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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.

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There's other threats.

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In fact, anyone who's
taken CS50 or CS50x or even

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just the first few weeks of it,
learning a little bit of C or Python,

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both of which are common
programming languages, anyone

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who knows a little bit about
programming can certainly

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write software that simulates what
that robot was physically doing.

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And the thing about software is as soon
as you don't have any moving parts,

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you can do things much, much
faster because it's all electronic.

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It's not at all mechanical.

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And so in this case, what if
I were to steal your phone off

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of you, for instance, write
some software on my Mac or PC,

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and then plug my Mac
or PC into your phone

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with, again, a USB cable
or a lightning connector,

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such that I could write code that tries
all possible passcodes again and again?

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For instance, suppose
that your phone is using--

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and this is not an uncommon default
on iPhones or on Android phones,

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at least in the past--

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four digits.

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Suppose that you're
required to choose minimally

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a passcode or password, synonymous
here, that are four digits long.

00:13:30.520 --> 00:13:33.010
And we're talking decimal
digits, so 0 through 9.

00:13:33.010 --> 00:13:35.350
So 0, 1, 2, 3, 4, 5,
6, 7, 8, 9, you need

00:13:35.350 --> 00:13:38.170
to choose four of those
digits in some pattern.

00:13:38.170 --> 00:13:44.230
Well, how many possible passcodes
are there that are four digits long?

00:13:44.230 --> 00:13:48.700
If your passcode is 4 digits long, you
can begin to think about the security

00:13:48.700 --> 00:13:52.900
of your passcode in terms of, well,
how long would it take an adversary

00:13:52.900 --> 00:13:58.210
to brute force their way to my
actual password starting at 0000,

00:13:58.210 --> 00:14:01.135
going all the way up
to, for instance, 9999.

00:14:01.135 --> 00:14:03.010
Well, let me go ahead
and open up the screen.

00:14:03.010 --> 00:14:07.330
If you pull up that same URL from
before, you'll see in just a moment

00:14:07.330 --> 00:14:12.070
a poll that'll ask you this
very same question, that being,

00:14:12.070 --> 00:14:15.338
how many 4-digit passcodes are possible?

00:14:15.338 --> 00:14:17.380
In just a moment, you'll
see this on your screen.

00:14:17.380 --> 00:14:19.750
Let me go ahead and full
screen it on my end as well.

00:14:19.750 --> 00:14:22.600
Go again to the URL that's
atop my screen here,

00:14:22.600 --> 00:14:26.770
if you missed the URL earlier
or happened to close the tab.

00:14:26.770 --> 00:14:31.180
How many 4-digit passcodes are possible?

00:14:31.180 --> 00:14:33.910
How many 4-digit passcodes are possible?

00:14:33.910 --> 00:14:40.180
Among the answers here are 4 or
40 or 9,999 or maybe 10,000--

00:14:40.180 --> 00:14:42.940
or quite fine, too, you're unsure.

00:14:42.940 --> 00:14:50.170
Go ahead and buzz in with one of
those responses, if you could.

00:14:50.170 --> 00:14:53.140
All right, looks like we have got
a few hundred responses thus far.

00:14:53.140 --> 00:14:56.520
We'll give you a few
more seconds to buzz in.

00:14:56.520 --> 00:14:59.160
And let me go ahead and begin
to reveal the results here.

00:14:59.160 --> 00:15:03.645
So it looks like quite
a few of you, 60-plus%

00:15:03.645 --> 00:15:05.520
think it's 10,000 possibilities.

00:15:05.520 --> 00:15:08.730
27% of you think it's
9,999 possibilities.

00:15:08.730 --> 00:15:10.590
And then a few others
think it's 40 or four.

00:15:10.590 --> 00:15:12.210
And a bunch of you are unsure.

00:15:12.210 --> 00:15:14.130
So let's consider, then,
how we would answer

00:15:14.130 --> 00:15:17.670
this question so that we have a mental
model for answering this on our own.

00:15:17.670 --> 00:15:20.950
Let me go ahead and propose
that to answer this question,

00:15:20.950 --> 00:15:22.770
we just do some very simple arithmetic.

00:15:22.770 --> 00:15:24.600
It doesn't need to get very complicated.

00:15:24.600 --> 00:15:28.090
But the math could be thought
of in the following way.

00:15:28.090 --> 00:15:31.980
If we've got a 4-digit passcode,
that's four digits, each of which

00:15:31.980 --> 00:15:33.420
can be zero through nine.

00:15:33.420 --> 00:15:34.770
And there's 10 total digits.

00:15:34.770 --> 00:15:37.680
Therefore zero through 9.

00:15:37.680 --> 00:15:42.490
Eight nine so 10 possible values
for each of those four digits.

00:15:42.490 --> 00:15:44.790
So if that's the case,
I think it's fair to say

00:15:44.790 --> 00:15:48.480
that there's 10 possibilities for the
first digit times 10 possibilities

00:15:48.480 --> 00:15:51.507
for the second times 10 times 10.

00:15:51.507 --> 00:15:53.340
And of course, if you
multiply this all out,

00:15:53.340 --> 00:15:56.680
the answer was indeed
10,000 possibilities.

00:15:56.680 --> 00:15:59.370
So if you have an iPhone or
an Android phone right now

00:15:59.370 --> 00:16:03.060
and you've got a 4-digit passcode
that you think no one knows,

00:16:03.060 --> 00:16:04.800
that may very well be the case.

00:16:04.800 --> 00:16:07.200
But you should worry
about or consider, well,

00:16:07.200 --> 00:16:10.740
what happens if a friend with a fancy
robot connects your phone to that

00:16:10.740 --> 00:16:18.180
and just tries all possible values
from 0000 to 9999, or smarter still,

00:16:18.180 --> 00:16:21.120
connects your phone via
cable to their laptop,

00:16:21.120 --> 00:16:24.690
writes software to generate
all of those possibilities?

00:16:24.690 --> 00:16:28.740
Well, a little worrisomely, it's
not all that hard to do the latter

00:16:28.740 --> 00:16:30.210
and to actually write code.

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

00:16:33.450 --> 00:16:36.540
and open up a program
that's going to let me write

00:16:36.540 --> 00:16:39.150
some code in a file called crack.py.

00:16:39.150 --> 00:16:41.230
So "crack" is a term
of art in programming,

00:16:41.230 --> 00:16:44.790
which means to brute force your
way into a password somehow,

00:16:44.790 --> 00:16:47.507
so to figure out what
it is algorithmically.

00:16:47.507 --> 00:16:50.340
Those of you, particularly parents
and family members who have never

00:16:50.340 --> 00:16:52.170
seen any of this before, totally fine.

00:16:52.170 --> 00:16:53.580
That's new to you.

00:16:53.580 --> 00:16:56.760
Your sons and daughters
and others here in the room

00:16:56.760 --> 00:16:58.440
have seen little bit of this code.

00:16:58.440 --> 00:17:01.080
But we'll keep it short, which
is to say that it actually

00:17:01.080 --> 00:17:04.680
doesn't take all that much
effort to write code that brute

00:17:04.680 --> 00:17:06.496
forces an attack on your own phone.

00:17:06.496 --> 00:17:09.329
And the code I'm going to write
here is in a language called Python,

00:17:09.329 --> 00:17:11.079
which is quite popular these days.

00:17:11.079 --> 00:17:15.450
And I'm going to say a command like
this, from string import digits, which

00:17:15.450 --> 00:17:18.520
is just a clever way in Python,
this programming language,

00:17:18.520 --> 00:17:22.290
just give me access to all the possible
digits in decimal, 0 through 9.

00:17:22.290 --> 00:17:26.430
And then I'm going to import, so to
speak, from a library, some software

00:17:26.430 --> 00:17:29.940
that some other smart people
wrote, something called product.

00:17:29.940 --> 00:17:32.010
So it turns out, in a
programming language,

00:17:32.010 --> 00:17:34.650
you have lots of functions
or functionality.

00:17:34.650 --> 00:17:38.110
Much like in the world of math, you have
functions, like, addition, subtraction,

00:17:38.110 --> 00:17:39.330
multiplication, and division.

00:17:39.330 --> 00:17:42.510
In the world of programming, you
have all of those capabilities,

00:17:42.510 --> 00:17:43.500
but many more.

00:17:43.500 --> 00:17:45.900
And so one of the functions
I'm importing here

00:17:45.900 --> 00:17:48.090
is this notion of a product,
which really just means

00:17:48.090 --> 00:17:52.178
a permutation of all possible digits.

00:17:52.178 --> 00:17:54.720
And now I'm going to use what's
called a loop in programming.

00:17:54.720 --> 00:17:57.803
A loop in a program is just something
that does something again and again.

00:17:57.803 --> 00:18:00.270
And I'm going to go ahead
and say this, for passcode

00:18:00.270 --> 00:18:06.660
in, the product of all of those digits,
and repeat the digits four times total,

00:18:06.660 --> 00:18:09.810
go ahead and print out each passcode.

00:18:09.810 --> 00:18:13.440
Let me go ahead and print it out
using somewhat cryptic syntax.

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.

00:18:17.310 --> 00:18:20.140
Parents and family members, don't
worry for now what that means.

00:18:20.140 --> 00:18:23.370
CS50 and CS50x students,
this is just a clever way

00:18:23.370 --> 00:18:26.010
with a couple of lines
of code to iterate over

00:18:26.010 --> 00:18:30.390
all of the digits 0 through 9,
combine them four at a time,

00:18:30.390 --> 00:18:35.200
and print out all possible
permutations of those four digits.

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

00:18:38.430 --> 00:18:42.780
a command called python on
crack.py and hit Enter--

00:18:42.780 --> 00:18:43.785
boom.

00:18:43.785 --> 00:18:45.090
That was so fast.

00:18:45.090 --> 00:18:46.410
In fact, let me do it again.

00:18:46.410 --> 00:18:49.590
Let me clear my screen and
rerun this crack.py program--

00:18:49.590 --> 00:18:50.610
boom.

00:18:50.610 --> 00:18:53.790
That's how fast a computer,
my little Mac here,

00:18:53.790 --> 00:18:59.040
can try all possible codes
between 0000 and 9999.

00:18:59.040 --> 00:19:01.920
And it's so fast because it did
them all in the blink of an eye.

00:19:01.920 --> 00:19:04.920
So if you're thinking that your 4-digit
passcode is keeping you somewhat

00:19:04.920 --> 00:19:09.630
secure, it probably really isn't because
it wouldn't take that much effort

00:19:09.630 --> 00:19:12.360
for maybe someone in your
household to write code like this,

00:19:12.360 --> 00:19:15.402
connect to your phone secretly at
night when you're not paying attention,

00:19:15.402 --> 00:19:18.490
and figure out, potentially,
what your code actually is.

00:19:18.490 --> 00:19:21.535
So what would be better
than using just digits?

00:19:21.535 --> 00:19:22.410
What would be better?

00:19:22.410 --> 00:19:25.118
Well, why don't we use letters of
the alphabet, English alphabet,

00:19:25.118 --> 00:19:26.310
for today's purposes?

00:19:26.310 --> 00:19:31.110
And in the English alphabet, we have
more letters than we have numbers.

00:19:31.110 --> 00:19:32.875
So how might we think about this?

00:19:32.875 --> 00:19:34.500
Let's go ahead and ask a question here.

00:19:34.500 --> 00:19:36.960
If you change your
phone after today to use

00:19:36.960 --> 00:19:43.810
four letters of the English alphabet
instead of using numbers alone,

00:19:43.810 --> 00:19:45.940
how many possibilities are there then?

00:19:45.940 --> 00:19:48.910
Well, let me go ahead and open up
a different poll question here,

00:19:48.910 --> 00:19:54.420
which asks this time, how many
4-letter passcodes are possible?

00:19:54.420 --> 00:19:56.710
And we'll see what folks
think and answer to this,

00:19:56.710 --> 00:19:58.300
as the answers begin to come in.

00:20:00.880 --> 00:20:02.805
To be fair, I have not
qualified one thing.

00:20:02.805 --> 00:20:04.930
So you might have to be
making certain assumptions.

00:20:04.930 --> 00:20:07.930
There are indeed 26 letters
of the English alphabet.

00:20:07.930 --> 00:20:10.720
However, there's
uppercase and lowercase.

00:20:10.720 --> 00:20:13.300
So if you allow the user
to type in something case

00:20:13.300 --> 00:20:16.010
sensitively, so to speak,
where case matters,

00:20:16.010 --> 00:20:19.660
it's not 26 possibilities for
each of those four characters.

00:20:19.660 --> 00:20:22.130
It's instead 52 possibilities.

00:20:22.130 --> 00:20:24.940
So it looks like an
overwhelming number of you, 78%

00:20:24.940 --> 00:20:27.790
think there's some seven
million possibilities when

00:20:27.790 --> 00:20:29.590
using 4-letter passcodes.

00:20:29.590 --> 00:20:33.890
About 11% of you think that
52,000 are all of the passcodes.

00:20:33.890 --> 00:20:35.570
So let's go ahead and do the quick math.

00:20:35.570 --> 00:20:38.320
Again, it doesn't need to be
particularly sophisticated, the math.

00:20:38.320 --> 00:20:41.860
Let me go ahead and open up
this time, similar approach

00:20:41.860 --> 00:20:45.082
to this problem, whereby if we
have four letters of the alphabet,

00:20:45.082 --> 00:20:47.290
and let's assume case
sensitivity, which, to be fair,

00:20:47.290 --> 00:20:49.390
you might not have
assumed, well, then I think

00:20:49.390 --> 00:20:53.140
we have 52 possibilities
times 52 times 52 times

00:20:53.140 --> 00:20:57.970
52 for each of the four
letters in your passcode.

00:20:57.970 --> 00:20:59.860
And if you multiply that out-- boom--

00:20:59.860 --> 00:21:03.740
you indeed get seven
million plus possibilities.

00:21:03.740 --> 00:21:05.830
So consider the takeaway here.

00:21:05.830 --> 00:21:10.720
If you are currently using a passcode
that's four digits, purely numeric,

00:21:10.720 --> 00:21:14.980
you have only 10,000 digits between
you and some adversary hacking

00:21:14.980 --> 00:21:16.510
into your phone potentially.

00:21:16.510 --> 00:21:20.530
If you change your 4-digit
passcode to be a 4-letter passcode,

00:21:20.530 --> 00:21:23.980
then you've got seven
million possible passcodes

00:21:23.980 --> 00:21:25.420
between you and the adversary.

00:21:25.420 --> 00:21:26.660
Now, why is this better?

00:21:26.660 --> 00:21:29.710
Well, again, whether they're
using a robot or using code,

00:21:29.710 --> 00:21:32.912
it's just going to take them more
time to hack into your device.

00:21:32.912 --> 00:21:34.870
And again, at that point,
if it's going to take

00:21:34.870 --> 00:21:36.703
them that much time,
that much effort, maybe

00:21:36.703 --> 00:21:41.080
even that much money to hack into your
phone, you, relative to other people

00:21:41.080 --> 00:21:43.720
might indeed be more secure
because it's probably

00:21:43.720 --> 00:21:46.990
going to be easier for that adversary
to go steal someone else's phone

00:21:46.990 --> 00:21:49.000
and try to get into that one instead.

00:21:49.000 --> 00:21:51.820
Well, let's consider what
this does in actual code.

00:21:51.820 --> 00:21:54.970
Let me go back to my Mac here.

00:21:54.970 --> 00:21:58.000
And let me go ahead and open
up that same file as before.

00:21:58.000 --> 00:22:00.500
And let me go ahead and
change something as follows.

00:22:00.500 --> 00:22:04.630
Instead of using just digits, let me use
what I'm going to call ASCII letters.

00:22:04.630 --> 00:22:07.480
Families who are not
familiar with CS, ASCII

00:22:07.480 --> 00:22:11.080
just refers to essentially all of
the printable letters of the alphabet

00:22:11.080 --> 00:22:15.430
that you would typically see in English,
so A through Z, capital and lowercase

00:22:15.430 --> 00:22:15.970
here.

00:22:15.970 --> 00:22:18.345
And I'm going to go ahead and
change my mention of digits

00:22:18.345 --> 00:22:20.300
here to be ASCII letters as well.

00:22:20.300 --> 00:22:22.390
So again, the program
is almost identical.

00:22:22.390 --> 00:22:27.010
But it's going to use all 52 uppercase
and lowercase English letters instead

00:22:27.010 --> 00:22:28.930
of all 10 digits.

00:22:28.930 --> 00:22:30.350
Let me save this file.

00:22:30.350 --> 00:22:33.130
Let me rerun python of crack.py.

00:22:33.130 --> 00:22:36.910
And this time I actually have a
moment to walk over to the screen

00:22:36.910 --> 00:22:40.810
and point out now that we're just
now through the lower case zs.

00:22:40.810 --> 00:22:43.000
Now we're going through
all the possible passcodes

00:22:43.000 --> 00:22:44.530
that start with capital letters.

00:22:44.530 --> 00:22:46.000
It's still pretty fast.

00:22:46.000 --> 00:22:48.940
This is maybe, what,
10 seconds later done?

00:22:48.940 --> 00:22:52.690
We went from AAAA to ZZZZ.

00:22:52.690 --> 00:22:54.040
So we've raised the bar.

00:22:54.040 --> 00:22:58.330
And again, the security of our
phone in this case is arguably more.

00:22:58.330 --> 00:23:00.190
It's higher because
now it's going to take

00:23:00.190 --> 00:23:04.870
the adversary more time or more effort
to actually hack into our device.

00:23:04.870 --> 00:23:07.120
Well, let's consider, perhaps,
another question, then.

00:23:07.120 --> 00:23:11.410
What if we generalize it
further to be characters?

00:23:11.410 --> 00:23:13.277
And those of you among
families, perhaps,

00:23:13.277 --> 00:23:15.860
might not know the distinction
between characters and letters.

00:23:15.860 --> 00:23:17.830
So let me open this
up to the floor here.

00:23:17.830 --> 00:23:20.140
When you register for
a website these days,

00:23:20.140 --> 00:23:22.750
it's somewhat annoying because
those websites typically

00:23:22.750 --> 00:23:25.840
force you to choose a good password.

00:23:25.840 --> 00:23:28.990
And what do they typically
mean by good password?

00:23:28.990 --> 00:23:33.130
What does your password these days often
have to contain before the website even

00:23:33.130 --> 00:23:35.060
lets you proceed?

00:23:35.060 --> 00:23:36.580
Any thoughts?

00:23:36.580 --> 00:23:37.240
And let's see.

00:23:37.240 --> 00:23:38.240
Brian, who do we have?

00:23:38.240 --> 00:23:39.492
How about Dax?

00:23:39.492 --> 00:23:40.450
What are your thoughts?

00:23:40.450 --> 00:23:44.245
DAX: Eight characters at the very
least, number, and a capital.

00:23:44.245 --> 00:23:46.370
DAVID J. MALAN: So at least
a number and character.

00:23:46.370 --> 00:23:47.260
So combine the two.

00:23:47.260 --> 00:23:47.990
I like that.

00:23:47.990 --> 00:23:53.290
So instead of 26 or 52 or 10,
we instead have, maybe, 62

00:23:53.290 --> 00:23:54.940
if we combine letters and numbers.

00:23:54.940 --> 00:23:56.910
Other thoughts on what
websites typically--

00:23:56.910 --> 00:23:57.910
DAX: Special characters.

00:23:57.910 --> 00:23:59.327
DAVID J. MALAN: --force you to do?

00:23:59.327 --> 00:24:02.280
DAX: Special characters--
asterisk, hashtag, dollar sign.

00:24:02.280 --> 00:24:05.413
DAVID J. MALAN: OK, so special
characters or punctuation characters.

00:24:05.413 --> 00:24:06.580
So maybe it's a hash symbol.

00:24:06.580 --> 00:24:09.698
Maybe it's an exclamation point,
a parenthesis, a comma, a period,

00:24:09.698 --> 00:24:11.365
something else-- yeah, so these symbols.

00:24:11.365 --> 00:24:13.870
And frankly, I get as
annoyed as you probably

00:24:13.870 --> 00:24:16.755
do when these websites
annoy you and say, no,

00:24:16.755 --> 00:24:18.130
that you can't use that password.

00:24:18.130 --> 00:24:19.570
No, you can't use that password.

00:24:19.570 --> 00:24:21.945
You need to choose something
that's much harder to guess.

00:24:21.945 --> 00:24:26.240
But indeed, if we add punctuation to
the mix, I think we can do even better.

00:24:26.240 --> 00:24:29.922
In fact, a character, therefore,
is any type of character.

00:24:29.922 --> 00:24:30.880
Maybe it's punctuation.

00:24:30.880 --> 00:24:31.713
Maybe it's a letter.

00:24:31.713 --> 00:24:33.980
Maybe it's a digit,
unlike just letters alone.

00:24:33.980 --> 00:24:36.040
So if we have four
characters, it turns out

00:24:36.040 --> 00:24:39.670
that typically, at least in ASCII, the
system that CS50 students will know,

00:24:39.670 --> 00:24:44.050
computers typically use, there's
94 possibilities for each symbol

00:24:44.050 --> 00:24:47.590
because you've got 10
digits, zero through nine.

00:24:47.590 --> 00:24:51.340
You've got 26 lowercase letters,
26 uppercase letters-- and then

00:24:51.340 --> 00:24:55.960
if you count them up on an English
keyboard, 32 characters more that

00:24:55.960 --> 00:24:58.690
represent punctuation,
like, hashes and exclamation

00:24:58.690 --> 00:25:00.010
points and commas and periods.

00:25:00.010 --> 00:25:03.080
So if you have 94 possibilities
for each of those symbols,

00:25:03.080 --> 00:25:08.840
it turns out that you then have a
total of 78 million possible passcodes.

00:25:08.840 --> 00:25:10.280
And that's pretty good.

00:25:10.280 --> 00:25:12.890
Now we're really raising
the bar to the adversary

00:25:12.890 --> 00:25:18.140
because now they have to waste even more
time trying to hack into your passcode.

00:25:18.140 --> 00:25:21.170
And in fact, let me go ahead and
simulate that with some actual code.

00:25:21.170 --> 00:25:23.990
Let me go ahead and open up
my same program as before.

00:25:23.990 --> 00:25:27.290
And this time let me go ahead and
import not just ASCII letters,

00:25:27.290 --> 00:25:30.560
but also digits, and also
literally, punctuation.

00:25:30.560 --> 00:25:33.200
The code I'm writing in this
language called Python literally

00:25:33.200 --> 00:25:35.600
gives me access to all
printable punctuation

00:25:35.600 --> 00:25:38.240
by just importing it with
this first line of code.

00:25:38.240 --> 00:25:41.390
And I just need to change
one line of code down here.

00:25:41.390 --> 00:25:47.930
I need to actually say ASCII letters
plus digits plus punctuation.

00:25:47.930 --> 00:25:52.160
So this is Python shorthand
notation for joining multiple lists.

00:25:52.160 --> 00:25:55.580
Those CS50 students among you will know
that you can join two lists, perhaps,

00:25:55.580 --> 00:25:57.710
in this way, using what
looks like concatenation.

00:25:57.710 --> 00:25:59.940
But with lists, it
combines them all together.

00:25:59.940 --> 00:26:01.760
But I'm still going to
do of length 4 here.

00:26:01.760 --> 00:26:03.620
Now let me go ahead
and save this program

00:26:03.620 --> 00:26:05.990
and rerun it as python of crack.py.

00:26:05.990 --> 00:26:10.550
And now I can frankly take my
time walking over to the screen

00:26:10.550 --> 00:26:14.630
because now what you're seeing on
the screen is four possible symbols.

00:26:14.630 --> 00:26:18.230
But it's including 32 possible
punctuation symbols, which

00:26:18.230 --> 00:26:20.630
means this list is much longer, right?

00:26:20.630 --> 00:26:22.700
At this point in the
story, we were already

00:26:22.700 --> 00:26:26.280
through all of the lowercase
letters up through Z a moment ago.

00:26:26.280 --> 00:26:32.900
Now we're only at the Ms,
Ns, Os, Ps, which is to say,

00:26:32.900 --> 00:26:35.480
that if my Mac weren't just
printing this on the screen,

00:26:35.480 --> 00:26:38.870
but were instead connected to your
phone that I stole and somehow

00:26:38.870 --> 00:26:41.990
sending all of these possible
passcodes into your phone,

00:26:41.990 --> 00:26:44.930
it would be taking this
much time to actually solve.

00:26:44.930 --> 00:26:47.630
Now, to be fair, we're
almost at the lowercase zs.

00:26:47.630 --> 00:26:52.400
So if we stall for a minute or two
longer, this program, too, will finish.

00:26:52.400 --> 00:26:57.420
So even 78 million possibilities
is not all that impressive.

00:26:57.420 --> 00:27:00.810
And so I daresay that we should
do even better than this.

00:27:00.810 --> 00:27:05.420
So what might be better than
four characters for a password?

00:27:05.420 --> 00:27:06.980
Any thoughts or volunteers?

00:27:06.980 --> 00:27:10.790
What would be a better password
than four characters, where,

00:27:10.790 --> 00:27:16.530
again, each character is a letter,
a number, or a punctuation symbol?

00:27:16.530 --> 00:27:17.530
The list is pretty good.

00:27:17.530 --> 00:27:19.238
But I think we can do
better because even

00:27:19.238 --> 00:27:22.290
this will be done in under a minute.

00:27:22.290 --> 00:27:23.850
Yeah, thoughts about it, Leo?

00:27:23.850 --> 00:27:25.590
LEO: Right.

00:27:25.590 --> 00:27:28.310
Have a longer password to use,
like, at least eight characters.

00:27:28.310 --> 00:27:29.310
DAVID J. MALAN: Perfect.

00:27:29.310 --> 00:27:31.268
So have a longer password
using at least eight.

00:27:31.268 --> 00:27:33.777
And notice here, we're even
now going through the numbers.

00:27:33.777 --> 00:27:35.860
But we're almost done, it
seems, with the numbers.

00:27:35.860 --> 00:27:37.420
But now we're going through punctuation.

00:27:37.420 --> 00:27:39.837
But again, if I give this a
little more time-- and I think

00:27:39.837 --> 00:27:41.018
I was a little overzealous.

00:27:41.018 --> 00:27:42.810
Under a minute probably
isn't going to fly.

00:27:42.810 --> 00:27:45.570
But certainly, by the end of
class, that will have been done.

00:27:45.570 --> 00:27:48.660
But what if we do a little
better and use eight characters?

00:27:48.660 --> 00:27:50.970
Well, eight characters is
going to take even longer.

00:27:50.970 --> 00:27:54.403
But let's go ahead and ask you all
how much longer this might take.

00:27:54.403 --> 00:27:56.820
Let me go ahead and open up a
somewhat different question,

00:27:56.820 --> 00:27:58.300
but similar in spirit.

00:27:58.300 --> 00:28:01.300
In just a moment that will
appear on your screen.

00:28:01.300 --> 00:28:05.010
And the question here is going to be
how many 8-character passcodes are

00:28:05.010 --> 00:28:06.060
possible?

00:28:06.060 --> 00:28:08.280
And this time I'm waving my hand at it.

00:28:08.280 --> 00:28:11.310
I didn't even bother doing
the math precisely yet.

00:28:11.310 --> 00:28:13.560
But I'm proposing that
it's roughly a million,

00:28:13.560 --> 00:28:18.090
a billion, a trillion, a
quadrillion, a quintillion.

00:28:18.090 --> 00:28:20.737
Some of you are perhaps
noticing a pattern here.

00:28:20.737 --> 00:28:22.320
And you went straight for quintillion.

00:28:22.320 --> 00:28:24.790
That bar jumped up really fast.

00:28:24.790 --> 00:28:26.160
So maybe you're right.

00:28:26.160 --> 00:28:27.480
Good instincts, perhaps.

00:28:27.480 --> 00:28:29.550
It looks like we're getting equilibrium.

00:28:29.550 --> 00:28:32.190
About 60% of you think
it's 1 quintillion.

00:28:32.190 --> 00:28:34.350
25% of you think it's a quadrillion.

00:28:34.350 --> 00:28:36.600
And then fewer and fewer for the others.

00:28:36.600 --> 00:28:39.060
Well, let's take a look at
what the actual answer is.

00:28:39.060 --> 00:28:42.640
Give me just a moment to actually
do out the math here on my screen.

00:28:42.640 --> 00:28:45.120
And if we do out the
math on my screen here,

00:28:45.120 --> 00:28:47.760
we'll see, of course, that
we need to do some more math.

00:28:47.760 --> 00:28:52.620
We need to do 94 times itself
eight times instead of just four,

00:28:52.620 --> 00:28:55.350
to Leo's suggestion of using
eight possible symbols.

00:28:55.350 --> 00:28:58.020
And if you do this out, I
had to think about this.

00:28:58.020 --> 00:29:02.880
This in fact is, let's see, we've
got millions, billions, trillions,

00:29:02.880 --> 00:29:04.200
quadrillions.

00:29:04.200 --> 00:29:04.860
Gotcha.

00:29:04.860 --> 00:29:07.470
So it wasn't the biggest
option on the list.

00:29:07.470 --> 00:29:09.810
The answer is indeed quadrillion.

00:29:09.810 --> 00:29:12.330
So 6 quadrillion, if you will.

00:29:12.330 --> 00:29:15.120
But-- but-- but those
of you who are fans

00:29:15.120 --> 00:29:18.765
of having quintillion possibilities,
which is pretty, pretty

00:29:18.765 --> 00:29:21.390
secure because it's just going
to take the adversary way longer

00:29:21.390 --> 00:29:26.910
to hack into your password, well,
all it takes to go from 6 quadrillion

00:29:26.910 --> 00:29:31.210
to some number of quintillion
is just two more characters.

00:29:31.210 --> 00:29:35.070
So in fact, if Leo had proposed
not an 8-character passcode,

00:29:35.070 --> 00:29:39.300
but a 10-character passcode, we
actually would have hit quintillions.

00:29:39.300 --> 00:29:40.890
So life gets interesting.

00:29:40.890 --> 00:29:44.610
Life gets more secure, the longer
and longer and more complicated

00:29:44.610 --> 00:29:46.380
these passcodes get.

00:29:46.380 --> 00:29:49.140
All right, so by logic,
then, you should all probably

00:29:49.140 --> 00:29:51.210
have passcodes that
are not eight, not 10.

00:29:51.210 --> 00:29:53.280
Maybe they're 20 characters long.

00:29:53.280 --> 00:29:55.350
Maybe they're 100 characters long.

00:29:55.350 --> 00:29:58.920
But here we see another theme
in security, that of trade-offs.

00:29:58.920 --> 00:30:03.510
Like, the end all is probably
not to be as secure as possible,

00:30:03.510 --> 00:30:05.850
but to be as secure as
possible conditional

00:30:05.850 --> 00:30:08.020
on some other goals you might have.

00:30:08.020 --> 00:30:10.500
So let me ask this,
what's the trade-off here?

00:30:10.500 --> 00:30:15.240
In making your password longer and
longer and more and more complicated,

00:30:15.240 --> 00:30:18.270
what price do you pay as the human?

00:30:18.270 --> 00:30:19.530
What's the downside?

00:30:19.530 --> 00:30:22.350
In computer science, as in
life, there's always a catch.

00:30:22.350 --> 00:30:24.070
There's always a cost.

00:30:24.070 --> 00:30:27.840
So what's the cost when you make
your passcode more and more secure?

00:30:27.840 --> 00:30:28.620
Any thoughts?

00:30:28.620 --> 00:30:29.323
Let see.

00:30:29.323 --> 00:30:30.240
Who do we have, Brian?

00:30:30.240 --> 00:30:32.190
Over to Jenny?

00:30:32.190 --> 00:30:32.940
What do you think?

00:30:32.940 --> 00:30:36.480
JENNY: Yeah, I feel that it is
very difficult for a human being

00:30:36.480 --> 00:30:38.100
to remember such a long password.

00:30:38.100 --> 00:30:41.910
And due to that, we even store those
long passwords somewhere in the system

00:30:41.910 --> 00:30:45.267
itself so that we can use that whenever
we have to log in into the system.

00:30:45.267 --> 00:30:47.100
DAVID J. MALAN: Yeah,
there's this trade-off

00:30:47.100 --> 00:30:48.660
of just remembering the darn things.

00:30:48.660 --> 00:30:49.950
And you make a perfect point.

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

00:30:54.527 --> 00:30:57.610
good passwords, and by good passwords,
I mean, some numbers, some letters,

00:30:57.610 --> 00:31:02.430
some punctuation, but it's written on
a Post-It note on your monitor at work,

00:31:02.430 --> 00:31:06.540
or maybe it's slightly more cleverly
written in a Microsoft Word file

00:31:06.540 --> 00:31:08.910
in your hard drive, or
maybe it's in a Google Doc,

00:31:08.910 --> 00:31:11.610
or maybe it's even on a piece
of paper in your drawer--

00:31:11.610 --> 00:31:14.740
you're just exposing yourself
to other threats, of course.

00:31:14.740 --> 00:31:18.123
But here, too, is a sociological
consideration or just a policy

00:31:18.123 --> 00:31:20.790
consideration, whether you're
running a business or a university

00:31:20.790 --> 00:31:23.370
or just a household with
multiple family members.

00:31:23.370 --> 00:31:25.140
What should your own policies be?

00:31:25.140 --> 00:31:28.170
Because arguably it's not
Jenny's fault, it's not our fault

00:31:28.170 --> 00:31:31.170
if we are resorting to
writing things down on paper

00:31:31.170 --> 00:31:34.380
if our passwords are so
darn hard to remember.

00:31:34.380 --> 00:31:36.870
And moreover, I haven't even
made the suggestion yet,

00:31:36.870 --> 00:31:39.150
but if you are one of
those people in life

00:31:39.150 --> 00:31:42.510
who is using the same
password on multiple devices

00:31:42.510 --> 00:31:46.620
or on multiple websites or on
multiple apps, you are bad.

00:31:46.620 --> 00:31:48.930
Like, you are also doing something bad.

00:31:48.930 --> 00:31:49.590
Why?

00:31:49.590 --> 00:31:52.770
Because if any one of those
apps or websites is compromised

00:31:52.770 --> 00:31:55.080
and your password gets out,
whether it's "iloveyou,"

00:31:55.080 --> 00:31:57.750
quote unquote, or something
much more complicated,

00:31:57.750 --> 00:32:01.680
all an adversary has to do
now is try that same password

00:32:01.680 --> 00:32:02.910
on your other accounts.

00:32:02.910 --> 00:32:06.372
And so you're just exposing yourself
to more risk by reusing passwords.

00:32:06.372 --> 00:32:08.580
But to Jenny's point here,
my God, where does it end?

00:32:08.580 --> 00:32:12.420
Now I need a really long random
password on this website, this one,

00:32:12.420 --> 00:32:14.500
and this one, and this
app, all over the place.

00:32:14.500 --> 00:32:18.300
I mean, honestly, I as a human certainly
can't remember all of those passwords.

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

00:32:21.640 --> 00:32:24.650
than passwords for accounts like this.

00:32:24.650 --> 00:32:26.170
So there's surely a trade-off here.

00:32:26.170 --> 00:32:30.790
But again, the goal is to keep the
adversary out with some probability,

00:32:30.790 --> 00:32:33.460
not necessarily out in the absolute.

00:32:33.460 --> 00:32:39.040
So what else can we do to prevent the
adversary from hacking into our systems

00:32:39.040 --> 00:32:42.880
so that I can have a somewhat
easier, more memorable passcode,

00:32:42.880 --> 00:32:44.110
but at least keep them out?

00:32:44.110 --> 00:32:45.860
Well, here's a screenshot
of something you

00:32:45.860 --> 00:32:48.100
might have done by
accident, perhaps late

00:32:48.100 --> 00:32:51.010
at night when a little groggy,
or a little blurry-eyed,

00:32:51.010 --> 00:32:54.670
trying to type in your password
incorrectly too many times.

00:32:54.670 --> 00:32:56.980
In fact, by a show of physical
hands, how many people

00:32:56.980 --> 00:33:01.840
have locked yourself out of your phone
before by typing in the wrong password

00:33:01.840 --> 00:33:02.740
too many times?

00:33:02.740 --> 00:33:04.870
I did it, like, literally
just the other day.

00:33:04.870 --> 00:33:07.910
And so on iPhone, for instance, it
looks a little something like this.

00:33:07.910 --> 00:33:11.660
And if we zoom in, notice that
it's saying, try again in 1 minute.

00:33:11.660 --> 00:33:14.570
So you don't have to get rid
of the phone and start over.

00:33:14.570 --> 00:33:17.050
But the iPhone is telling
you to come back in a minute.

00:33:17.050 --> 00:33:19.960
And if we look at, for instance,
Android, something similar--

00:33:19.960 --> 00:33:22.300
your Android wallpaper
will differ, certainly.

00:33:22.300 --> 00:33:25.300
But down here, for instance,
it says too many attempts.

00:33:25.300 --> 00:33:26.012
Try again later.

00:33:26.012 --> 00:33:28.720
I mean, that's a little infuriating
because if I pick up my phone

00:33:28.720 --> 00:33:30.130
now, I want to get in now.

00:33:30.130 --> 00:33:31.660
Well, when the heck is later?

00:33:31.660 --> 00:33:35.600
So putting that aside,
what's the takeaway here?

00:33:35.600 --> 00:33:39.005
Why are Apple and why
are Google doing this?

00:33:39.005 --> 00:33:42.130
Because I bet all of you, if you've
ever locked yourself out of your phone,

00:33:42.130 --> 00:33:45.280
are super annoyed at that moment
in time and probably don't

00:33:45.280 --> 00:33:47.280
appreciate Apple or Google.

00:33:47.280 --> 00:33:49.030
But what's the upside
of what they've just

00:33:49.030 --> 00:33:53.350
done when they lock you out
of your phone for having

00:33:53.350 --> 00:33:56.800
guessed your password incorrectly?

00:33:56.800 --> 00:34:00.460
Why is this arguably a feature
and not a bug, a mistake?

00:34:00.460 --> 00:34:01.090
Sam?

00:34:01.090 --> 00:34:04.895
SAM: Yeah, it's used to decrease the
chances of a successful brute force

00:34:04.895 --> 00:34:05.395
attack.

00:34:05.395 --> 00:34:08.979
DAVID J. MALAN: And how does it decrease
the chance of that, would you say?

00:34:08.979 --> 00:34:15.310
SAM: Because it makes the attacker
have to commit more tries before they

00:34:15.310 --> 00:34:17.380
can successfully get into the phone.

00:34:17.380 --> 00:34:18.969
So it decreases the chances.

00:34:18.969 --> 00:34:20.090
DAVID J. MALAN: Exactly.

00:34:20.090 --> 00:34:22.840
So this is a very common
principle in security.

00:34:22.840 --> 00:34:26.590
And it was pointed out earlier,
too, just slow the adversary down.

00:34:26.590 --> 00:34:28.760
We don't have to rethink
the problem of security.

00:34:28.760 --> 00:34:31.060
We don't have to redesign
passwords necessarily.

00:34:31.060 --> 00:34:33.219
But we should make it
harder for the adversary

00:34:33.219 --> 00:34:36.909
to log in, ideally, without making
it harder for you and I to log

00:34:36.909 --> 00:34:37.960
in to our own devices.

00:34:37.960 --> 00:34:41.650
So consider the simplest
passcode that had four digits.

00:34:41.650 --> 00:34:45.010
A 4-digit passcode, there
were 10,000 possibilities.

00:34:45.010 --> 00:34:47.980
A computer, a robot could guess
all of those pretty quickly.

00:34:47.980 --> 00:34:51.639
But what if after typing in
the wrong passcode three times

00:34:51.639 --> 00:34:55.780
or maybe ten times, some small number
of times, what if the iPhone or Android

00:34:55.780 --> 00:34:59.560
phone locks you out for a minute,
just like iPhone did a moment ago?

00:34:59.560 --> 00:35:03.040
Well, that might mean, even though
there's only 10,000 possibilities,

00:35:03.040 --> 00:35:06.040
maybe it will take the
adversary 10,000 minutes

00:35:06.040 --> 00:35:10.820
to track your password because they
keep getting slowed down every time

00:35:10.820 --> 00:35:12.070
they type in an incorrect one.

00:35:12.070 --> 00:35:13.403
And maybe it's not quite 10,000.

00:35:13.403 --> 00:35:15.350
It's some factor of that.

00:35:15.350 --> 00:35:17.020
But you can slow them down in that way.

00:35:17.020 --> 00:35:21.760
Maybe you have a 10-character passcode
with 78 quadrillion possibilities.

00:35:21.760 --> 00:35:25.330
And imagine the phone just
slows you down 1 second.

00:35:25.330 --> 00:35:28.120
Maybe you can only type in
one passcode per second.

00:35:28.120 --> 00:35:29.680
That sounds pretty fast.

00:35:29.680 --> 00:35:33.730
But 78 quadrillion
seconds is crazy long.

00:35:33.730 --> 00:35:36.880
And so even that kind of
slowdown might very well

00:35:36.880 --> 00:35:39.580
be enough to keep the adversary out.

00:35:39.580 --> 00:35:43.398
And so if you don't have features like
this enabled on, really, any device,

00:35:43.398 --> 00:35:44.440
you should look for them.

00:35:44.440 --> 00:35:47.860
Nowadays, thankfully, they tend
to come pre-configured for this.

00:35:47.860 --> 00:35:49.810
But there is a downside.

00:35:49.810 --> 00:35:50.997
There is a downside.

00:35:50.997 --> 00:35:53.080
You shouldn't just turn
on these kinds of defenses

00:35:53.080 --> 00:35:56.800
blindly because what's the downside
of keeping this feature enabled

00:35:56.800 --> 00:35:59.950
or leaving it enabled--

00:35:59.950 --> 00:36:03.970
those are the same things-- or enabling
it, if it's not already enabled?

00:36:03.970 --> 00:36:06.310
What's the downside here, to be clear?

00:36:06.310 --> 00:36:10.750
Because none of our advice
today will be 100% a win.

00:36:10.750 --> 00:36:11.500
David?

00:36:11.500 --> 00:36:13.780
DAVID: Well, if you
forget your password,

00:36:13.780 --> 00:36:16.780
that means it's going to take longer
for you to access your phone again.

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,

00:36:20.140 --> 00:36:21.400
even longer to log in.

00:36:21.400 --> 00:36:25.060
And I'll admit, too, I have on multiple
occasions not locked myself out once.

00:36:25.060 --> 00:36:25.978
I then got stubborn.

00:36:25.978 --> 00:36:27.520
And I think my anger level just rose.

00:36:27.520 --> 00:36:30.640
So I started typing in more angrily,
and therefore making more mistakes.

00:36:30.640 --> 00:36:33.070
And what Apple and
Google do is they have

00:36:33.070 --> 00:36:35.380
what you might describe as
exponential backoff, which

00:36:35.380 --> 00:36:38.847
is a fancy way of saying, the first
time you get penalized one minute.

00:36:38.847 --> 00:36:40.180
Now you have to wait one minute.

00:36:40.180 --> 00:36:43.030
If you screw up again, then
you have to wait two minutes.

00:36:43.030 --> 00:36:45.023
If you screw up again,
maybe it's five minutes.

00:36:45.023 --> 00:36:45.940
Maybe it's 10 minutes.

00:36:45.940 --> 00:36:46.840
Maybe it's an hour.

00:36:46.840 --> 00:36:49.715
And I swear, at that point I wanted
to throw my phone across the room

00:36:49.715 --> 00:36:51.700
because I couldn't get
into my own device.

00:36:51.700 --> 00:36:55.840
And there you start to sacrifice,
of course, usability, right?

00:36:55.840 --> 00:37:00.190
If my device is so secure
that even I can't get into it,

00:37:00.190 --> 00:37:02.080
then is it really worth having at all?

00:37:02.080 --> 00:37:04.780
And so finding that
inflection point is part

00:37:04.780 --> 00:37:07.720
of engineering good
secure systems because you

00:37:07.720 --> 00:37:10.150
have to find that inflection
point so that your users

00:37:10.150 --> 00:37:12.190
are using good passwords and passcodes.

00:37:12.190 --> 00:37:16.300
But they're not just taping them
onto the monitor on a Post-It note

00:37:16.300 --> 00:37:19.123
or disabling them all together.

00:37:19.123 --> 00:37:21.040
All right, let me pause
here to see, are there

00:37:21.040 --> 00:37:27.310
any questions about passwords,
passcodes, brute forcing or these kinds

00:37:27.310 --> 00:37:30.550
of defenses, given that
passwords are perhaps

00:37:30.550 --> 00:37:33.520
our most common defense
against adversaries

00:37:33.520 --> 00:37:36.880
accessing hardware and software
that we don't want them to?

00:37:36.880 --> 00:37:38.485
Yeah, Dax, question?

00:37:38.485 --> 00:37:40.720
DAX: Now so there is
a definite number we

00:37:40.720 --> 00:37:43.240
can calculate that for
4-digit numbers this is

00:37:43.240 --> 00:37:46.120
the most possible number of outcomes.

00:37:46.120 --> 00:37:47.918
But what about biometrics?

00:37:47.918 --> 00:37:48.460
Fingerprints?

00:37:48.460 --> 00:37:49.845
Face scanning?

00:37:49.845 --> 00:37:51.710
DAVID J. MALAN: Yeah,
really good question.

00:37:51.710 --> 00:37:53.950
So what about biometrics,
using face scanning?

00:37:53.950 --> 00:37:58.397
Like, Apple has face ID these days,
which also annoys me sometimes

00:37:58.397 --> 00:37:59.980
if it doesn't quite get my face right.

00:37:59.980 --> 00:38:02.230
Or these days if we're
wearing masks, it's

00:38:02.230 --> 00:38:03.910
infuriating to use that kind of feature.

00:38:03.910 --> 00:38:07.935
But maybe probabilistically, there
are fewer people with exactly

00:38:07.935 --> 00:38:09.560
your facial features than someone else.

00:38:09.560 --> 00:38:12.060
And so that would be more secure
than picking some passcode.

00:38:12.060 --> 00:38:14.770
Sometimes you use
fingerprints or retinal scans

00:38:14.770 --> 00:38:17.650
or the distance between your fingers,
all of these different measures

00:38:17.650 --> 00:38:21.850
that statistically tend
to not so much uniquely

00:38:21.850 --> 00:38:25.508
identify us, but uniquely
identify us all enough.

00:38:25.508 --> 00:38:26.800
And there's threats there, too.

00:38:26.800 --> 00:38:28.508
A former colleague of
ours, for instance,

00:38:28.508 --> 00:38:31.090
had a twin brother who
because of Apple's face ID

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

00:38:34.330 --> 00:38:36.980
because as twins, they both
looked all too similar.

00:38:36.980 --> 00:38:39.580
So there's downsides
and upsides there, too.

00:38:39.580 --> 00:38:42.070
But biometrics can also
help things so that it's

00:38:42.070 --> 00:38:45.130
a factor you have on you
always and not something,

00:38:45.130 --> 00:38:48.010
for instance, that you
just only have to remember.

00:38:48.010 --> 00:38:51.520
And in fact, that's a perfect
segue to what computer scientists

00:38:51.520 --> 00:38:54.217
call two-factor authentication.

00:38:54.217 --> 00:38:56.050
In the security world,
security people would

00:38:56.050 --> 00:39:01.070
call the passwords we're using
one factor, and something

00:39:01.070 --> 00:39:03.380
like biometrics, a second factor.

00:39:03.380 --> 00:39:06.350
And indeed, two-factor authentication
means a defense mechanism

00:39:06.350 --> 00:39:09.050
against the adversaries that
doesn't rely just on something

00:39:09.050 --> 00:39:10.970
you know, like, a password.

00:39:10.970 --> 00:39:14.540
It also relies on something
typically that you have, like,

00:39:14.540 --> 00:39:18.570
a hand or fingers or
eyes or face or the like,

00:39:18.570 --> 00:39:21.980
so that even if someone
compromises your password

00:39:21.980 --> 00:39:25.490
and downloads it somewhere from a
database where you've used it before,

00:39:25.490 --> 00:39:28.490
they don't necessarily have
access to your eyes and your hands

00:39:28.490 --> 00:39:31.500
and your face and the like, unless
they have physical access to you.

00:39:31.500 --> 00:39:33.680
So it just narrows the
scope of the threats.

00:39:33.680 --> 00:39:35.900
But there's other forms of
two-factor authentication.

00:39:35.900 --> 00:39:38.718
For instance, if this sounds
familiar now, and maybe

00:39:38.718 --> 00:39:40.760
you don't even call it
two-factor authentication.

00:39:40.760 --> 00:39:43.970
It's often called
two-step authentication.

00:39:43.970 --> 00:39:47.210
By a show of physical hands, who
has one or more accounts that

00:39:47.210 --> 00:39:51.000
uses two factors instead of just one?

00:39:51.000 --> 00:39:54.350
Yeah, so here, too, it's good
to see so many hands going up.

00:39:54.350 --> 00:39:58.370
But if you do not use
two-factor authentication

00:39:58.370 --> 00:40:03.170
for things like your email account or
your bank accounts or your brokerage

00:40:03.170 --> 00:40:06.830
accounts or your health
medical accounts,

00:40:06.830 --> 00:40:09.110
you really should start
considering doing so.

00:40:09.110 --> 00:40:10.880
And what form does this typically take?

00:40:10.880 --> 00:40:12.963
Well, let me show a
screenshot here, for instance.

00:40:12.963 --> 00:40:14.930
Even if you just have
a simple Gmail account

00:40:14.930 --> 00:40:17.570
that you use for work
or for personal use,

00:40:17.570 --> 00:40:20.480
you can enable what Google calls
two-step verification, which

00:40:20.480 --> 00:40:22.360
is two-factor authentication.

00:40:22.360 --> 00:40:24.860
And what you'll be prompted for
when logging into your Gmail

00:40:24.860 --> 00:40:29.250
account if you enable this is not
only your username and your password,

00:40:29.250 --> 00:40:31.070
but also a 6-digit code.

00:40:31.070 --> 00:40:33.710
And six digits doesn't
sound terribly long.

00:40:33.710 --> 00:40:36.620
But in this case, the way these
technologies typically work

00:40:36.620 --> 00:40:42.200
is that you are sent that 6-digit code
once via email or via text message

00:40:42.200 --> 00:40:46.010
or via special app that you install
on your phone or some other device

00:40:46.010 --> 00:40:48.170
so that only you have that code.

00:40:48.170 --> 00:40:50.060
Only you have that device.

00:40:50.060 --> 00:40:51.800
And therefore, only you know that code.

00:40:51.800 --> 00:40:54.380
And better yet, these codes expire.

00:40:54.380 --> 00:40:57.770
So even if some adversary
intercepts it or sees you typing it

00:40:57.770 --> 00:41:00.560
in over your shoulder, you
can only use these codes once,

00:41:00.560 --> 00:41:02.750
which makes them even
better than passwords

00:41:02.750 --> 00:41:06.680
alone because they expire
after single time use.

00:41:06.680 --> 00:41:08.450
And so consider now, again--

00:41:08.450 --> 00:41:10.400
and I can't emphasize
this enough-- if you

00:41:10.400 --> 00:41:13.242
are of the age where you have
your own bank accounts, again,

00:41:13.242 --> 00:41:15.200
brokerage accounts,
anything medically related,

00:41:15.200 --> 00:41:17.600
anything that you find
especially important or personal,

00:41:17.600 --> 00:41:21.830
like, your own email or chat accounts,
if you're only using a password,

00:41:21.830 --> 00:41:24.920
you now as of today already
have the mathematical tools

00:41:24.920 --> 00:41:28.010
and the mental model, I
daresay, to figure out just

00:41:28.010 --> 00:41:32.780
how easily someone could compromise your
account and get into your information

00:41:32.780 --> 00:41:35.637
and take your money or read
your emails or the like.

00:41:35.637 --> 00:41:38.720
So you can improve that situation by
just coming up with a better, longer,

00:41:38.720 --> 00:41:42.410
more random password that you
remember or memorize in some way,

00:41:42.410 --> 00:41:46.820
or additionally, by enabling the
second factor so that you narrow

00:41:46.820 --> 00:41:52.710
the number of threats that are
dangerous to you as a result.

00:41:52.710 --> 00:41:55.112
So with that said, too, with
two-factor authentication,

00:41:55.112 --> 00:41:57.320
there's another thing you
can bring into play when it

00:41:57.320 --> 00:41:59.810
comes to managing all your passwords.

00:41:59.810 --> 00:42:03.230
I alluded to using Microsoft
Word before or a Post-It note.

00:42:03.230 --> 00:42:05.970
There are software
solutions to this, too.

00:42:05.970 --> 00:42:09.320
So another defense we would like to
offer up for your consideration today

00:42:09.320 --> 00:42:11.510
is what's generally
called a password manager.

00:42:11.510 --> 00:42:14.645
This is a piece of software, either
for free or that you pay for,

00:42:14.645 --> 00:42:17.300
for your phone or your
laptop or desktop, that

00:42:17.300 --> 00:42:19.160
literally manages your passwords.

00:42:19.160 --> 00:42:23.750
In its simplest form, think of it like
a spreadsheet, but that's "secure,"

00:42:23.750 --> 00:42:25.670
quote unquote, on your own computer.

00:42:25.670 --> 00:42:28.970
That is, these password managers--
and here's two popular ones.

00:42:28.970 --> 00:42:33.483
onepassword.com is one popular
tool. lastpass.com is another one.

00:42:33.483 --> 00:42:35.150
And there's others if you google around.

00:42:35.150 --> 00:42:37.970
But I would, as always, read up
on reviews or get second opinions.

00:42:37.970 --> 00:42:40.160
Don't just take at face
value what we propose.

00:42:40.160 --> 00:42:42.620
But these password managers
are programs that you

00:42:42.620 --> 00:42:45.920
type your usernames and passwords into.

00:42:45.920 --> 00:42:52.040
And then you save them all behind one
master password, one password that's

00:42:52.040 --> 00:42:54.650
really long, hopefully,
really random with lots

00:42:54.650 --> 00:42:56.210
of numbers and letters and symbols.

00:42:56.210 --> 00:43:00.710
But all you have to remember
is that one main password.

00:43:00.710 --> 00:43:04.040
And by entering that password
into your Mac or PC or phone,

00:43:04.040 --> 00:43:06.230
you then unlock all of
your other accounts.

00:43:06.230 --> 00:43:09.920
And you can then just copy and paste
your actual accounts' usernames

00:43:09.920 --> 00:43:10.725
and passwords.

00:43:10.725 --> 00:43:12.850
Or these programs also give
you keyboard shortcuts.

00:43:12.850 --> 00:43:16.430
So you hit a keyboard command,
and voila, you're automatically

00:43:16.430 --> 00:43:17.420
logged into websites.

00:43:17.420 --> 00:43:20.000
You don't have to copy/paste
or manually transcribe them.

00:43:20.000 --> 00:43:21.860
So to this day, what does this mean?

00:43:21.860 --> 00:43:24.230
For me, I use one of
these password managers.

00:43:24.230 --> 00:43:25.980
And most of my colleagues do as well.

00:43:25.980 --> 00:43:29.660
Many of us, most of us,
don't even know the passwords

00:43:29.660 --> 00:43:32.960
we use for various websites
or apps or the like.

00:43:32.960 --> 00:43:33.590
Why?

00:43:33.590 --> 00:43:35.780
Because we now trust
that the password manager

00:43:35.780 --> 00:43:39.710
can, with the click of a button,
generate a really long random password

00:43:39.710 --> 00:43:41.870
with lots of numbers,
digits, and punctuation.

00:43:41.870 --> 00:43:44.510
And then it will remember it for me.

00:43:44.510 --> 00:43:47.870
And I just have to remember
that one main password that's

00:43:47.870 --> 00:43:50.430
protecting all of those others.

00:43:50.430 --> 00:43:54.890
So that's good in that now I can
practice what I've been preaching.

00:43:54.890 --> 00:43:58.330
But there is a downside.

00:43:58.330 --> 00:44:01.420
I'm exposing myself to a
new risk or vulnerability.

00:44:01.420 --> 00:44:03.760
That is to say, what's
the trade-off here?

00:44:03.760 --> 00:44:07.360
Why should you not necessarily
just run off after today's class,

00:44:07.360 --> 00:44:11.260
download and install a password
manager, and start using it

00:44:11.260 --> 00:44:13.990
without a little bit of thought first.

00:44:13.990 --> 00:44:17.080
What's the downside, perhaps?

00:44:17.080 --> 00:44:23.580
Yeah, over to Lexlene
if I'm saying it right?

00:44:23.580 --> 00:44:30.390
LEXLENE: Yeah, if someone cracks
your password manager password,

00:44:30.390 --> 00:44:32.840
then they have access
to all your passwords.

00:44:32.840 --> 00:44:35.893
DAVID J. MALAN: Yeah, so really
depends on what the threat here is,

00:44:35.893 --> 00:44:37.310
or what you're most worried about.

00:44:37.310 --> 00:44:39.350
If someone compromises,
guesses, figures out

00:44:39.350 --> 00:44:41.970
your main password that
protects all of the others,

00:44:41.970 --> 00:44:44.570
now you've just handed them
all of your accounts at once.

00:44:44.570 --> 00:44:46.590
And that's a massive trade-off.

00:44:46.590 --> 00:44:48.980
However, if you again
consider the alternative,

00:44:48.980 --> 00:44:53.090
coming up with big random passwords and
then memorizing them all, or somewhat

00:44:53.090 --> 00:44:55.010
foolishly, writing them
down on a Post-It note

00:44:55.010 --> 00:44:56.843
and putting it on your
monitor, the question

00:44:56.843 --> 00:45:02.450
shouldn't be is this the
right way to do things,

00:45:02.450 --> 00:45:05.702
but really, relatively speaking,
is this a better way to do things?

00:45:05.702 --> 00:45:07.910
So you're always going to
be vulnerable to some risk.

00:45:07.910 --> 00:45:09.590
Which of those risks do you worry about?

00:45:09.590 --> 00:45:12.380
And maybe you can mitigate
that concern by maybe

00:45:12.380 --> 00:45:15.920
you could write down your main
password for your password manager

00:45:15.920 --> 00:45:20.390
and maybe put it in a physical
vault or a fire locker or the like

00:45:20.390 --> 00:45:23.260
that with very low probability
someone else would get access to,

00:45:23.260 --> 00:45:25.010
unless they physically
attack that device,

00:45:25.010 --> 00:45:27.960
or hide it somewhere in a book
on your shelf or the like.

00:45:27.960 --> 00:45:29.510
So that yes, it's vulnerable.

00:45:29.510 --> 00:45:33.140
But the odds that someone finds
it might just be relatively low.

00:45:33.140 --> 00:45:35.630
But again, this is the
theme, figuring out

00:45:35.630 --> 00:45:39.170
what the right balance is for your
accounts and the type of security

00:45:39.170 --> 00:45:42.140
that you want to aspire to achieve.

00:45:42.140 --> 00:45:43.890
Well, let's consider
a few other defenses.

00:45:43.890 --> 00:45:46.932
And we'll leave time at the very end
for questions about particular tools

00:45:46.932 --> 00:45:47.632
and techniques.

00:45:47.632 --> 00:45:49.340
What's another building
block that we can

00:45:49.340 --> 00:45:52.310
bring to bear when it comes to
protecting ourselves online?

00:45:52.310 --> 00:45:55.850
So encryption-- CS50 students will
know that encryption refers, again,

00:45:55.850 --> 00:46:01.010
to the scrambling of information,
making data look like it's random data,

00:46:01.010 --> 00:46:05.000
but by encrypting it with what's called
the key, typically, a key that only you

00:46:05.000 --> 00:46:06.890
and the recipient somehow know.

00:46:06.890 --> 00:46:10.070
Encryption tends to be the
solution to a lot of our problems.

00:46:10.070 --> 00:46:12.650
And indeed, these password
managers typically

00:46:12.650 --> 00:46:17.150
additionally encrypt your data so that
even someone who steals your Mac and PC

00:46:17.150 --> 00:46:19.370
can't just open up the
program and see it.

00:46:19.370 --> 00:46:21.620
All of the data, too,
is similarly encrypted.

00:46:21.620 --> 00:46:26.030
Many of you have already been trained or
conditioned by society to at least look

00:46:26.030 --> 00:46:30.815
for or hope for or recognize https://.

00:46:30.815 --> 00:46:32.425
The s means secure.

00:46:32.425 --> 00:46:34.550
That just tends to be a
good thing because it means

00:46:34.550 --> 00:46:36.290
a website you're visiting is secure.

00:46:36.290 --> 00:46:39.830
It's encrypted, as opposed
to just http, which

00:46:39.830 --> 00:46:43.620
was much more common just a few years
ago and is completely unencrypted.

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

00:46:48.260 --> 00:46:51.960
between you and that website
theoretically can be listening in,

00:46:51.960 --> 00:46:55.460
so to speak, on your traffic, the
zeros and ones going back and forth.

00:46:55.460 --> 00:46:57.410
Anyone can see what
pages you're visiting.

00:46:57.410 --> 00:47:00.260
If you're in some foreign country
visiting sensitive materials,

00:47:00.260 --> 00:47:02.840
the government could know
what websites you're visiting

00:47:02.840 --> 00:47:05.400
and what content, for
instance, you're reading.

00:47:05.400 --> 00:47:07.940
https makes that much harder.

00:47:07.940 --> 00:47:09.080
It's not 100%.

00:47:09.080 --> 00:47:10.940
There are attacks still
that are possible.

00:47:10.940 --> 00:47:12.800
But again, it just raises the bar.

00:47:12.800 --> 00:47:15.667
But there's another
technique that's increasingly

00:47:15.667 --> 00:47:18.500
being discussed in the media, and
with which you should be familiar,

00:47:18.500 --> 00:47:20.690
known as end-to-end encryption.

00:47:20.690 --> 00:47:24.890
End-to-end encryption means that when
you're using a third-party service,

00:47:24.890 --> 00:47:27.980
typically, whether it's a chat
service, a video conferencing

00:47:27.980 --> 00:47:30.320
service or the like,
you're not just encrypting

00:47:30.320 --> 00:47:33.590
your traffic, the zeros
and ones, between you

00:47:33.590 --> 00:47:39.020
and Google, you and Microsoft, you
and Amazon, or some other third-party.

00:47:39.020 --> 00:47:43.310
You are encrypting your data between
you and the person you're talking to.

00:47:43.310 --> 00:47:46.580
So WhatsApp, for instance,
the popular messaging tool,

00:47:46.580 --> 00:47:48.140
early on had this feature.

00:47:48.140 --> 00:47:50.670
And many other chat programs
nowadays have it as well,

00:47:50.670 --> 00:47:54.805
including iMessage and Signal
and Telegram and the like.

00:47:54.805 --> 00:47:56.930
End-to-end encryption means
that even though you're

00:47:56.930 --> 00:48:01.520
using a third-party service, a
company that you may or may not trust,

00:48:01.520 --> 00:48:06.050
your communications are communicated
between you and the person

00:48:06.050 --> 00:48:08.190
with whom you're speaking.

00:48:08.190 --> 00:48:12.260
The company in between, their servers,
even though your data is going through

00:48:12.260 --> 00:48:15.530
their servers, cannot
decrypt that information.

00:48:15.530 --> 00:48:18.232
They cannot see the
information in its raw form.

00:48:18.232 --> 00:48:19.190
So that's a good thing.

00:48:21.760 --> 00:48:23.140
So WhatsApp does this, too.

00:48:23.140 --> 00:48:28.100
Zoom kind of does this, at
least, only recently does this.

00:48:28.100 --> 00:48:31.030
So Zoom, for instance, the technology
that we are all using right now,

00:48:31.030 --> 00:48:33.580
actually took some flak,
rightly so, some months

00:48:33.580 --> 00:48:36.700
back, when in their marketing literature
on their website, as I recall,

00:48:36.700 --> 00:48:40.510
advertised Zoom as offering
end-to-end encryption, which

00:48:40.510 --> 00:48:43.750
was false because what
end-to-end encryption means is,

00:48:43.750 --> 00:48:47.620
as I described it, between you and the
person with whom you're communicating.

00:48:47.620 --> 00:48:50.890
But the marketing
literature at the time was

00:48:50.890 --> 00:48:53.410
referring to end-to-end
encryption between you

00:48:53.410 --> 00:48:57.430
and Zoom, which is not what security
researchers or computer scientists

00:48:57.430 --> 00:49:00.970
or technologists in general would
define end-to-end encryption as.

00:49:00.970 --> 00:49:03.130
And so they took some
flak for that, rightly so.

00:49:03.130 --> 00:49:05.650
They've begun, though, in
recent weeks, rolling out

00:49:05.650 --> 00:49:08.140
actual end-to-end encryption.

00:49:08.140 --> 00:49:10.270
We are not using it right now.

00:49:10.270 --> 00:49:12.880
It actually makes certain
features harder to use.

00:49:12.880 --> 00:49:14.530
So there, too, there's a trade-off.

00:49:14.530 --> 00:49:17.590
But generally speaking, if you're
having the most intimate or private

00:49:17.590 --> 00:49:22.150
or personal or financial or medical
of communications with people,

00:49:22.150 --> 00:49:27.010
this is another feature you should start
to look for and listen for and expect

00:49:27.010 --> 00:49:28.810
of the tools that you're using.

00:49:28.810 --> 00:49:32.440
And especially when it comes to
censorship in various countries

00:49:32.440 --> 00:49:35.290
and communities, this
is the kind of software

00:49:35.290 --> 00:49:37.330
that's increasingly under
attack by governments

00:49:37.330 --> 00:49:42.730
because they often want backdoor
so that the USA's NSA or FBI

00:49:42.730 --> 00:49:45.130
or some other entity can get
into these communications.

00:49:45.130 --> 00:49:47.650
That's made much more
difficult, in a good way,

00:49:47.650 --> 00:49:53.170
by using end-to-end encryption so that
your communications are indeed secure.

00:49:53.170 --> 00:49:56.757
Well, in our final moments together,
let's focus ultimately on Zoom,

00:49:56.757 --> 00:49:58.090
the very technology we're using.

00:49:58.090 --> 00:49:59.950
Because they've taken
some flak, certainly

00:49:59.950 --> 00:50:02.825
beyond end-to-end encryption, which
you might not have even heard of,

00:50:02.825 --> 00:50:04.210
as just being insecure.

00:50:04.210 --> 00:50:06.640
And a lot of school
systems, a lot of users

00:50:06.640 --> 00:50:09.680
decided some months ago to stop
using Zoom for this reason,

00:50:09.680 --> 00:50:12.040
even though their
business is still booming.

00:50:12.040 --> 00:50:13.630
So is Zoom secure?

00:50:13.630 --> 00:50:15.640
Let's ask one final
question of the group

00:50:15.640 --> 00:50:19.690
here, keeping in mind that we've now
just spent the past hour discussing

00:50:19.690 --> 00:50:21.250
topics of security.

00:50:21.250 --> 00:50:23.990
Let me go ahead and ask
this final question here,

00:50:23.990 --> 00:50:26.920
which will appear on your
screen in just a moment.

00:50:26.920 --> 00:50:32.450
It is quite simply, is Zoom secure?

00:50:32.450 --> 00:50:34.860
All right, let's see how
the responses are coming in.

00:50:34.860 --> 00:50:41.690
I'm seeing 55% no, 16% yes, 28%, unsure.

00:50:41.690 --> 00:50:43.070
So a reasonable spread there.

00:50:43.070 --> 00:50:44.780
Let's take a couple of comments here.

00:50:44.780 --> 00:50:50.120
Among those of you who think Zoom is
secure, why do you think it's secure?

00:50:50.120 --> 00:50:54.080
Would anyone be comfortable raising
a virtual hand so we can call on you,

00:50:54.080 --> 00:50:58.490
or maybe commenting in the chat as
to why you think Zoom is secure?

00:50:58.490 --> 00:51:01.640
Let's see, over to, how about, Sam?

00:51:01.640 --> 00:51:02.390
What do you think?

00:51:02.390 --> 00:51:07.760
SAM: Two days ago, Zoom offered
end-to-end encryption to all the users.

00:51:07.760 --> 00:51:10.730
DAVID J. MALAN: Yeah, so it
was, in fact, that timely.

00:51:10.730 --> 00:51:12.497
Zoom began rolling
out, on a trial basis,

00:51:12.497 --> 00:51:14.580
essentially, end-to-end
encryption with all users.

00:51:14.580 --> 00:51:18.290
So if you are using that,
and-- and this is key, too--

00:51:18.290 --> 00:51:22.310
and Zoom has implemented
that concept correctly,

00:51:22.310 --> 00:51:24.920
then, yes, maybe Zoom
is secure in the sense

00:51:24.920 --> 00:51:27.470
that your video conversation
with someone else

00:51:27.470 --> 00:51:29.960
is in fact private between you and them.

00:51:29.960 --> 00:51:34.370
With that said, if you're in a
coffee shop or in a library, at least

00:51:34.370 --> 00:51:37.580
in healthier times, and someone's
looking over or listening

00:51:37.580 --> 00:51:41.080
in on your conversation, arguably
even that technology is not secure.

00:51:41.080 --> 00:51:42.830
You can imagine there
being other threats.

00:51:42.830 --> 00:51:47.570
Maybe you have accidentally been
vulnerable to a virus, some kind

00:51:47.570 --> 00:51:49.067
of threat on your own computer.

00:51:49.067 --> 00:51:50.900
And even though, yes,
your data is encrypted

00:51:50.900 --> 00:51:53.480
between you and that
other person, that doesn't

00:51:53.480 --> 00:51:56.420
mean there's not malicious software
running on your own personal Mac

00:51:56.420 --> 00:51:59.630
or PC or the other person's,
recording everything

00:51:59.630 --> 00:52:02.750
you say and uploading it to
some third-party adversary.

00:52:02.750 --> 00:52:06.950
So there, too, whenever you ask or
answer questions about security,

00:52:06.950 --> 00:52:09.800
take into account those
kinds of qualifications,

00:52:09.800 --> 00:52:14.383
those conditionals, because
security should never

00:52:14.383 --> 00:52:15.800
be discussed, really, in a vacuum.

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.

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

00:52:23.000 --> 00:52:26.300
Zoom took was overstated because
those criticizing didn't really

00:52:26.300 --> 00:52:29.860
understand some of the issues that
were being touted in the media.

00:52:29.860 --> 00:52:36.050
So for instance, all of you today, to
log into this meeting, for instance,

00:52:36.050 --> 00:52:38.810
followed a URL, most likely,
that you had been emailed

00:52:38.810 --> 00:52:40.160
or that you saw on your screen.

00:52:40.160 --> 00:52:44.630
And that URL probably looked a little
something like this-- https://,

00:52:44.630 --> 00:52:48.620
which is good, zoom.us or something
like that, followed by a number,

00:52:48.620 --> 00:52:49.700
the meeting ID--

00:52:49.700 --> 00:52:52.250
for instance, 5551112222.

00:52:52.250 --> 00:52:55.560
But it was a different
number for today's meeting.

00:52:55.560 --> 00:52:58.970
So if you received this URL
after registering, is it secure?

00:52:58.970 --> 00:53:02.870
Well, even though all of you here
right now have presumably registered,

00:53:02.870 --> 00:53:05.750
technically there was
nothing stopping any of you

00:53:05.750 --> 00:53:10.820
from texting or emailing
or DMing this same URL

00:53:10.820 --> 00:53:12.290
to anyone else on the internet.

00:53:12.290 --> 00:53:14.790
And they could therefore join,
perhaps, without registering.

00:53:14.790 --> 00:53:17.720
So maybe that's a threat,
though, Zoom typically sends you

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.

00:53:21.770 --> 00:53:24.020
And there's another detail
that some URLs have,

00:53:24.020 --> 00:53:25.880
too, which might look like this--

00:53:25.880 --> 00:53:29.058
a question mark at the
end, and pwd for password,

00:53:29.058 --> 00:53:30.350
and then some kind of password.

00:53:30.350 --> 00:53:33.290
And indeed, the URLs you clicked
today looked a little more like that,

00:53:33.290 --> 00:53:37.130
still different because they
were special registration URLs.

00:53:37.130 --> 00:53:40.670
But here, if your URL has
this password, now you

00:53:40.670 --> 00:53:43.280
need to know both the
meeting ID and the password

00:53:43.280 --> 00:53:45.555
in order to join that
particular Zoom meeting.

00:53:45.555 --> 00:53:48.680
And if you're not running big classes,
like we are today with this meeting,

00:53:48.680 --> 00:53:51.980
but rather you're having one-on-one
or smaller scale meetings,

00:53:51.980 --> 00:53:56.480
typically you are receiving or
generating a URL that looks like this,

00:53:56.480 --> 00:53:59.570
or better yet, that looks
like this, so that it

00:53:59.570 --> 00:54:02.660
doesn't suffice for an adversary
to just guess the meeting ID.

00:54:02.660 --> 00:54:04.670
And that's what was happening early on.

00:54:04.670 --> 00:54:07.520
Zoom typically did not
require that people

00:54:07.520 --> 00:54:10.820
choose passwords for their meetings,
which meant the only thing between you

00:54:10.820 --> 00:54:14.090
and some adversary Zoombombing
you, so to speak, hacking

00:54:14.090 --> 00:54:17.130
into your meeting, which they
just had to guess the meeting ID.

00:54:17.130 --> 00:54:19.580
And we've seen already it
took me, what, like 1 minute,

00:54:19.580 --> 00:54:22.310
30 seconds to write
a Python program that

00:54:22.310 --> 00:54:26.780
just generated all possible numbers
of length four or eight or whatever.

00:54:26.780 --> 00:54:29.570
So people with too much
free time are writing

00:54:29.570 --> 00:54:32.330
code that just tries all possible URLs.

00:54:32.330 --> 00:54:35.240
And so if you've ever been
Zoombombed, maybe that's

00:54:35.240 --> 00:54:38.120
because someone shared the URL
with someone they shouldn't have.

00:54:38.120 --> 00:54:42.140
Or maybe someone with a bit of
programming experience or just luck

00:54:42.140 --> 00:54:43.880
guessed your meeting ID.

00:54:43.880 --> 00:54:47.330
So this was a feature in
the sense that, honestly,

00:54:47.330 --> 00:54:50.270
having to type in a meeting ID
and a password is just annoying.

00:54:50.270 --> 00:54:52.830
It starts to hurt the
usability of the system.

00:54:52.830 --> 00:54:55.070
And a lot of people in
the corporate world,

00:54:55.070 --> 00:54:58.130
they're going to choose another
product if another product is easier

00:54:58.130 --> 00:54:59.870
to start the video conference with.

00:54:59.870 --> 00:55:02.300
So arguably, it was a conscious
decision on Zoom's part.

00:55:02.300 --> 00:55:04.092
Now universities and
companies have started

00:55:04.092 --> 00:55:07.175
requiring this or another feature
called a waiting room, which some of you

00:55:07.175 --> 00:55:08.510
might have experienced today.

00:55:08.510 --> 00:55:12.680
But that just, again, raises the
bar to someone attacking the system.

00:55:12.680 --> 00:55:14.210
So is Zoom secure?

00:55:14.210 --> 00:55:15.440
Yes and no.

00:55:15.440 --> 00:55:17.660
It really should be
considered not in a vacuum,

00:55:17.660 --> 00:55:21.110
but in the context of what kinds
of threats are you worried about

00:55:21.110 --> 00:55:25.400
and what kinds of defenses
are you willing to put up?

00:55:25.400 --> 00:55:31.040
So just like in the real world, you
might have your own home or apartment

00:55:31.040 --> 00:55:36.840
or the like, on which you might have
locks and bolts and bars on the window.

00:55:36.840 --> 00:55:39.240
At some point, if it takes
you five minutes to unlock

00:55:39.240 --> 00:55:41.940
every lock on your door
just to get into your home,

00:55:41.940 --> 00:55:44.160
it might be much more
secure, but you're probably

00:55:44.160 --> 00:55:47.280
not going to enjoy going home
because it takes that long to get in.

00:55:47.280 --> 00:55:50.310
And you might put bars on the window
to keep that person physically out,

00:55:50.310 --> 00:55:52.380
but it's not going to
look particularly nice.

00:55:52.380 --> 00:55:54.797
And there's nothing stopping
them from going one floor up.

00:55:54.797 --> 00:55:56.580
So there, too, there's this trade-off.

00:55:56.580 --> 00:55:59.130
And so among the takeaways,
we hope, from today, are

00:55:59.130 --> 00:56:01.260
one, just better thought
processes when it

00:56:01.260 --> 00:56:04.530
comes to what does it mean for
your phone or your computer

00:56:04.530 --> 00:56:06.573
or your homes for that
matter to be secure,

00:56:06.573 --> 00:56:09.240
and to recognize that there's
always going to be some trade-off.

00:56:09.240 --> 00:56:12.460
And we would encourage you, ultimately,
to ask these kinds of questions.

00:56:12.460 --> 00:56:16.210
If any company, if any app, if any
website just says on their website,

00:56:16.210 --> 00:56:18.690
"we are secure," that's nonsense.

00:56:18.690 --> 00:56:22.410
That means nothing in and of itself
until you start asking questions, like,

00:56:22.410 --> 00:56:25.890
what are you secure against, and how?

00:56:25.890 --> 00:56:27.760
Well, thank you so much
for joining us here.

00:56:27.760 --> 00:56:28.890
Let's officially wrap here.

00:56:28.890 --> 00:56:32.250
But folks are welcome to stick
around for some more time

00:56:32.250 --> 00:56:34.720
if you'd like to ask
questions in the group.

00:56:34.720 --> 00:56:37.500
But if you have to take off,
please feel free to head out.

00:56:37.500 --> 00:56:39.650
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