hi my name is MIA gillip nur I'm
majoring in computer science at UC
Berkeley and I work for the Department
of Defense where I try to keep
information safe the Internet is an open
and public system we all send and
receive information over shared wires
and connections but even though it's an
open system we still exchange a lot of
private data things like credit card
numbers bank information passwords and
emails so how is all this private stuff
kept secret data of any kind can be kept
secret through a process known as
encryption these scrambling or changing
of the message to hide the original text
now decryption is the process of
unscrambling that message to make it
readable this is a simple idea and
people have been doing it for centuries
one of the first well-known methods of
encryption was Caesar cipher named after
Julius Caesar a Roman general who
encrypted his military commands to make
sure that if a message was intercepted
by enemies they wouldn't be able to read
it
Caesar cipher is an algorithm that
substitutes each letter in the original
message with a letter a certain number
of steps down the alphabet if the number
is something only the sender and
receiver know then it's called the key
it allows the reader to unlock the
secret message for example if your
original message is hello then using the
Caesar cipher algorithm with a key of
five the encrypted message would be this
to decrypt the message the recipient
would simply use the key to reverse the
process but there's a big problem with
Caesar cipher anybody can easily break
or crack the encrypted message by trying
every possible key in the English
alphabet there are only 26 letters which
means you'd only need to try at most 26
keys to decrypt the message now trying
26 possible keys isn't very hard it
would take at most an hour
so let's make it harder instead of
shifting every letter by the same amount
let's shift each letter by a different
amount in this example a 10 digit key
shows how many positions each successive
letter will be changed to encrypt a
longer message guessing this key would
be really hard using 10 digit encryption
there could be 10 billion possible key
solutions obviously that's more than any
human could ever solve it would take
many centuries but an average computer
today would take just a few seconds to
try all 10 billion possibilities so in a
modern world where the bad guys are
armed with computers instead of pencils
how can you encrypt messages so securely
that they're too hard to crack now too
hard means that there are too many
possibilities to compute in a reasonable
amount of time
today's secure communications are
encrypted using 256 bit keys that means
a bad guys computer that intercepts your
message would need to try this many
possible options until they discover the
key and crack the message even if you
had a hundred thousand super computers
and each of them was able to try a
million billion keys every second it
would take trillions of trillions of
trillions of years to try every option
just to crack a single message protected
with 256 bit encryption of course
computer chips get twice as fast and the
size every year or so if that pace of
exponential progress continues today's
impossible problems will be solvable
just a few hundred years in the future
and 256 bits won't be enough to be safe
in fact we've already had to increase
the standard key length to keep up with
the speed of computers the good news is
using a longer key doesn't make
encrypting messages much harder but it
exponentially increases the number of
guesses that it would take to crack a
cipher when the sender and the receiver
share the same key to scramble and
unscramble a message it's called
symmetric encryption
with symmetric encryption like Caesar
cipher the secret key has to be agreed
on ahead of time by two people in
private
that's great for people but the Internet
is open and public so it's impossible
for two computers to meet in private to
agree on a secret key instead computers
use asymmetric keys a public key that
can be exchanged with anybody and a
private key that is not shared the
public key is used to encrypt data and
anybody can use it to create a secret
message but the secret can only be
decrypted by a computer with access to
the private key how this works is with
some math that we won't get into right
now think of it this way imagine that
you have a personal mailbox where
anybody can deposit mail but they need a
key to do it now you can make many
copies of the deposit key and send one
to your friend or even just make it
publicly available your friend or even a
stranger can use the public key to
access your deposit slot and drop a
message in but only you can open the
mailbox with your private key to access
all of the secret messages you've
received and you can send a secure
message back to your friend by using the
public deposit key to their mailbox this
way people can exchange secure messages
without ever needing to agree on a
private key public key cryptography is
the foundation of all secure messaging
on the open Internet including the
security protocols known as SSL and TLS
which protect us when we're browsing the
web your computer uses this today
anytime you see the little lock or the
letters HTTPS in your browser's address
bar this means your computer is using
public key encryption to exchange data
securely with the website you're on as
more and more people get on the internet
more and more private data will be
transmitted and the need to secure that
data will be even more important and as
computers become faster and faster
we'll have to develop new ways to make
encryption too hard for computers to
break
this is what I do with my work and it's
always changing
you