# Encryption Part 1

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>> Hi and welcome to lesson 2.3.

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In this lesson, we're going to talk

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about the network layer.

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Everything in the last couple of lessons,

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we've been talking about the perimeter,

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which is that boundary between

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our internal devices in that external entity.

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Now we're going to move a little bit more

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inward on that layered approach.

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We're going to talk about the network layer,

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which is all of that

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backbone infrastructure, the routers,

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and switches that connect us to

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the outside world as well as

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connect devices together internally.

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Now within the network layer,

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we're going to talk about a few different components.

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One is encryption. We're going to talk about it.

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We touched on encryption before

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a little bit when we talked about VPNs,

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but in this lesson, we're going to go into how encryption

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works and dive in a little bit

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deeper on encryption itself.

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We're going to talk about web proxies.

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Web proxies are basically

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those devices that help us control

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how our organization interacts

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with the Internet and with the outside web.

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We're going to talk about NAC,

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which is network access control.

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That's all about how we allow devices

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onto our network and what types of

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devices we allow onto our network.

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Then we'll get into a little bit about wireless security

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towards the end of the lesson

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and towards the end of the module.

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Let's start with encryption.

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Encryption in its basic form,

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before we start to actually talk about functionality.

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Let's talk about some definitions because

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we're going to use these over and over again.

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When we say the word algorithm,

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we're referring to a mathematical formula

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used for encrypting.

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It's actually a formula,

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a plus b equals c. When we talk about the word key,

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we're talking about a secret variable.

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It's something that's secret.

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It's a variable that's used

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within that encryption algorithm.

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If the algorithm is x plus one equals 3,

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then x is our key.

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It's what's unknown, it's what is secret,

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it's what we have to solve for.

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When we use the term ciphertext,

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we're talking about the data

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that's actually been encrypted.

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Once the data is encrypted and we transmit

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it across the wire in an encrypted format,

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that's what we refer to sometimes as ciphertext.

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Symmetric encryption is encryption where

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both sides are using the same key,

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so that same secret or variable

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is hard-coded or is known by

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both sides of the equation whereas

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asymmetric encryption is where

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each party on each side uses a different key.

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Then finally, public key encryption is

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an encryption mechanism that uses

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both asymmetric and symmetric encryption.

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We're going to show you

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that towards the end of this lesson.

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Let's talk about how encryption works.

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In its most basic form,

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encryption is just creating a secret.

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It's just scrambling data in a way

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that others who don't know the secret can't read it.

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Let's say we've got this computer over here on

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the left that wants to communicate

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with computer on the right.

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What it actually wants to communicate is a password.

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In this case, we've got a password in

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clear text and our password is not on my watch.

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The computer on the left is going

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to send that password through

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an encryption process and

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that process is simply taking the data,

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which is the password, and applying it to an algorithm.

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The output of that is going to be our ciphertext.

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This ciphertext is nothing but jumbled-up data.

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It's just random characters that if we transmit that

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over the wire and someone

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happens to see that or intercept that,

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they're not going to have any idea what that

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means because it's gobbledygook.

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It doesn't mean anything.

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Computer on the right is going to

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receive that ciphertext,

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it's going to run it through a decryption process,

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which is simply applying it to that algorithm

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again and the output is going to be the clear text.

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Now the computer on the right can

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read the actual clear text.

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That's all encryption is.

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At its highest level,

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that's all it's really doing.

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It's very complicated, the mechanisms that do that,

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but at its highest level, that's what it is.

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Now, let's get into

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a little bit more details about

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the keys and the algorithms.

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First off, keys, as I said,

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are mathematical formulas used

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in the encryption and decryption process.

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But algorithms are not secret.

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Algorithms are actually public.

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There's plenty of them out there.

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There's a handful of them that are stronger than others.

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They're all publicly available.

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They're not any secrets at all.

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The formulas themselves are not secrets.

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But our secrets are the keys,

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and those are the things that we need to keep quiet,

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keep a secret and protect

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because if you know the algorithm because it's public,

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and you acquire the key,

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then you can solve the equation

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and you can read the data.

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Good algorithms use a combination

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of both keys and the data

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itself to populate parts

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of the formula to make them more complex.

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If we're starting, we want to encrypt some data.

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We actually have two secrets when we start,

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we have the key which we know, and that's our secret.

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We also have the data.

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If we haven't transmitted that data yet,

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that data is secret as well,

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and we can use that as part of our algorithm.

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