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- Let's go over what
are hashing algorithms.

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And before we do that, let's
see what is actually hashing.

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So hashing is a method used to
verify data integrity, right?

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That means that you can verify
the integrity of a file.

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You can verify the integrity of

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data being exchanged between two entities,

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or you can verify the integrity

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of a process or a program, right?

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A cryptographic hash function is a process

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that actually takes a block of data.

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And then it creates a small
fixed size hash values, right?

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It's a one way function.

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That means that actually

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if two different computers
take the same data

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and run the same hash function

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they should get the same
fixed size hash value.

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For example, you know,
perhaps a 12 bit long hash

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and I'll demo this in a few minutes.

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Now, examples of hashing algorithms are

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the Message digest 5 or MD5

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which actually creates 128 bit digest.

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And it's actually less secure

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than the ones below the secure
hash algorithm or SHA-1.

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It actually creates 160 bit digest.

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And then the more secure is
the second version of that

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which is a secure hash
algorithm or SHA version two

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which actually include digest
between 224 bits and 512 bits.

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So in this example, I actually
have three files, right?

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File one, file two, and file three.

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And as a matter of fact, if
you actually see, you know

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file one in this case
actually has the same bites.

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That's five, three.

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So it's 32 of the sites.

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And as a matter of fact.

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If we do a LS minus H to do
a human oops LS minus L and H

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you can see actually 32 bites

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in each and then file two has 288 bites.

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If we actually look at each of the files.

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So let's look at file one, for example

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the file context is, you know,
is just self explanatory.

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This is the contents of the file.

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That's what is actually in that file.

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If you look at file two,
the contents of the file

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this is actually this and you, if you see

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there's actually more data subsequently

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you see the number of
bites actually increase.

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Now, this is the
particular fashioning here.

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File three is name file three.

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However, if I open that file,

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you will see that the content

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is exactly the same as file one.

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As a matter of fact, what
I did before is demo is

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I actually copy file one to file three.

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Now let's actually take a look
at the actual hashing, right?

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So how to verify the
integrity of those files

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and you can actually have
most operating system

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actually support a hashing verification.

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In this case, I'm actually
running on the Mac OSS device.

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This is very similar to a
Linux environment as well.

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And there's a shasum utility, right?

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That you can actually use.

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And so matter of fact

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I'm actually just gonna
do the help in here.

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And basically it prints or checks

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the check sums of a file
or, you know, a binary.

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And in this case

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I'm actually gonna use
the 512 option of a SHA-2.

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So let's do this real quick

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shasum minus A for algorithm, and then 512

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I'm gonna do it through all
the files in these directories.

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So doing a wild card

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and here you actually
see the different hashes

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for each of the files.

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So if you look at,
remember that the contents

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of file one and file three were the same.

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You actually see that
the shasum calculated

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or the hash sum calculated
that is actually done in here.

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And hexadecimal code in here

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is exactly the same as file three, right?

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So again, file two was actually different

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and subsequently you actually
see it as a different

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a different output here.

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So this is actually very important to know

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especially whenever you're
actually doing file integrity

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and file verification and, you know,

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any other type of verification
using hashing algorithms.

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And here, actually, I want to summarize

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what you learned in the, in this lesson

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and in the previous lesson, right?

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So encryption algorithms
and hashing algorithms

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and what they're actually used for, right.

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So first starting from the left

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and the top left symmetrical
encryption algorithms

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remember that they
actually use the same key

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for encrypting and decrypting data.

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And these are some of the
examples of those algorithms.

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Then you have asymmetrical
encryption algorithms

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which use a public or private key, right?

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So one key to encrypt data
and another one actually used

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to decrypt and some examples
of those algorithms.

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Then we actually cover as well,
digital signatures, right?

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So this is actually
done for the encryption

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of a hash using a private
key, and then the decryption

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of a hash using the senders public key.

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As we actually saw in the
previous examples of PGP, right?

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Also you have the
Diffie-Helman Key Exchange.

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And you know, of course
the examples using IP sec

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and encryption algorithms
and hashing algorithms using

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use for confidentiality, integrity

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and authentication, right?

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So here, you know, self explanatory,

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some encryption algorithms that provide

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converting clear text to cipher texts,

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increase the ability for you to actually

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protect the confidentiality of you know,

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transactions and files.

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And these are some of the examples

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of the encryption algorithms to do that.

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And then for data integrity
or for file integrity

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which validates the data
by compared hash values

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just like we saw in the demo

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these are the algorithms
that actually are supported.

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And then of course you
actually have algorithms

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for authentication and to
verify the peers identity.