take a look at
what the actual answer is.

569
00:28:39,060 --> 00:28:42,640
Give me just a moment to actually
do out the math here on my screen.

570
00:28:42,640 --> 00:28:45,120
And if we do out the
math on my screen here,

571
00:28:45,120 --> 00:28:47,760
we'll see, of course, that
we need to do some more math.

572
00:28:47,760 --> 00:28:52,620
We need to do 94 times itself
eight times instead of just four,

573
00:28:52,620 --> 00:28:55,350
to Leo's suggestion of using
eight possible symbols.

574
00:28:55,350 --> 00:28:58,020
And if you do this out, I
had to think about this.

575
00:28:58,020 --> 00:29:02,880
This in fact is, let's see, we've
got millions, billions, trillions,

576
00:29:02,880 --> 00:29:04,200
quadrillions.

577
00:29:04,200 --> 00:29:04,860
Gotcha.

578
00:29:04,860 --> 00:29:07,470
So it wasn't the biggest
option on the list.

579
00:29:07,470 --> 00:29:09,810
The answer is indeed quadrillion.

580
00:29:09,810 --> 00:29:12,330
So 6 quadrillion, if you will.

581
00:29:12,330 --> 00:29:15,120
But-- but-- but those
of you who are fans

582
00:29:15,120 --> 00:29:18,765
of having quintillion possibilities,
which is pretty, pretty

583
00:29:18,765 --> 00:29:21,390
secure because it's just going
to take the adversary way longer

584
00:29:21,390 --> 00:29:26,910
to hack into your password, well,
all it takes to go from 6 quadrillion

585
00:29:26,910 --> 00:29:31,210
to some number of quintillion
is just two more characters.

586
00:29:31,210 --> 00:29:35,070
So in fact, if Leo had proposed
not an 8-character passcode,

587
00:29:35,070 --> 00:29:39,300
but a 10-character passcode, we
actually would have hit quintillions.

588
00:29:39,300 --> 00:29:40,890
So life gets interesting.

589
00:29:40,890 --> 00:29:44,610
Life gets more secure, the longer
and longer and more complicated

590
00:29:44,610 --> 00:29:46,380
these passcodes get.

591
00:29:46,380 --> 00:29:49,140
All right, so by logic,
then, you should all probably

592
00:29:49,140 --> 00:29:51,210
have passcodes that
are not eight, not 10.

593
00:29:51,210 --> 00:29:53,280
Maybe they're 20 characters long.

594
00:29:53,280 --> 00:29:55,350
Maybe they're 100 characters long.

595
00:29:55,350 --> 00:29:58,920
But here we see another theme
in security, that of trade-offs.

596
00:29:58,920 --> 00:30:03,510
Like, the end all is probably
not to be as secure as possible,

597
00:30:03,510 --> 00:30:05,850
but to be as secure as
possible conditional

598
00:30:05,850 --> 00:30:08,020
on some other goals you might have.

599
00:30:08,020 --> 00:30:10,500
So let me ask this,
what's the trade-off here?

600
00:30:10,500 --> 00:30:15,240
In making your password longer and
longer and more and more complicated,

601
00:30:15,240 --> 00:30:18,270
what price do you pay as the human?

602
00:30:18,270 --> 00:30:19,530
What's the downside?

603
00:30:19,530 --> 00:30:22,350
In computer science, as in
life, there's always a catch.

604
00:30:22,350 --> 00:30:24,070
There's always a cost.

605
00:30:24,070 --> 00:30:27,840
So what's the cost when you make
your passcode more and more secure?

606
00:30:27,840 --> 00:30:28,620
Any thoughts?

607
00:30:28,620 --> 00:30:29,323
Let see.

608
00:30:29,323 --> 00:30:30,240
Who do we have, Brian?

609
00:30:30,240 --> 00:30:32,190
Over to Jenny?

610
00:30:32,190 --> 00:30:32,940
What do you think?

611
00:30:32,940 --> 00:30:36,480
JENNY: Yeah, I feel that it is
very difficult for a human being

612
00:30:36,480 --> 00:30:38,100
to remember such a long password.

613
00:30:38,100 --> 00:30:41,910
And due to that, we even store those
long passwords somewhere in the system

614
00:30:41,910 --> 00:30:45,267
itself so that we can use that whenever
we have to log in into the system.

615
00:30:45,267 --> 00:30:47,100
DAVID J. MALAN: Yeah,
there's this trade-off

616
00:30:47,100 --> 00:30:48,660
of just remembering the darn things.

617
00:30:48,660 --> 00:30:49,950
And you make a perfect point.

618
00:30:49,950 --> 00:30:54,527
If I can get on my soapbox again, if you
are among those people who have pretty

619
00:30:54,527 --> 00:30:57,610
good passwords, and by good passwords,
I mean, some numbers, some letters,

620
00:30:57,610 --> 00:31:02,430
some punctuation, but it's written on
a Post-It note on your monitor at work,

621
00:31:02,430 --> 00:31:06,540
or maybe it's slightly more cleverly
written in a Microsoft Word file

622
00:31:06,540 --> 00:31:08,910
in your hard drive, or
maybe it's in a Google Doc,

623
00:31:08,910 --> 00:31:11,610
or maybe it's even on a piece
of paper in your drawer--

624
00:31:11,610 --> 00:31:14,740
you're just exposing yourself
to other threats, of course.

625
00:31:14,740 --> 00:31:18,123
But here, too, is a sociological
consideration or just a policy

626
00:31:18,123 --> 00:31:20,790
consideration, whether you're
running a business or a university

627
00:31:20,790 --> 00:31:23,370
or just a household with
multiple family members.

628
00:31:23,370 --> 00:31:25,140
What should your own policies be?

629
00:31:25,140 --> 00:31:28,170
Because arguably it's not
Jenny's fault, it's not our fault

630
00:31:28,170 --> 00:31:31,170
if we are resorting to
writing things down on paper

631
00:31:31,170 --> 00:31:34,380
if our passwords are so
darn hard to remember.

632
00:31:34,380 --> 00:31:36,870
And moreover, I haven't even
made the suggestion yet,

633
00:31:36,870 --> 00:31:39,150
but if you are one of
those people in life

634
00:31:39,150 --> 00:31:42,510
who is using the same
password on multiple devices

635
00:31:42,510 --> 00:31:46,620
or on multiple websites or on
multiple apps, you are bad.

636
00:31:46,620 --> 00:31:48,930
Like, you are also doing something bad.

637
00:31:48,930 --> 00:31:49,590
Why?

638
00:31:49,590 --> 00:31:52,770
Because if any one of those
apps or websites is compromised

639
00:31:52,770 --> 00:31:55,080
and your password gets out,
whether it's "iloveyou,"

640
00:31:55,080 --> 00:31:57,750
quote unquote, or something
much more complicated,

641
00:31:57,750 --> 00:32:01,680
all an adversary has to do
now is try that same password

642
00:32:01,680 --> 00:32:02,910
on your other accounts.

643
00:32:02,910 --> 00:32:06,372
And so you're just exposing yourself
to more risk by reusing passwords.

644
00:32:06,372 --> 00:32:08,580
But to Jenny's point here,
my God, where does it end?

645
00:32:08,580 --> 00:32:12,420
Now I need a really long random
password on this website, this one,

646
00:32:12,420 --> 00:32:14,500
and this one, and this
app, all over the place.

647
00:32:14,500 --> 00:32:18,300
I mean, honestly, I as a human certainly
can't remember all of those passwords.

648
00:32:18,300 --> 00:32:21,640
And even if I could, I feel like there's
better things in life to be remembering

649
00:32:21,640 --> 00:32:24,650
than passwords for accounts like this.

650
00:32:24,650 --> 00:32:26,170
So there's surely a trade-off here.

651
00:32:26,170 --> 00:32:30,790
But again, the goal is to keep the
adversary out with some probability,

652
00:32:30,790 --> 00:32:33,460
not necessarily out in the absolute.

653
00:32:33,460 --> 00:32:39,040
So what else can we do to prevent the
adversary from hacking into our systems

654
00:32:39,040 --> 00:32:42,880
so that I can have a somewhat
easier, more memorable passcode,

655
00:32:42,880 --> 00:32:44,110
but at least keep them out?

656
00:32:44,110 --> 00:32:45,860
Well, here's a screenshot
of something you

657
00:32:45,860 --> 00:32:48,100
might have done by
accident, perhaps late

658
00:32:48,100 --> 00:32:51,010
at night when a little groggy,
or a little blurry-eyed,

659
00:32:51,010 --> 00:32:54,670
trying to type in your password
incorrectly too many times.

660
00:32:54,670 --> 00:32:56,980
In fact, by a show of physical
hands, how many people

661
00:32:56,980 --> 00:33:01,840
have locked yourself out of your phone
before by typing in the wrong password

662
00:33:01,840 --> 00:33:02,740
too many times?

663
00:33:02,740 --> 00:33:04,870
I did it, like, literally
just the other day.

664
00:33:04,870 --> 00:33:07,910
And so on iPhone, for instance, it
looks a little something like this.

665
00:33:07,910 --> 00:33:11,660
And if we zoom in, notice that
it's saying, try again in 1 minute.

666
00:33:11,660 --> 00:33:14,570
So you don't have to get rid
of the phone and start over.

667
00:33:14,570 --> 00:33:17,050
But the iPhone is telling
you to come back in a minute.

668
00:33:17,050 --> 00:33:19,960
And if we look at, for instance,
Android, something similar--

669
00:33:19,960 --> 00:33:22,300
your Android wallpaper
will differ, certainly.

670
00:33:22,300 --> 00:33:25,300
But down here, for instance,
it says too many attempts.

671
00:33:25,300 --> 00:33:26,012
Try again later.

672
00:33:26,012 --> 00:33:28,720
I mean, that's a little infuriating
because if I pick up my phone

673
00:33:28,720 --> 00:33:30,130
now, I want to get in now.

674
00:33:30,130 --> 00:33:31,660
Well, when the heck is later?

675
00:33:31,660 --> 00:33:35,600
So putting that aside,
what's the takeaway here?

676
00:33:35,600 --> 00:33:39,005
Why are Apple and why
are Google doing this?

677
00:33:39,005 --> 00:33:42,130
Because I bet all of you, if you've
ever locked yourself out of your phone,

678
00:33:42,130 --> 00:33:45,280
are super annoyed at that moment
in time and probably don't

679
00:33:45,280 --> 00:33:47,280
appreciate Apple or Google.

680
00:33:47,280 --> 00:33:49,030
But what's the upside
of what they've just

681
00:33:49,030 --> 00:33:53,350
done when they lock you out
of your phone for having

682
00:33:53,350 --> 00:33:56,800
guessed your password incorrectly?

683
00:33:56,800 --> 00:34:00,460
Why is this arguably a feature
and not a bug, a mistake?

684
00:34:00,460 --> 00:34:01,090
Sam?

685
00:34:01,090 --> 00:34:04,895
SAM: Yeah, it's used to decrease the
chances of a successful brute force

686
00:34:04,895 --> 00:34:05,395
attack.

687
00:34:05,395 --> 00:34:08,979
DAVID J. MALAN: And how does it decrease
the chance of that, would you say?

688
00:34:08,979 --> 00:34:15,310
SAM: Because it makes the attacker
have to commit more tries before they

689
00:34:15,310 --> 00:34:17,380
can successfully get into the phone.

690
00:34:17,380 --> 00:34:18,969
So it decreases the chances.

691
00:34:18,969 --> 00:34:20,090
DAVID J. MALAN: Exactly.

692
00:34:20,090 --> 00:34:22,840
So this is a very common
principle in security.

693
00:34:22,840 --> 00:34:26,590
And it was pointed out earlier,
too, just slow the adversary down.

694
00:34:26,590 --> 00:34:28,760
We don't have to rethink
the problem of security.

695
00:34:28,760 --> 00:34:31,060
We don't have to redesign
passwords necessarily.

696
00:34:31,060 --> 00:34:33,219
But we should make it
harder for the adversary

697
00:34:33,219 --> 00:34:36,909
to log in, ideally, without making
it harder for you and I to log

698
00:34:36,909 --> 00:34:37,960
in to our own devices.

699
00:34:37,960 --> 00:34:41,650
So consider the simplest
passcode that had four digits.

700
00:34:41,650 --> 00:34:45,010
A 4-digit passcode, there
were 10,000 possibilities.

701
00:34:45,010 --> 00:34:47,980
A computer, a robot could guess
all of those pretty quickly.

702
00:34:47,980 --> 00:34:51,639
But what if after typing in
the wrong passcode three times

703
00:34:51,639 --> 00:34:55,780
or maybe ten times, some small number
of times, what if the iPhone or Android

704
00:34:55,780 --> 00:34:59,560
phone locks you out for a minute,
just like iPhone did a moment ago?

705
00:34:59,560 --> 00:35:03,040
Well, that might mean, even though
there's only 10,000 possibilities,

706
00:35:03,040 --> 00:35:06,040
maybe it will take the
adversary 10,000 minutes

707
00:35:06,040 --> 00:35:10,820
to track your password because they
keep getting slowed down every time

708
00:35:10,820 --> 00:35:12,070
they type in an incorrect one.

709
00:35:12,070 --> 00:35:13,403
And maybe it's not quite 10,000.

710
00:35:13,403 --> 00:35:15,350
It's some factor of that.

711
00:35:15,350 --> 00:35:17,020
But you can slow them down in that way.

712
00:35:17,020 --> 00:35:21,760
Maybe you have a 10-character passcode
with 78 quadrillion possibilities.

713
00:35:21,760 --> 00:35:25,330
And imagine the phone just
slows you down 1 second.

714
00:35:25,330 --> 00:35:28,120
Maybe you can only type in
one passcode per second.

715
00:35:28,120 --> 00:35:29,680
That sounds pretty fast.

716
00:35:29,680 --> 00:35:33,730
But 78 quadrillion
seconds is crazy long.

717
00:35:33,730 --> 00:35:36,880
And so even that kind of
slowdown might very well

718
00:35:36,880 --> 00:35:39,580
be enough to keep the adversary out.

719
00:35:39,580 --> 00:35:43,398
And so if you don't have features like
this enabled on, really, any device,

720
00:35:43,398 --> 00:35:44,440
you should look for them.

721
00:35:44,440 --> 00:35:47,860
Nowadays, thankfully, they tend
to come pre-configured for this.

722
00:35:47,860 --> 00:35:49,810
But there is a downside.

723
00:35:49,810 --> 00:35:50,997
There is a downside.

724
00:35:50,997 --> 00:35:53,080
You shouldn't just turn
on these kinds of defenses

725
00:35:53,080 --> 00:35:56,800
blindly because what's the downside
of keeping this feature enabled

726
00:35:56,800 --> 00:35:59,950
or leaving it enabled--

727
00:35:59,950 --> 00:36:03,970
those are the same things-- or enabling
it, if it's not already enabled?

728
00:36:03,970 --> 00:36:06,310
What's the downside here, to be clear?

729
00:36:06,310 --> 00:36:10,750
Because none of our advice
today will be 100% a win.

730
00:36:10,750 --> 00:36:11,500
David?

731
00:36:11,500 --> 00:36:13,780
DAVID: Well, if you
forget your password,

732
00:36:13,780 --> 00:36:16,780
that means it's going to take longer
for you to access your phone again.

733
00:36:16,780 --> 00:36:20,140
DAVID J. MALAN: Yeah, it's going to take
you, the user, the owner of the device,

734
00:36:20,140 --> 00:36:21,400
even longer to log in.

735
00:36:21,400 --> 00:36:25,060
And I'll admit, too, I have on multiple
occasions not locked myself out once.

736
00:36:25,060 --> 00:36:25,978
I then got stubborn.

737
00:36:25,978 --> 00:36:27,520
And I think my anger level just rose.

738
00:36:27,520 --> 00:36:30,640
So I started typing in more angrily,
and therefore making more mistakes.

739
00:36:30,640 --> 00:36:33,070
And what Apple and
Google do is they have

740
00:36:33,070 --> 00:36:35,380
what you might describe as
exponential backoff, which

741
00:36:35,380 --> 00:36:38,847
is a fancy way of saying, the first
time you get penalized one minute.

742
00:36:38,847 --> 00:36:40,180
Now you have to wait one minute.

743
00:36:40,180 --> 00:36:43,030
If you screw up again, then
you have to wait two minutes.

744
00:36:43,030 --> 00:36:45,023
If you screw up again,
maybe it's five minutes.

745
00:36:45,023 --> 00:36:45,940
Maybe it's 10 minutes.

746
00:36:45,940 --> 00:36:46,840
Maybe it's an hour.

747
00:36:46,840 --> 00:36:49,715
And I swear, at that point I wanted
to throw my phone across the room

748
00:36:49,715 --> 00:36:51,700
because I couldn't get
into my own device.

749
00:36:51,700 --> 00:36:55,840
And there you start to sacrifice,
of course, usability, right?

750
00:36:55,840 --> 00:37:00,190
If my device is so secure
that even I can't get into it,

751
00:37:00,190 --> 00:37:02,080
then is it really worth having at all?

752
00:37:02,080 --> 00:37:04,780
And so finding that
inflection point is part

753
00:37:04,780 --> 00:37:07,720
of engineering good
secure systems because you

754
00:37:07,720 --> 00:37:10,150
have to find that inflection
point so that your users

755
00:37:10,150 --> 00:37:12,190
are using good passwords and passcodes.

756
00:37:12,190 --> 00:37:16,300
But they're not just taping them
onto the monitor on a Post-It note

757
00:37:16,300 --> 00:37:19,123
or disabling them all together.

758
00:37:19,123 --> 00:37:21,040
All right, let me pause
here to see, are there

759
00:37:21,040 --> 00:37:27,310
any questions about passwords,
passcodes, brute forcing or these kinds

760
00:37:27,310 --> 00:37:30,550
of defenses, given that
passwords are perhaps

761
00:37:30,550 --> 00:37:33,520
our most common defense
against adversaries

762
00:37:33,520 --> 00:37:36,880
accessing hardware and software
that we don't want them to?

763
00:37:36,880 --> 00:37:38,485
Yeah, Dax, question?

764
00:37:38,485 --> 00:37:40,720
DAX: Now so there is
a definite number we

765
00:37:40,720 --> 00:37:43,240
can calculate that for
4-digit numbers this is

766
00:37:43,240 --> 00:37:46,120
the most possible number of outcomes.

767
00:37:46,120 --> 00:37:47,918
But what about biometrics?

768
00:37:47,918 --> 00:37:48,460
Fingerprints?

769
00:37:48,460 --> 00:37:49,845
Face scanning?

770
00:37:49,845 --> 00:37:51,710
DAVID J. MALAN: Yeah,
really good question.

771
00:37:51,710 --> 00:37:53,950
So what about biometrics,
using face scanning?

772
00:37:53,950 --> 00:37:58,397
Like, Apple has face ID these days,
which also annoys me sometimes

773
00:37:58,397 --> 00:37:59,980
if it doesn't quite get my face right.

774
00:37:59,980 --> 00:38:02,230
Or these days if we're
wearing masks, it's

775
00:38:02,230 --> 00:38:03,910
infuriating to use that kind of feature.

776
00:38:03,910 --> 00:38:07,935
But maybe probabilistically, there
are fewer people with exactly

777
00:38:07,935 --> 00:38:09,560
your facial features than someone else.

778
00:38:09,560 --> 00:38:12,060
And so that would be more secure
than picking some passcode.

779
00:38:12,060 --> 00:38:14,770
Sometimes you use
fingerprints or retinal scans

780
00:38:14,770 --> 00:38:17,650
or the distance between your fingers,
all of these different measures

781
00:38:17,650 --> 00:38:21,850
that statistically tend
to not so much uniquely

782
00:38:21,850 --> 00:38:25,508
identify us, but uniquely
identify us all enough.

783
00:38:25,508 --> 00:38:26,800
And there's threats there, too.

784
00:38:26,800 --> 00:38:28,508
A former colleague of
ours, for instance,

785
00:38:28,508 --> 00:38:31,090
had a twin brother who
because of Apple's face ID

786
00:38:31,090 --> 00:38:34,330
was now able to get into his phone by
just picking it up off of the table

787
00:38:34,330 --> 00:38:36,980
because as twins, they both
looked all too similar.

788
00:38:36,980 --> 00:38:39,580
So there's downsides
and upsides there, too.

789
00:38:39,580 --> 00:38:42,070
But biometrics can also
help things so that it's

790
00:38:42,070 --> 00:38:45,130
a factor you have on you
always and not something,

791
00:38:45,130 --> 00:38:48,010
for instance, that you
just only have to remember.

792
00:38:48,010 --> 00:38:51,520
And in fact, that's a perfect
segue to what computer scientists

793
00:38:51,520 --> 00:38:54,217
call two-factor authentication.

794
00:38:54,217 --> 00:38:56,050
In the security world,
security people would

795
00:38:56,050 --> 00:39:01,070
call the passwords we're using
one factor, and something

796
00:39:01,070 --> 00:39:03,380
like biometrics, a second factor.

797
00:39:03,380 --> 00:39:06,350
And indeed, two-factor authentication
means a defense mechanism

798
00:39:06,350 --> 00:39:09,050
against the adversaries that
doesn't rely just on something

799
00:39:09,050 --> 00:39:10,970
you know, like, a password.

800
00:39:10,970 --> 00:39:14,540
It also relies on something
typically that you have, like,

801
00:39:14,540 --> 00:39:18,570
a hand or fingers or
eyes or face or the like,

802
00:39:18,570 --> 00:39:21,980
so that even if someone
compromises your password

803
00:39:21,980 --> 00:39:25,490
and downloads it somewhere from a
database where you've used it before,

804
00:39:25,490 --> 00:39:28,490
they don't necessarily have
access to your eyes and your hands

805
00:39:28,490 --> 00:39:31,500
and your face and the like, unless
they have physical access to you.

806
00:39:31,500 --> 00:39:33,680
So it just narrows the
scope of the threats.

807
00:39:33,680 --> 00:39:35,900
But there's other forms of
two-factor authentication.

808
00:39:35,900 --> 00:39:38,718
For instance, if this sounds
familiar now, and maybe

809
00:39:38,718 --> 00:39:40,760
you don't even call it
two-factor authentication.

810
00:39:40,760 --> 00:39:43,970
It's often called
two-step authentication.

811
00:39:43,970 --> 00:39:47,210
By a show of physical hands, who
has one or more accounts that

812
00:39:47,210 --> 00:39:51,000
uses two factors instead of just one?

813
00:39:51,000 --> 00:39:54,350
Yeah, so here, too, it's good
to see so many hands going up.

814
00:39:54,350 --> 00:39:58,370
But if you do not use
two-factor authentication

815
00:39:58,370 --> 00:40:03,170
for things like your email account or
your bank accounts or your brokerage

816
00:40:03,170 --> 00:40:06,830
accounts or your health
medical accounts,

817
00:40:06,830 --> 00:40:09,110
you really should start
considering doing so.

818
00:40:09,110 --> 00:40:10,880
And what form does this typically take?

819
00:40:10,880 --> 00:40:12,963
Well, let me show a
screenshot here, for instance.

820
00:40:12,963 --> 00:40:14,930
Even if you just have
a simple Gmail account

821
00:40:14,930 --> 00:40:17,570
that you use for work
or for personal use,

822
00:40:17,570 --> 00:40:20,480
you can enable what Google calls
two-step verification, which

823
00:40:20,480 --> 00:40:22,360
is two-factor authentication.

824
00:40:22,360 --> 00:40:24,860
And what you'll be prompted for
when logging into your Gmail

825
00:40:24,860 --> 00:40:29,250
account if you enable this is not
only your username and your password,

826
00:40:29,250 --> 00:40:31,070
but also a 6-digit code.

827
00:40:31,070 --> 00:40:33,710
And six digits doesn't
sound terribly long.

828
00:40:33,710 --> 00:40:36,620
But in this case, the way these
technologies typically work

829
00:40:36,620 --> 00:40:42,200
is that you are sent that 6-digit code
once via email or via text message

830
00:40:42,200 --> 00:40:46,010
or via special app that you install
on your phone or some other device

831
00:40:46,010 --> 00:40:48,170
so that only you have that code.

832
00:40:48,170 --> 00:40:50,060
Only you have that device.

833
00:40:50,060 --> 00:40:51,800
And therefore, only you know that code.

834
00:40:51,800 --> 00:40:54,380
And better yet, these codes expire.

835
00:40:54,380 --> 00:40:57,770
So even if some adversary
intercepts it or sees you typing it

836
00:40:57,770 --> 00:41:00,560
in over your shoulder, you
can only use these codes once,

837
00:41:00,560 --> 00:41:02,750
which makes them even
better than passwords

838
00:41:02,750 --> 00:41:06,680
alone because they expire
after single time use.

839
00:41:06,680 --> 00:41:08,450
And so consider now, again--

840
00:41:08,450 --> 00:41:10,400
and I can't emphasize
this enough-- if you

841
00:41:10,400 --> 00:41:13,242
are of the age where you have
your own bank accounts, again,

842
00:41:13,242 --> 00:41:15,200
brokerage accounts,
anything medically related,

843
00:41:15,200 --> 00:41:17,600
anything that you find
especially important or personal,

844
00:41:17,600 --> 00:41:21,830
like, your own email or chat accounts,
if you're only using a password,

845
00:41:21,830 --> 00:41:24,920
you now as of today already
have the mathematical tools

846
00:41:24,920 --> 00:41:28,010
and the mental model, I
daresay, to figure out just

847
00:41:28,010 --> 00:41:32,780
how easily someone could compromise your
account and get into your information

848
00:41:32,780 --> 00:41:35,637
and take your money or read
your emails or the like.

849
00:41:35,637 --> 00:41:38,720
So you can improve that situation by
just coming up with a better, longer,

850
00:41:38,720 --> 00:41:42,410
more random password that you
remember or memorize in some way,

851
00:41:42,410 --> 00:41:46,820
or additionally, by enabling the
second factor so that you narrow

852
00:41:46,820 --> 00:41:52,710
the number of threats that are
dangerous to you as a result.

853
00:41:52,710 --> 00:41:55,112
So with that said, too, with
two-factor authentication,

854
00:41:55,112 --> 00:41:57,320
there's another thing you
can bring into play when it

855
00:41:57,320 --> 00:41:59,810
comes to managing all your passwords.

856
00:41:59,810 --> 00:42:03,230
I alluded to using Microsoft
Word before or a Post-It note.

857
00:42:03,230 --> 00:42:05,970
There are software
solutions to this, too.

858
00:42:05,970 --> 00:42:09,320
So another defense we would like to
offer up for your consideration today

859
00:42:09,320 --> 00:42:11,510
is what's generally
called a password manager.

860
00:42:11,510 --> 00:42:14,645
This is a piece of software, either
for free or that you pay for,

861
00:42:14,645 --> 00:42:17,300
for your phone or your
laptop or desktop, that

862
00:42:17,300 --> 00:42:19,160
literally manages your passwords.

863
00:42:19,160 --> 00:42:23,750
In its simplest form, think of it like
a spreadsheet, but that's "secure,"

864
00:42:23,750 --> 00:42:25,670
quote unquote, on your own computer.

865
00:42:25,670 --> 00:42:28,970
That is, these password managers--
and here's two popular ones.

866
00:42:28,970 --> 00:42:33,483
onepassword.com is one popular
tool. lastpass.com is another one.

867
00:42:33,483 --> 00:42:35,150
And there's others if you google around.

868
00:42:35,150 --> 00:42:37,970
But I would, as always, read up
on reviews or get second opinions.

869
00:42:37,970 --> 00:42:40,160
Don't just take at face
value what we propose.

870
00:42:40,160 --> 00:42:42,620
But these password managers
are programs that you

871
00:42:42,620 --> 00:42:45,920
type your usernames and passwords into.

872
00:42:45,920 --> 00:42:52,040
And then you save them all behind one
master password, one password that's

873
00:42:52,040 --> 00:42:54,650
really long, hopefully,
really random with lots

874
00:42:54,650 --> 00:42:56,210
of numbers and letters and symbols.

875
00:42:56,210 --> 00:43:00,710
But all you have to remember
is that one main password.

876
00:43:00,710 --> 00:43:04,040
And by entering that password
into your Mac or PC or phone,

877
00:43:04,040 --> 00:43:06,230
you then unlock all of
your other accounts.

878
00:43:06,230 --> 00:43:09,920
And you can then just copy and paste
your actual accounts' usernames

879
00:43:09,920 --> 00:43:10,725
and passwords.

880
00:43:10,725 --> 00:43:12,850
Or these programs also give
you keyboard shortcuts.

881
00:43:12,850 --> 00:43:16,430
So you hit a keyboard command,
and voila, you're automatically

882
00:43:16,430 --> 00:43:17,420
logged into websites.

883
00:43:17,420 --> 00:43:20,000
You don't have to copy/paste
or manually transcribe them.

884
00:43:20,000 --> 00:43:21,860
So to this day, what does this mean?

885
00:43:21,860 --> 00:43:24,230
For me, I use one of
these password managers.

886
00:43:24,230 --> 00:43:25,980
And most of my colleagues do as well.

887
00:43:25,980 --> 00:43:29,660
Many of us, most of us,
don't even know the passwords

888
00:43:29,660 --> 00:43:32,960
we use for various websites
or apps or the like.

889
00:43:32,960 --> 00:43:33,590
Why?

890
00:43:33,590 --> 00:43:35,780
Because we now trust
that the password manager

891
00:43:35,780 --> 00:43:39,710
can, with the click of a button,
generate a really long random password

892
00:43:39,710 --> 00:43:41,870
with lots of numbers,
digits, and punctuation.

893
00:43:41,870 --> 00:43:44,510
And then it will remember it for me.

894
00:43:44,510 --> 00:43:47,870
And I just have to remember
that one main password that's

895
00:43:47,870 --> 00:43:50,430
protecting all of those others.

896
00:43:50,430 --> 00:43:54,890
So that's good in that now I can
practice what I've been preaching.

897
00:43:54,890 --> 00:43:58,330
But there is a downside.

898
00:43:58,330 --> 00:44:01,420
I'm exposing myself to a
new risk or vulnerability.

899
00:44:01,420 --> 00:44:03,760
That is to say, what's
the trade-off here?

900
00:44:03,760 --> 00:44:07,360
Why should you not necessarily
just run off after today's class,

901
00:44:07,360 --> 00:44:11,260
download and install a password
manager, and start using it

902
00:44:11,260 --> 00:44:13,990
without a little bit of thought first.

903
00:44:13,990 --> 00:44:17,080
What's the downside, perhaps?

904
00:44:17,080 --> 00:44:23,580
Yeah, over to Lexlene
if I'm saying it right?

905
00:44:23,580 --> 00:44:30,390
LEXLENE: Yeah, if someone cracks
your password manager password,

906
00:44:30,390 --> 00:44:32,840
then they have access
to all your passwords.

907
00:44:32,840 --> 00:44:35,893
DAVID J. MALAN: Yeah, so really
depends on what the threat here is,

908
00:44:35,893 --> 00:44:37,310
or what you're most worried about.

909
00:44:37,310 --> 00:44:39,350
If someone compromises,
guesses, figures out

910
00:44:39,350 --> 00:44:41,970
your main password that
protects all of the others,

911
00:44:41,970 --> 00:44:44,570
now you've just handed them
all of your accounts at once.

912
00:44:44,570 --> 00:44:46,590
And that's a massive trade-off.

913
00:44:46,590 --> 00:44:48,980
However, if you again
consider the alternative,

914
00:44:48,980 --> 00:44:53,090
coming up with big random passwords and
then memorizing them all, or somewhat

915
00:44:53,090 --> 00:44:55,010
foolishly, writing them
down on a Post-It note

916
00:44:55,010 --> 00:44:56,843
and putting it on your
monitor, the question

917
00:44:56,843 --> 00:45:02,450
shouldn't be is this the
right way to do things,

918
00:45:02,450 --> 00:45:05,702
but really, relatively speaking,
is this a better way to do things?

919
00:45:05,702 --> 00:45:07,910
So you're always going to
be vulnerable to some risk.

920
00:45:07,910 --> 00:45:09,590
Which of those risks do you worry about?

921
00:45:09,590 --> 00:45:12,380
And maybe you can mitigate
that concern by maybe

922
00:45:12,380 --> 00:45:15,920
you could write down your main
password for your password manager

923
00:45:15,920 --> 00:45:20,390
and maybe put it in a physical
vault or a fire locker or the like

924
00:45:20,390 --> 00:45:23,260
that with very low probability
someone else would get access to,

925
00:45:23,260 --> 00:45:25,010
unless they physically
attack that device,

926
00:45:25,010 --> 00:45:27,960
or hide it somewhere in a book
on your shelf or the like.

927
00:45:27,960 --> 00:45:29,510
So that yes, it's vulnerable.

928
00:45:29,510 --> 00:45:33,140
But the odds that someone finds
it might just be relatively low.

929
00:45:33,140 --> 00:45:35,630
But again, this is the
theme, figuring out

930
00:45:35,630 --> 00:45:39,170
what the right balance is for your
accounts and the type of security

931
00:45:39,170 --> 00:45:42,140
that you want to aspire to achieve.

932
00:45:42,140 --> 00:45:43,890
Well, let's consider
a few other defenses.

933
00:45:43,890 --> 00:45:46,932
And we'll leave time at the very end
for questions about particular tools

934
00:45:46,932 --> 00:45:47,632
and techniques.

935
00:45:47,632 --> 00:45:49,340
What's another building
block that we can

936
00:45:49,340 --> 00:45:52,310
bring to bear when it comes to
protecting ourselves online?

937
00:45:52,310 --> 00:45:55,850
So encryption-- CS50 students will
know that encryption refers, again,

938
00:45:55,850 --> 00:46:01,010
to the scrambling of information,
making data look like it's random data,

939
00:46:01,010 --> 00:46:05,000
but by encrypting it with what's called
the key, typically, a key that only you

940
00:46:05,000 --> 00:46:06,890
and the recipient somehow know.

941
00:46:06,890 --> 00:46:10,070
Encryption tends to be the
solution to a lot of our problems.

942
00:46:10,070 --> 00:46:12,650
And indeed, these password
managers typically

943
00:46:12,650 --> 00:46:17,150
additionally encrypt your data so that
even someone who steals your Mac and PC

944
00:46:17,150 --> 00:46:19,370
can't just open up the
program and see it.

945
00:46:19,370 --> 00:46:21,620
All of the data, too,
is similarly encrypted.

946
00:46:21,620 --> 00:46:26,030
Many of you have already been trained or
conditioned by society to at least look

947
00:46:26,030 --> 00:46:30,815
for or hope for or recognize https://.

948
00:46:30,815 --> 00:46:32,425
The s means secure.

949
00:46:32,425 --> 00:46:34,550
That just tends to be a
good thing because it means

950
00:46:34,550 --> 00:46:36,290
a website you're visiting is secure.

951
00:46:36,290 --> 00:46:39,830
It's encrypted, as opposed
to just http, which

952
00:46:39,830 --> 00:46:43,620
was much more common just a few years
ago and is completely unencrypted.

953
00:46:43,620 --> 00:46:48,260
So that is to say if you visit a website
that says just http in the URL, anyone

954
00:46:48,260 --> 00:46:51,960
between you and that website
theoretically can be listening in,

955
00:46:51,960 --> 00:46:55,460
so to speak, on your traffic, the
zeros and ones going back and forth.

956
00:46:55,460 --> 00:46:57,410
Anyone can see what
pages you're visiting.

957
00:46:57,410 --> 00:47:00,260
If you're in some foreign country
visiting sensitive materials,

958
00:47:00,260 --> 00:47:02,840
the government could know
what websites you're visiting

959
00:47:02,840 --> 00:47:05,400
and what content, for
instance, you're reading.

960
00:47:05,400 --> 00:47:07,940
https makes that much harder.

961
00:47:07,940 --> 00:47:09,080
It's not 100%.

962
00:47:09,080 --> 00:47:10,940
There are attacks still
that are possible.

963
00:47:10,940 --> 00:47:12,800
But again, it just raises the bar.

964
00:47:12,800 --> 00:47:15,667
But there's another
technique that's increasingly

965
00:47:15,667 --> 00:47:18,500
being discussed in the media, and
with which you should be familiar,

966
00:47:18,500 --> 00:47:20,690
known as end-to-end encryption.

967
00:47:20,690 --> 00:47:24,890
End-to-end encryption means that when
you're using a third-party service,

968
00:47:24,890 --> 00:47:27,980
typically, whether it's a chat
service, a video conferencing

969
00:47:27,980 --> 00:47:30,320
service or the like,
you're not just encrypting

970
00:47:30,320 --> 00:47:33,590
your traffic, the zeros
and ones, between you

971
00:47:33,590 --> 00:47:39,020
and Google, you and Microsoft, you
and Amazon, or some other third-party.

972
00:47:39,020 --> 00:47:43,310
You are encrypting your data between
you and the person you're talking to.

973
00:47:43,310 --> 00:47:46,580
So WhatsApp, for instance,
the popular messaging tool,

974
00:47:46,580 --> 00:47:48,140
early on had this feature.

975
00:47:48,140 --> 00:47:50,670
And many other chat programs
nowadays have it as well,

976
00:47:50,670 --> 00:47:54,805
including iMessage and Signal
and Telegram and the like.

977
00:47:54,805 --> 00:47:56,930
End-to-end encryption means
that even though you're

978
00:47:56,930 --> 00:48:01,520
using a third-party service, a
company that you may or may not trust,

979
00:48:01,520 --> 00:48:06,050
your communications are communicated
between you and the person

980
00:48:06,050 --> 00:48:08,190
with whom you're speaking.

981
00:48:08,190 --> 00:48:12,260
The company in between, their servers,
even though your data is going through

982
00:48:12,260 --> 00:48:15,530
their servers, cannot
decrypt that information.

983
00:48:15,530 --> 00:48:18,232
They cannot see the
information in its raw form.

984
00:48:18,232 --> 00:48:19,190
So that's a good thing.

985
00:48:19,190 --> 00:48:21,760


986
00:48:21,760 --> 00:48:23,140
So WhatsApp does this, too.

987
00:48:23,140 --> 00:48:28,100
Zoom kind of does this, at
least, only recently does this.

988
00:48:28,100 --> 00:48:31,030
So Zoom, for instance, the technology
that we are all using right now,

989
00:48:31,030 --> 00:48:33,580
actually took some flak,
rightly so, some months

990
00:48:33,580 --> 00:48:36,700
back, when in their marketing literature
on their website, as I recall,

991
00:48:36,700 --> 00:48:40,510
advertised Zoom as offering
end-to-end encryption, which

992
00:48:40,510 --> 00:48:43,750
was false because what
end-to-end encryption means is,

993
00:48:43,750 --> 00:48:47,620
as I described it, between you and the
person with whom you're communicating.

994
00:48:47,620 --> 00:48:50,890
But the marketing
literature at the time was

995
00:48:50,890 --> 00:48:53,410
referring to end-to-end
encryption between you

996
00:48:53,410 --> 00:48:57,430
and Zoom, which is not what security
researchers or computer scientists

997
00:48:57,430 --> 00:49:00,970
or technologists in general would
define end-to-end encryption as.

998
00:49:00,970 --> 00:49:03,130
And so they took some
flak for that, rightly so.

999
00:49:03,130 --> 00:49:05,650
They've begun, though, in
recent weeks, rolling out

1000
00:49:05,650 --> 00:49:08,140
actual end-to-end encryption.

1001
00:49:08,140 --> 00:49:10,270
We are not using it right now.

1002
00:49:10,270 --> 00:49:12,880
It actually makes certain
features harder to use.

1003
00:49:12,880 --> 00:49:14,530
So there, too, there's a trade-off.

1004
00:49:14,530 --> 00:49:17,590
But generally speaking, if you're
having the most intimate or private

1005
00:49:17,590 --> 00:49:22,150
or personal or financial or medical
of communications with people,

1006
00:49:22,150 --> 00:49:27,010
this is another feature you should start
to look for and listen for and expect

1007
00:49:27,010 --> 00:49:28,810
of the tools that you're using.

1008
00:49:28,810 --> 00:49:32,440
And especially when it comes to
censorship in various countries

1009
00:49:32,440 --> 00:49:35,290
and communities, this
is the kind of software

1010
00:49:35,290 --> 00:49:37,330
that's increasingly under
attack by governments

1011
00:49:37,330 --> 00:49:42,730
because they often want backdoor
so that the USA's NSA or FBI

1012
00:49:42,730 --> 00:49:45,130
or some other entity can get
into these communications.

1013
00:49:45,130 --> 00:49:47,650
That's made much more
difficult, in a good way,

1014
00:49:47,650 --> 00:49:53,170
by using end-to-end encryption so that
your communications are indeed secure.

1015
00:49:53,170 --> 00:49:56,757
Well, in our final moments together,
let's focus ultimately on Zoom,

1016
00:49:56,757 --> 00:49:58,090
the very technology we're using.

1017
00:49:58,090 --> 00:49:59,950
Because they've taken
some flak, certainly

1018
00:49:59,950 --> 00:50:02,825
beyond end-to-end encryption, which
you might not have even heard of,

1019
00:50:02,825 --> 00:50:04,210
as just being insecure.

1020
00:50:04,210 --> 00:50:06,640
And a lot of school
systems, a lot of users

1021
00:50:06,640 --> 00:50:09,680
decided some months ago to stop
using Zoom for this reason,

1022
00:50:09,680 --> 00:50:12,040
even though their
business is still booming.

1023
00:50:12,040 --> 00:50:13,630
So is Zoom secure?

1024
00:50:13,630 --> 00:50:15,640
Let's ask one final
question of the group

1025
00:50:15,640 --> 00:50:19,690
here, keeping in mind that we've now
just spent the past hour discussing

1026
00:50:19,690 --> 00:50:21,250
topics of security.

1027
00:50:21,250 --> 00:50:23,990
Let me go ahead and ask
this final question here,

1028
00:50:23,990 --> 00:50:26,920
which will appear on your
screen in just a moment.

1029
00:50:26,920 --> 00:50:32,450
It is quite simply, is Zoom secure?

1030
00:50:32,450 --> 00:50:34,860
All right, let's see how
the responses are coming in.

1031
00:50:34,860 --> 00:50:41,690
I'm seeing 55% no, 16% yes, 28%, unsure.

1032
00:50:41,690 --> 00:50:43,070
So a reasonable spread there.

1033
00:50:43,070 --> 00:50:44,780
Let's take a couple of comments here.

1034
00:50:44,780 --> 00:50:50,120
Among those of you who think Zoom is
secure, why do you think it's secure?

1035
00:50:50,120 --> 00:50:54,080
Would anyone be comfortable raising
a virtual hand so we can call on you,

1036
00:50:54,080 --> 00:50:58,490
or maybe commenting in the chat as
to why you think Zoom is secure?

1037
00:50:58,490 --> 00:51:01,640
Let's see, over to, how about, Sam?

1038
00:51:01,640 --> 00:51:02,390
What do you think?

1039
00:51:02,390 --> 00:51:07,760
SAM: Two days ago, Zoom offered
end-to-end encryption to all the users.

1040
00:51:07,760 --> 00:51:10,730
DAVID J. MALAN: Yeah, so it
was, in fact, that timely.

1041
00:51:10,730 --> 00:51:12,497
Zoom began rolling
out, on a trial basis,

1042
00:51:12,497 --> 00:51:14,580
essentially, end-to-end
encryption with all users.

1043
00:51:14,580 --> 00:51:18,290
So if you are using that,
and-- and this is key, too--

1044
00:51:18,290 --> 00:51:22,310
and Zoom has implemented
that concept correctly,

1045
00:51:22,310 --> 00:51:24,920
then, yes, maybe Zoom
is secure in the sense

1046
00:51:24,920 --> 00:51:27,470
that your video conversation
with someone else

1047
00:51:27,470 --> 00:51:29,960
is in fact private between you and them.

1048
00:51:29,960 --> 00:51:34,370
With that said, if you're in a
coffee shop or in a library, at least

1049
00:51:34,370 --> 00:51:37,580
in healthier times, and someone's
looking over or listening

1050
00:51:37,580 --> 00:51:41,080
in on your conversation, arguably
even that technology is not secure.

1051
00:51:41,080 --> 00:51:42,830
You can imagine there
being other threats.

1052
00:51:42,830 --> 00:51:47,570
Maybe you have accidentally been
vulnerable to a virus, some kind

1053
00:51:47,570 --> 00:51:49,067
of threat on your own computer.

1054
00:51:49,067 --> 00:51:50,900
And even though, yes,
your data is encrypted

1055
00:51:50,900 --> 00:51:53,480
between you and that
other person, that doesn't

1056
00:51:53,480 --> 00:51:56,420
mean there's not malicious software
running on your own personal Mac

1057
00:51:56,420 --> 00:51:59,630
or PC or the other person's,
recording everything

1058
00:51:59,630 --> 00:52:02,750
you say and uploading it to
some third-party adversary.

1059
00:52:02,750 --> 00:52:06,950
So there, too, whenever you ask or
answer questions about security,

1060
00:52:06,950 --> 00:52:09,800
take into account those
kinds of qualifications,

1061
00:52:09,800 --> 00:52:14,383
those conditionals, because
security should never

1062
00:52:14,383 --> 00:52:15,800
be discussed, really, in a vacuum.

1063
00:52:15,800 --> 00:52:19,550
So those of you who said no, I think we
could come up with even more reasons.

1064
00:52:19,550 --> 00:52:23,000
But at least let me dispel just a few
because I do think some of the flak

1065
00:52:23,000 --> 00:52:26,300
Zoom took was overstated because
those criticizing didn't really

1066
00:52:26,300 --> 00:52:29,860
understand some of the issues that
were being touted in the media.

1067
00:52:29,860 --> 00:52:36,050
So for instance, all of you today, to
log into this meeting, for instance,

1068
00:52:36,050 --> 00:52:38,810
followed a URL, most likely,
that you had been emailed

1069
00:52:38,810 --> 00:52:40,160
or that you saw on your screen.

1070
00:52:40,160 --> 00:52:44,630
And that URL probably looked a little
something like this-- https://,

1071
00:52:44,630 --> 00:52:48,620
which is good, zoom.us or something
like that, followed by a number,

1072
00:52:48,620 --> 00:52:49,700
the meeting ID--

1073
00:52:49,700 --> 00:52:52,250
for instance, 5551112222.

1074
00:52:52,250 --> 00:52:55,560
But it was a different
number for today's meeting.

1075
00:52:55,560 --> 00:52:58,970
So if you received this URL
after registering, is it secure?

1076
00:52:58,970 --> 00:53:02,870
Well, even though all of you here
right now have presumably registered,

1077
00:53:02,870 --> 00:53:05,750
technically there was
nothing stopping any of you

1078
00:53:05,750 --> 00:53:10,820
from texting or emailing
or DMing this same URL

1079
00:53:10,820 --> 00:53:12,290
to anyone else on the internet.

1080
00:53:12,290 --> 00:53:14,790
And they could therefore join,
perhaps, without registering.

1081
00:53:14,790 --> 00:53:17,720
So maybe that's a threat,
though, Zoom typically sends you

1082
00:53:17,720 --> 00:53:21,770
not a URL that's as simple as this when
you register, but a longer one, indeed.

1083
00:53:21,770 --> 00:53:24,020
And there's another detail
that some URLs have,

1084
00:53:24,020 --> 00:53:25,880
too, which might look like this--

1085
00:53:25,880 --> 00:53:29,058
a question mark at the
end, and pwd for password,

1086
00:53:29,058 --> 00:53:30,350
and then some kind of password.

1087
00:53:30,350 --> 00:53:33,290
And indeed, the URLs you clicked
today looked a little more like that,

1088
00:53:33,290 --> 00:53:37,130
still different because they
were special registration URLs.

1089
00:53:37,130 --> 00:53:40,670
But here, if your URL has
this password, now you

1090
00:53:40,670 --> 00:53:43,280
need to know both the
meeting ID and the password

1091
00:53:43,280 --> 00:53:45,555
in order to join that
particular Zoom meeting.

1092
00:53:45,555 --> 00:53:48,680
And if you're not running big classes,
like we are today with this meeting,

1093
00:53:48,680 --> 00:53:51,980
but rather you're having one-on-one
or smaller scale meetings,

1094
00:53:51,980 --> 00:53:56,480
typically you are receiving or
generating a URL that looks like this,

1095
00:53:56,480 --> 00:53:59,570
or better yet, that looks
like this, so that it

1096
00:53:59,570 --> 00:54:02,660
doesn't suffice for an adversary
to just guess the meeting ID.

1097
00:54:02,660 --> 00:54:04,670
And that's what was happening early on.

1098
00:54:04,670 --> 00:54:07,520
Zoom typically did not
require that people

1099
00:54:07,520 --> 00:54:10,820
choose passwords for their meetings,
which meant the only thing between you

1100
00:54:10,820 --> 00:54:14,090
and some adversary Zoombombing
you, so to speak, hacking

1101
00:54:14,090 --> 00:54:17,130
into your meeting, which they
just had to guess the meeting ID.

1102
00:54:17,130 --> 00:54:19,580
And we've seen already it
took me, what, like 1 minute,

1103
00:54:19,580 --> 00:54:22,310
30 seconds to write
a Python program that

1104
00:54:22,310 --> 00:54:26,780
just generated all possible numbers
of length four or eight or whatever.

1105
00:54:26,780 --> 00:54:29,570
So people with too much
free time are writing

1106
00:54:29,570 --> 00:54:32,330
code that just tries all possible URLs.

1107
00:54:32,330 --> 00:54:35,240
And so if you've ever been
Zoombombed, maybe that's

1108
00:54:35,240 --> 00:54:38,120
because someone shared the URL
with someone they shouldn't have.

1109
00:54:38,120 --> 00:54:42,140
Or maybe someone with a bit of
programming experience or just luck

1110
00:54:42,140 --> 00:54:43,880
guessed your meeting ID.

1111
00:54:43,880 --> 00:54:47,330
So this was a feature in
the sense that, honestly,

1112
00:54:47,330 --> 00:54:50,270
having to type in a meeting ID
and a password is just annoying.

1113
00:54:50,270 --> 00:54:52,830
It starts to hurt the
usability of the system.

1114
00:54:52,830 --> 00:54:55,070
And a lot of people in
the corporate world,

1115
00:54:55,070 --> 00:54:58,130
they're going to choose another
product if another product is easier

1116
00:54:58,130 --> 00:54:59,870
to start the video conference with.

1117
00:54:59,870 --> 00:55:02,300
So arguably, it was a conscious
decision on Zoom's part.

1118
00:55:02,300 --> 00:55:04,092
Now universities and
companies have started

1119
00:55:04,092 --> 00:55:07,175
requiring this or another feature
called a waiting room, which some of you

1120
00:55:07,175 --> 00:55:08,510
might have experienced today.

1121
00:55:08,510 --> 00:55:12,680
But that just, again, raises the
bar to someone attacking the system.

1122
00:55:12,680 --> 00:55:14,210
So is Zoom secure?

1123
00:55:14,210 --> 00:55:15,440
Yes and no.

1124
00:55:15,440 --> 00:55:17,660
It really should be
considered not in a vacuum,

1125
00:55:17,660 --> 00:55:21,110
but in the context of what kinds
of threats are you worried about

1126
00:55:21,110 --> 00:55:25,400
and what kinds of defenses
are you willing to put up?

1127
00:55:25,400 --> 00:55:31,040
So just like in the real world, you
might have your own home or apartment

1128
00:55:31,040 --> 00:55:36,840
or the like, on which you might have
locks and bolts and bars on the window.

1129
00:55:36,840 --> 00:55:39,240
At some point, if it takes
you five minutes to unlock

1130
00:55:39,240 --> 00:55:41,940
every lock on your door
just to get into your home,

1131
00:55:41,940 --> 00:55:44,160
it might be much more
secure, but you're probably

1132
00:55:44,160 --> 00:55:47,280
not going to enjoy going home
because it takes that long to get in.

1133
00:55:47,280 --> 00:55:50,310
And you might put bars on the window
to keep that person physically out,

1134
00:55:50,310 --> 00:55:52,380
but it's not going to
look particularly nice.

1135
00:55:52,380 --> 00:55:54,797
And there's nothing stopping
them from going one floor up.

1136
00:55:54,797 --> 00:55:56,580
So there, too, there's this trade-off.

1137
00:55:56,580 --> 00:55:59,130
And so among the takeaways,
we hope, from today, are

1138
00:55:59,130 --> 00:56:01,260
one, just better thought
processes when it

1139
00:56:01,260 --> 00:56:04,530
comes to what does it mean for
your phone or your computer

1140
00:56:04,530 --> 00:56:06,573
or your homes for that
matter to be secure,

1141
00:56:06,573 --> 00:56:09,240
and to recognize that there's
always going to be some trade-off.

1142
00:56:09,240 --> 00:56:12,460
And we would encourage you, ultimately,
to ask these kinds of questions.

1143
00:56:12,460 --> 00:56:16,210
If any company, if any app, if any
website just says on their website,

1144
00:56:16,210 --> 00:56:18,690
"we are secure," that's nonsense.

1145
00:56:18,690 --> 00:56:22,410
That means nothing in and of itself
until you start asking questions, like,

1146
00:56:22,410 --> 00:56:25,890
what are you secure against, and how?

1147
00:56:25,890 --> 00:56:27,760
Well, thank you so much
for joining us here.

1148
00:56:27,760 --> 00:56:28,890
Let's officially wrap here.

1149
00:56:28,890 --> 00:56:32,250
But folks are welcome to stick
around for some more time

1150
00:56:32,250 --> 00:56:34,720
if you'd like to ask
questions in the group.

1151
00:56:34,720 --> 00:56:37,500
But if you have to take off,
please feel free to head out.

1152
00:56:37,500 --> 00:56:39,650
[MUSIC PLAYING]

1153
00:56:39,650 --> 00:57:38,000