Cryptography Introduction and Services
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Video Transcription
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>> In this section, we'll start to talk
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>> about cryptography.
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>> I think cryptography is really interesting,
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but it's also a topic that people get nervous about.
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But if you take it step-by-step,
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bit-by-bit, you'll find that cryptography makes sense.
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You may have to hear some of it multiple times.
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I think the questions you find on the test for
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cryptography are
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actually more straightforward than others.
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I hope cryptography will click for you.
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Even if it doesn't the first time, stick with it.
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The beauty of these videos is that
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you can play them multiple times.
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Now, we'll start talking about the basics.
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I tried to teach this topic as though
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my students have absolutely no experience with it.
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Now, I know some of you may have experience with it,
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but I find a lot of people only know
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the parts that they'd been exposed to,
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and maybe they don't have
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the full foundational understanding.
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We're going to start right at the beginning
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and define some of these terms:
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algorithms, keys, initialization vectors,
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seeds, and salts,
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and what they mean, and how they help
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us protect sensitive info.
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From there, we will build on those ideas and look at
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practical implementations through
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symmetric and asymmetric cryptography.
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There's two ways to provide obfuscation for our data,
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which means making our data unreadable.
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But each of them have different methods
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and different purposes, so we need to understand
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>> the difference between those.
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>> Then just like many other things,
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the best is right there in the middle.
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If we take the good things about
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>> symmetric cryptography and combine them
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>> with the good things about asymmetric cryptography,
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>> we have a hybrid cryptography,
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which is what most applications
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>> and secure protocols use.
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>> Then we're going to move on to talking about integrity.
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One of the ways we get integrity is through hashing.
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Hashing will create a digital representation of a file.
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You can also take that hash and add
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authenticity to it and get non-repudiation.
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Non-repudiation is a combination of
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authenticity and integrity together.
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If we think about that with an email,
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the sender can't dispute having sent
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the message nor the content of the message.
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Then you'll find out that a hash is very limited.
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A public key infrastructure is
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needed to support non-repudiation.
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That takes a lot of support.
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We may decide to use message authentication codes
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or MACs to solve the problem instead.
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MACs provide more security than hash.
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You don't require as much support
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and infrastructure as non-repudiation.
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Now, Mac is one of
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the most fun acronyms that is going
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to mean something different every day.
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But for this module,
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the meaning is message authentication code.
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Last but not least, we're going to
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talk about some email cryptosystems.
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We'll talk about PGP,
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which is proprietary cryptosystem.
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Then we'll talk about S/MIME.
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This is a long chapter and I
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hope you find it as interesting as I do.
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Now, starting with the basics as promised,
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the first thing I want to talk about is
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what cryptography does for us.
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Most people would say that we need cryptography
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because we need privacy and
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>> we want to protect our data.
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>> But in addition to privacy,
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we also get authenticity, integrity,
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>> and non-repudiation.
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>> Here's a quick overview of
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the services that cryptography provides.
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Privacy: Prevents
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unauthorized disclosure of information.
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Authenticity: Verifies the claimed identity.
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Integrity: Detects modification of corruption.
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Non-repudiation: Combines authenticity and integrity.
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A sender can't dispute having sent
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a message nor its contents.
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If in doubt and you can't think of
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all the services that cryptography provides,
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think of PAIN: privacy,
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authenticity, integrity, non-repudiation.
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