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- Welcome to lesson four,

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Explain the Importance of Using

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Appropriate Cryptographic Solutions.

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Now, this is a first of many
lessons about cryptography,

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and, as I mentioned in the intro,

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really one of my favorite topics.

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You may find this topic to be challenging,

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so just kinda stick with it.

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And if it doesn't resonate the first time,

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don't hesitate to go through the lessons

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one more time, two more
times, three more times,

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until, all of a sudden,
you have that aha moment

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and you're like, "Oh yeah, I get it now."

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So we're gonna start off in
4.1 with a cryptography primer.

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Now, traditional cryptography,

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and traditional cryptography goes

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way back into ancient times,

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is a conversion of communication

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into a form that can only be
read by the intended recipient.

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I want you to imagine, in ancient times,

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a massive battle going on

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and we've got generals on both sides.

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And one general wants to get a message

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to his frontline troops,

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but really worried that
what if the messenger

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got captured and got sent
to the other general,

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would they be able to read the message?

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And so they wanted to have some way

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to make that message unreadable,

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and that was a traditional
application of cryptography.

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Now, modern cryptography

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has really widened that
historical definition

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to also include the
assurance of integrity,

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that the message is trustworthy,

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that it hasn't been
changed in transmission,

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and sender identity.

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We know exactly who
that message came from.

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When we talk about
cryptography from a high level,

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we'll use the term PKI.

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It stands for public key Infrastructure.

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And public key infrastructure
really encompasses

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all of the programs, the
data formats, the procedures

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the communication protocols,
the security policies,

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and the public key
cryptographic mechanisms

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that work together in
a comprehensive manner

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to enable secure communication.

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So I wanna introduce you to
four cryptographic solutions

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and, most importantly, their use case,

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encryption, hashing, digital signatures,

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and digital certificates.

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Now, in this lesson,

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I'm just gonna introduce
you to each of them,

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and then we will do lessons
specifically on that.

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We have a lesson on encryption,
a lesson on hashing,

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a lesson on digital signatures,

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and a lesson on digital certificates.

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Encryption is a process
of encoding information.

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It's really making information unreadable.

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When you open up and
you look at the message,

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you're like, "That's gibberish.

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What does it mean?"

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So the use case of encryption
is confidentiality.

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Hashing is a one-way function

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that turns a file or a string
of text into a unique digest,

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sometimes called a fingerprint,

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which is just a number a bunch
of values of the message.

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Now, the use case for hashing
is going to be integrity.

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Then we have digital signatures.

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Digital signature's actually a hash value

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that's been encrypted with
the sender's private key.

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That sounds a little confusing right now.

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Don't worry about it.

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What you need to know right now

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is the use case is sender authenticity

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that we know who the sender was,

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and non-repudiation,

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that the sender cannot deny
that they sent the message.

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And then we have digital certificates.

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And digital certificates
is a digital object

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that is tied to a cryptographic key pair.

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We haven't talked about
this yet, so don't worry.

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But the use case for a digital certificate

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is authentication.

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It's how we can authenticate someone.

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When a server says, "I am this server,"

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when the code says, "I am this code,"

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when the patch says, "I am this code,"

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it will be from their digital
certificate that we can say,

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"Okay, you are who you say you are."

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So encryption for confidentiality,
hashing for integrity,

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digital signatures for sender

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authentication and non-repudiation,

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and digital certificates
for authentication.

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We've got lots of terms to
go through in this lesson.

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We're gonna start with talking
about what a cipher is.

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A cipher is just a technique
that transforms plain text

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into cipher text and back to plain text.

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We have had cipher since ancient times.

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The Caesar cipher was just

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move every character three places over.

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So we would substitute a D
for an A, and an E for a B.

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So it's just the technique that allows us

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to transform our plain
text into cipher text

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and back to plain text.

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Plain text is just human readable text.

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It's what you see on
your screen right now.

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Cipher text is either
text that's been encrypted

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or in some form is human unreadable.

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It's it's letters, but it
doesn't mean anything to you.

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An algorithm is nothing
more than a mathematically

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complex modern cipher.

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I'll say that again,

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an algorithm is a mathematically
complex modern cipher

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that we need to have a computer to solve.

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Now, algorithms are generally well known.

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They're published.

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They're really public information.

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A key, also called a crypto variable,

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is going to be a secret value
that we use with an algorithm.

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Because if everybody knows
what the algorithm is,

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then how do we use it for secrecy.

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We have to have a secret component.

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And the secret component that we use

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in conjunction with the algorithm

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is going to be known as a key.

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Now, a stream cipher is
going to be a cipher,

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remember, that's just a technique

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that transforms plain text
into cipher text and back,

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is an algorithm that works
on one bit of data at a time,

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using these XOR functions.

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When I have to imagine a stream cipher,

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I always think of a
faucet that's dripping.

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Drip, drip, drip.

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And each of those drips in
my mind is one bit at a time.

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And so my algorithm would work
on each one of those drip.

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Drip, drip.

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A block cipher is an algorithm

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that works with a block of data.

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Could be a 56k block,
64k block, 128k block,

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could be a 256k block.

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It's just a block of data.

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Confusion is a process of changing values.

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So complex substitution functions

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are used to create confusion.

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And lastly, diffusion is the
process of changing the order.

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So sending bits through
multiple rounds of transposition

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is used to create diffusion.

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Okay, so I just introduced you to key.

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Let's talk more about a key.

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A key is a secret value
used with an algorithm.

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The key can dictate

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what parts of the algorithm
are gonna be used,

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in what order, and with what values.

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'Cause remember, the
algorithms are published.

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They're known.

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So the key is what provides
the secret part of it.

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Now, when you hear the term key space,

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it's really just the number
of possible key combinations.

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So a 256 bit key is two
to the 256 bit power.

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That's a lot of combinations.

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Because a key is really just a value.

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It's really just a set of numbers.

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So two to the 256, lots of options there.

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Key stretching is a
technique that can be used

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to strengthen a weak key.

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So maybe we had a 56 bit key.

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We can strengthen a weak
key into a stronger key.

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We often use that to protect
against brute force attacks.

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When you hear the term symmetric key,

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we mean one key, a single key.

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Sometimes it'll be referred
to as symmetric key.

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Sometimes it'll be referred
to as a secret key.

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Sometimes it'll be referred
to as a shared key.

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Sometimes it'll be refer
to as a single key.

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All of those mean the same thing.

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And what it means is
that we use the same key

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to encrypt as we do to decrypt.

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Think about the key that you use

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to get into your house or your apartment.

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You use the same key to unlock your door

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as you do to lock your door.

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Think about the key that
you use to start your car.

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Whether it's push button

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or you actually still turn the key,

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You use the same key to turn your car on

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as you do to turn it
off, that's symmetric.

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Asymmetric says that we
need to use two keys.

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They're gonna be mathematically related.

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We use one for encryption
and one for decryption.

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Now, both of them can do either function.

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Both can encrypt or decrypt,

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but you always have to use
'em in a pair configuration.

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Now we wanna make sure
that we secure our key.

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If we have just one key,

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so a symmetric key, a
single key, a shared key,

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even called a session key sometimes,

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we always wanna make sure that

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we're really keeping it secret.

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In a key pair, we're
going to have asymmetric.

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We're going to have one key
that is publicly distributed

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and one that is private
and must be kept secret.

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So for our private key
and for our symmetric key,

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we need to look at ways to really ensure

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the secrecy of that key.

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And there are a couple
of different options.

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There's a TPM, a trusted platform module.

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There's a secure enclave.

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There's an HSM that stands
for hardware security module,

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and there's the option of key escrow.

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A TPM is a hardware chip

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used for storing cryptographic keys

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and related information.

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A secure enclave is a separate
processor and microkernel

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that's used specifically
for storing and processing

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cryptographic keys and related information

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in mobile devices.

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An HSM is a hardened
tamper-resistant hardware device

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that we can use to
secure cryptographic keys

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and, again, related information.

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And key escrow is just
a safe keeping mechanism

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for storing and obtaining copies of keys

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that are needed to decrypt encrypted data

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under certain conditions
or certain circumstances,

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so you may give your attorney
right a copy of the key,

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and that key can only be used
in certain circumstances.

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Now, the strength of the crypto system

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is gonna be a combination
of a lot of factors.

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The algorithm, we'll be talking about

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lots of different algorithms shortly.

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The algorithmic process,

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the length of the key,

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and the secrecy of the key.

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And if any one element is weak,

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well, the crypto system can
potentially be compromised.

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Now there are two terms
you're going to hear

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in relation to cryptographic strength.

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One is deprecated and the other is broken.

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Deprecated means that
the use of the algorithm,

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or the key length, or
the process is allowed,

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but the user must accept some risk

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due to inherent weaknesses.

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So you can use it, but you
need to know it's weak,

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and an example is the 3DES algorithm,

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and we'll talk more about that shortly.

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Broken means either the
key and/or the key length

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or the processes behind it is exploitable,

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which means it's not
gonna secure you anymore.

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So deprecated is weak.

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Broken is exploitable.

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That's the end of our primer.

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That's gonna bring us to
a three-second challenge.

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Then we'll go off into
lessons about encryption,

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and hashing, and digital signatures,

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and digital certificates as
well as emerging cryptography.

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So three second challenge, are you ready?

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Five challenge questions,
three seconds each.

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I know you can do these.

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One, two, three. Let's start.

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A mathematically complex
modern cipher is a...

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One, two, three.

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That's an algorithm.

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Secret value that's
used with an algorithm.

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One, two, three.

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That's gonna be a key.

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And if you said crypto
variable, well, you're very cool

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'cause it's also a crypto variable.

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All right, number three.

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The term used to describe a
weak cryptographic element.

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One, two, three.

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That's gonna be deprecated number.

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Remember deprecated if it's weak.

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Broken if it's been exploited.

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Number four, a separate
processor and microkernel

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used for storing and
processing cryptographic keys

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in mobile devices.

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It's important in mobile devices.

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One, two, three.

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That's gonna be a secure enclave.

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And lastly, number five.

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The number of possible key combinations.

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So I'm not asking you to give me a number.

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I'm asking you to tell me
what is that referred to,

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the number of possible key combinations.

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One, two, three.

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And that's your key space.

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All right, let's do our first

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cryptographic security in action.

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This is about key security.

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Your municipal employer,
Anytown Revenue Service,

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wants to encrypt taxpayer data at rest.

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Now, it's important that they adhere

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to government standards,

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so they're planning on
using 3DES algorithm

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for symmetric encryption.

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Now, I get that we haven't talked about

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symmetric encryption yet.

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We haven't talked about 3DES,

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but just kinda go with it.

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Now, they wanna make sure
that internal employees

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have easy access to the data,

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so they plan to publish the key

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on their intranet.

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Now, symmetric, what does that mean?

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Symmetric means there's one key,

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shared key, single key,
secret key, session key,

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one key to encrypt and decrypt.

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So here's the important thing.

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They wanna make sure
the internal employees

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have easy access to data,

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so they plan to publish
the key on their intranet.

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So do you have any concerns
about this approach?

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Go ahead and put me on
pause, jot down some notes.

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Let me know if you have any
concerns about their approach.

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00:13:31,410 --> 00:13:32,463
Well, I hope you do.

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00:13:33,600 --> 00:13:35,370
The strength of the crypto system

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00:13:35,370 --> 00:13:38,760
is a combination of the algorithm,
the algorithmic process,

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the length of the key, and
the secrecy of the key.

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Now, we weren't really
asked to comment here about

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whether they're using
symmetric or asymmetric,

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or the fact they're gonna
use a 3DES algorithm.

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00:13:49,560 --> 00:13:51,750
What we really are commenting on is

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publishing the key on their intranet.

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But I will tell you
that 3DES is deprecated

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and shouldn't be used.

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Again, you wouldn't have
necessarily known that yet.

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The AES has replaced 3DES as
the US government standard.

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Again, not something you
necessarily would've known yet.

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But here's what you should have known,

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that the security of symmetric encryption

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00:14:13,020 --> 00:14:15,150
depends upon the secrecy

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00:14:15,150 --> 00:14:18,480
of the single shared
crypto variable or key.

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That key, 100%, definitely,
definitely definitely

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00:14:22,680 --> 00:14:26,280
should not be published on their intranet.

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And knowing that, my friends,

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is absolutely security in action.

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All right, there you go.

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00:14:33,360 --> 00:14:35,070
That's your word cloud.
You know what to do.

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00:14:35,070 --> 00:14:37,290
I don't want you moving
on to the next lesson

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00:14:37,290 --> 00:14:40,200
until you're comfortable
with all these terms

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00:14:40,200 --> 00:14:42,900
and you're confident that
you can explain them.

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But when you're ready, head
on over to the next lesson,

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00:14:45,117 --> 00:14:47,040
and we're gonna be
talking about encryption.

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See you there.