Cryptography Basics
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Time
15 hours 43 minutes
Difficulty
Advanced
CEU/CPE
16
Video Transcription
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>> Let's go ahead and pick up with
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the basis of cryptography.
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Now, I know some of you are cryptography experts.
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I also know that some of you are
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brand new to cryptography.
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That's generally the level that I like to teach,
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at least starting is I want to teach
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cryptography like you don't have
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experience or exposure to it.
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In that way, that just make sure that we're all
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starting from a level playing field and
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that we all have an understanding
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of some of these terms we're
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going to be throwing around while
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we do talk about crypto.
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If you are cryptography expert,
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you can just go to that happy place
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in your head where nothing bothers you.
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Then you can jump back in
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as we start to get to some more advanced ideas.
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Let's look at what we're going to cover in this section.
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This section we're going to focus
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on why we use cryptography?
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What services do we get from cryptography?
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Then we're going to talk about the elements that are
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necessary to take our plain,
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unencrypted text into ciphertext or encrypted text.
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Security services that are provided by cryptography.
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If you were to stop folks out in the street and say,
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"Why do we use cryptography?"
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I'll guarantee you almost every single person
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is going to say something to
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the effect of we use it
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for privacy, confidentiality, secrecy.
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That is absolutely right.
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Privacy is one of
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the main reasons that we use cryptography.
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We want to keep our secrets secret.
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Secrecy, privacy, confidentiality,
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those all go together and they're all about
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preventing unauthorized disclosure of information.
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The most common use of cryptography, absolutely.
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But we also have to
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consider cryptography for authenticity.
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Now when we talk about authenticity,
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authenticity allows us to verify a claimed identity.
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I claim to be Kelly Handerhan.
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But anybody can claim to be anybody.
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if I claim to be Kelly Handerhan,
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you should challenge me and say, "Prove it."
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I can prove my identity by using cryptography as well.
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Now the third service that we can get
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from cryptography is integrity.
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Integrity means that we want a means of
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detecting modification or corruption.
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Modification can be done.
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Corruption does modify files,
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but modification can also
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entail malicious modification as well.
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I want an assurance that
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the message or the content has not changed.
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I can get that with cryptography also.
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Then the last desirable security service
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is non-repudiation.
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Non-repudiation is a combination
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of authenticity and integrity.
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Basically what that says is that if I send a message,
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"I can't say, that message didn't come from
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me," and I also can't dispute its contents.
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I can't say, "The message came from me,
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but the contents must have changed."
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Really non-repudiation is a combination of
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authenticity and integrity together.
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A sender can't dispute having sent the message,
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and they can't dispute
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the contents of the message as well.
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If you're ever curious about
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what services cryptography can provide,
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think about the pain of cryptography; privacy,
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authenticity, integrity, and non-repudiation.
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Now I'll also mention that I
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want you to have this concept in mind.
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I'm going to give you a little formula here.
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Plain text plus initialization vector plus an algorithm
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plus a key are
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used to take this plain text into ciphertext.
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When you combine those, ideally,
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you'll produce ciphertext which is encrypted text.
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We're going to go into the details of
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what an initialization vector is, what's an algorithm?
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What's a key and how did they work
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together in the next section.
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That's going to be your cliffhanger to have
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you running on to the next segment.
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But in this section,
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we just talked about some of
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the applications of cryptography.
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Don't forget pain, privacy,
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authenticity, integrity, and non-repudiation.
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Then also leading into our next section,
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start with plain text using the initialization vector,
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an algorithm and a key to get ciphertext.
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