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OK, so really quickly, let's talk about cryptography a little bit just for a lot of you guys, you

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might be looking into getting like you, S.H., or your security.

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Plus, understanding cryptography in a different attacks against it will be very important.

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So to sum it up, cryptography, by definition is a science or a study of protecting information, whether

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it's in transit or arrest.

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And this is typically done by using techniques to render the information unusable to anyone who does

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not possess the means to decrypt it.

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So in our case, it simply means taking a text like Hello John, and transforming it into something

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that's unreadable like this this string right here that I'm not even going to try to read.

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And this is just to keep the contents of the message confidential.

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And this is achieved using what are called encryption algorithms.

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So encryption algorithms are pretty much just mathematical formulas, and they can encrypt and decrypt

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data using keys without the key, the message will be forever unreadable for the most part and will

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not be able to be decrypted.

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And there's two forms of encryption.

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There's some magic encryption and there's asymmetric encryption.

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So symmetric encryption is when you use the exact same key to encrypt the data in the exact same key

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to decrypt it.

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So this provides confidentiality, but not but not not repudiation.

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And one of the challenges with symmetric encryption is that you have to have some way, some secure

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way to transfer the key to whoever the recipient of your data is so that that's where it kind of causes

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issues and only it should only be used in certain situations.

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Asymmetric encryption, on the other hand, uses one key to encrypt it by encrypt the data and then

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another key to decrypt the data.

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And typically the recipient of like a message or something, they're there publicly, which is a key

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that anyone can get access to, is used to encrypt the data that you know, that they're being sent.

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And then their private key is the only key that that can actually decrypt that data.

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So really, as long as the private keys is private, you know, no one can read that except for them.

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So that's where how asymmetric encryption is useful and very versatile.

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So there are some there are things called ciphers and ciphers are the methods by which the data is actually

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encrypted.

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So there's two different kinds of block ciphers and string ciphers.

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So extreme ciphers, bits of data are encrypted as a continuous stream.

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So you can just imagine like feeding something into a machine and it goes in one end and it's going

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out the other end encrypted.

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And this is typically a lot faster than block ciphers.

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So for block ciphers, bits of data that are put into blocks.

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So, for example, you'll see that some ciphers use, you know, 64 bit blocks and they're encrypted

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all at once with a key in an algorithm.

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And this causes slower speed for encryption.

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But, you know, a little bit more reliable and a little bit more secure in some ways.

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So as a result, you know, the cipher is, like I said, are used for specific functions based on how

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they work.

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So reliability and speed for the most part.

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So just to go over quickly, some popular symmetric encryption algorithms that you guys want to be aware

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of, the D and three D, which is also called a triple test.

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So this is a data standard and it's a block cipher that uses a 56 Beaky and it reserves eight bits for

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parity.

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So this was the de facto standard, for the most part, more then, as came along, the advanced encryption

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standard and is also a block cipher.

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And it uses either one hundred twenty bit, one hundred ninety two or two hundred fifty six big keys.

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And like I said, it replace deaths and triple this.

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And just also for clarity, triple das is just doing the deciphering on data three times as all that

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is.

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So the next one is going to be to fish the of the popular blog Cypher, and he uses a key size of the

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256 bits and then there's blowfish, which is faster block cipher.

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It uses a 64 bit block size and a key that ranges from thirty two to four hundred forty eight minutes.

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And then news RC, which is reverse cipher.

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And this is the block cipher that uses a variable chelate of up to 20 and 40 bits.

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And the latest one, which is RC six, uses one hundred twenty eight bit blocks for encryption.

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So what I want you guys to get from this is pretty much know these names, know that these are block

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ciphers and know, you know, how many bits are used like he was.

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OK, that's what you're going to need to know, especially if you're going for these certifications.

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So some asymmetric encryption algorithms that are popular, Willhelm and this is pretty much what you

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see a lot is a secure key exchange protocol.

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And he uses SSL and IPCA encryption actually to Shirkey so the keys can be exchanged in a secure manner.

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Elliptical curve crypto system.

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Also you'll see in places it uses points.

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It's very complicated, very complex is points on an elliptical curve in conjunction with logarithmic

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problems for encryption is integers.

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So it uses like a lot less processing power than other methods.

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So it's very popularly used on mobile devices.

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So if you ever see, like, you know, particularly exam's or something and you see something about

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encryption for a mobile device, this is probably the answer.

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And then there's RSA and this proves that she's strong encryption through the use of, you know, large

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prime numbers.

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And factoring these numbers creates key sizes of the four thousand ninety six bits.

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This is the standard.

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Typically when you creped things, you're going to be using RSA like for the most part you can use like

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RSA.

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Yes.

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This is what you're going to be doing.

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OK, so now let's go over some hashing algorithms so hashing algorithms can be thought of as forms of

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encryption, but you just can't reverse them.

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It's a one way transaction.

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So as a result, you know, hashes using hashes that you might have heard of a file hash or something.

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And this is a good way to ensure that the integrity of files and messages remain intact.

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And you typically would use hash tag algorithms to securely transmit things like passwords like you

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would never send or store passwords in plain text.

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You would you once you hash it and then either store it or send it somewhere, that's what you want

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to do.

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And if you're going to check that again, it's like another password, like maybe in a form like online,

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you would take the hash of whatever for whatever password or submit it, send it over, compare it to

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the hash and then see then give like a confirmation of if it's correct, if it's correct, and do whatever

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function that form is supposed to do.

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That's like the secure way of doing things.

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And that's kind of like we're hashing algorithms are mainly used.

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So just some specific hashing algorithms that you guys should know of this MI five, this produces a

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one hundred twenty bit hash output and is expressed as a thirty two digit hexadecimal number.

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There is one which is very popular, very popular to use for most products, like the probably the widest

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use.

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It produces a one hundred sixty bid value output.

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So if you, if you get this sha one hash of, of like a file or something is going to be a one hundred

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and sixty bid value and then you shot two and three shots, it holds four separate hash function functions

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that could produce outputs of two hundred twenty four, two hundred fifty six, three hundred eighty

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four and five hundred four bits just to put it out there to Shazza isn't very isn't as widely used as

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one.

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So you know, further progressing like progress on this stuff is kind of like slow down a little because

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I want to still use a lot in Shazza has a lot of functionality and a lot of potential, but one day

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I'll probably be up there and probably the most widely used just because of what it can do in the range

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of hashes then it can actually have.

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OK, so while hashes are secure, you can't attack them so they're not immune to being attacked at all.

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Hashes can't be cracked quote unquote in various ways, including preparing like a discovered hash,

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like maybe someone pulls a hash out from a database.

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They can compare that hash to the hashes of a list of strings that they have in a file.

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And this is achievable pretty easily, pretty quickly with applications like Hash Cat and John and Linux

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are you're going to see that.

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And then also hash is also vulnerable to what are known as collisions.

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And this is when the hash of two separate strings actually are equivalent by some crazy coincidence.

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This is a very small chance of this happening, but it is always possible.

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So in order to protect hashes, there's an extra measure.

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That extra security measure is called a salt.

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And you can add this on to a password hash, and this is called sorting a hash.

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So this is when you add just extra bits of data, you know, onto a hash to prevent the original hash

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from being cracked.

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And if further reduces the chance that the plaintext version of whatever that original, you know,

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whatever the original plaintext string was, it's going to prevent it from being uncovered.

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So sorting hashes is very common nowadays, but sorting hashes doesn't always solve the issue, because

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if I had if assault is detected, these applications like John and Hash Cat can actually figure out

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what the source is and still be able to correct hash.

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So that's something that, you know, to keep in mind when you're thinking about attacking.

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Cryptography is not extremely practical and it's not something that, you know, we're going to be able

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to do here.

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And that's something that's actually commonly done.

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There's a few ways that it can be hacked, though.

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So we're going to go over those.

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So there's three ways right now.

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Of course, there's a couple other ones.

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But the three main ways are going to be a known plaintext attack, a ciphertext only attack and a replay

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attack where the replay attack is probably going to be the most effective one for you.

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So the no plain text attack is when the attacker has both ciphertext and a plain text and uses uses

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both in to kind of figure out how it was encrypted, that it would analyze and see what's going on and

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try to see, hey, maybe this was the key that was used in this data.

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Now I can use that key, you know, to, you know, send out specific messages or something like that.

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I'm going to personally somebody or gain access to different data that's being sent across the network

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between like two to something on the side only attack where the hacker has like multiple messages that

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are encrypted, like in the same exact way.

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And then it would do a statistical analysis on it and figure out, you know, exactly how they were

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encrypted.

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So this was probably a little bit more difficult versus the first one.

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And it's in even both.

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It is a very kind of impractical to do for the most part and then is a replay.

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It's like this is your best bet as an ethical hacker.

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This is typically done with like a man in the middle of attack where the attacker would you be.

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You you sit in between two computers or two or something like that, and you capture a cryptographic

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exchange and then you repeat it, you know, in hopes of gaining access to whatever, you know, the

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host is trying to, you know, gain access to.

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And, you know, this is typically is not to affect them when session.

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So I use.

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But there are ways and still session to still like people's sessions and cookies and such, which we're

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going to go over.

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We're also going to go over a method of actually being able to spoof someone and downgrade like it would

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typically be a GPS.

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If they visit a site, we can actually make them we can actually spoof them and make them think that

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they're still visiting a cyber really they're visiting our machine.

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And then that way they're not using https.

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So that's that's kind of a way to be cryptography as well.

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So that's a little bit of cryptography.

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Just to teach you guys just a little bit, help you get ready for your exams that you're probably going

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to take.

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And also to give you an idea of how you can actually take, you know, take on cryptography in somewhat

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of a way to give you an idea.

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So typically, like I said, man in the middle of tech is going to be your bread and butter.

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And we're going to kind of do a man in the middle attack here.