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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