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To round up this section on libraries and modules.

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I need to show you how you can work with an external library.

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And the one we're going to be working with is going to be a very,

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very powerful library and it's going to be the Cryptography

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library. And in fact, let me drag over the documentation.

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So this particular library is developed and maintained by the Python community.

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You can go to Cryptography dot I or if you want to learn more.

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But right here, they provide

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us with ideas on how to actually import

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the library and specifically

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a particular function, which is the

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fernet function. OK. This is what is mostly used for

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encrypting and also decrypting messages.

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So

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let me show you

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how we're going to work with it.

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And I've added some notes in here because it's

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very important for you to understand step by step

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how our program is actually going to work. Because to be honest,

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it can get quite confusing. OK? I'm not gonna lie.

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Remember that in encryption,

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we can encrypt a key.

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All right, we're going to use a cipher that we can then use to encrypt our key.

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But then we can also decrypt the message that has been encrypted.

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So

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the way it works is that first of all,

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by using the F

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function, we'll have to generate the key

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that we're going to use for both encrypting and decrypting.

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And then we can pass that key to our cipher.

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Remember in the world of encryption, we're gonna use ciphers

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that combines an algorithm

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and a key for the actual encryption and decryption. So it's basically four steps.

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First of all, we generate our key.

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So we say

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to generate key, this will generate the key

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and then we can pass the key to a cipher

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and now to encrypt the actual message,

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we will say cipher because now it's holding the key and then dot encrypt

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and then in brackets are function message dot encode

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and then the opposite to decrypt,

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we can say decrypted message would be equal to cipher dot decrypt.

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And now in brackets because we're decrypted what the encrypted message.

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So we're gonna pass that in

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and then add the last method dot decode

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to decrypt

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a message.

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So

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let us start from the very beginning. OK.

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The first thing I'm gonna do

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is to import, so I'm gonna say from

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clip to

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graph

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feed

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dot

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fernet,

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we're going to import

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the class of fernet.

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OK?

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That's the very first step.

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Now step one remember is to generate the key.

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So I'm gonna say key

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equals

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and now fer

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generate underscore key.

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This will create a

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key

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and now we can say cipher

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will be equal to

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fernet

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and then key.

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At this point in time, I would like us to first of all print

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the generated key that we've created. So

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I can come in here right now and say print and then in brackets,

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let's say uh generated key. OK. So J

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narrated

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and then key

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and add my colon

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and then a comma

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and then key

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dot

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the code.

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All right.

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So this right here, this particular function here is what we're going to use

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to show the key as a string.

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Now,

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next step will be to actually encrypt the message.

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So what do we do?

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We can say message

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equals, let's add

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the message. The default here says hello world.

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Uh Let's make it a bit more complex. I'm gonna say hello world.

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This is a circuit message. OK? I think this is fine. This is a circuit message. OK? So

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this is the message

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they were going to first of all encrypt and then decrypt. So

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I will now come in here right now and say encrypted

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on this call message.

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Now we're going to encrypt the message and how we're going to do that.

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We are going to say cipher

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dot encrypt. And then

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in brackets, we're gonna pass the message

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and the method dot encode to encrypt a

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message

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so far. So good.

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Next step

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will now be to print,

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we can print the encrypted message right now. So I'm gonna print in brackets,

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let's add our codes and then I can say,

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uh, encrypted

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message

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is colon and now

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add my comma

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and then simply

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say encrypted underscore

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message.

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OK.

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So far so good.

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The last step, of course, after encryption will be to decrypt.

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So I'm gonna say decrypted

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underscore message

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equals to what

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cipher

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dot decrypt.

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And then in brackets, we're going to pass in what the encrypted

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and crypted

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underscore message.

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And then

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dot

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the code

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brackets

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close the last bracket

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and there it is.

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So last step right now will just be to print

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decrypted message is and then

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decrypted

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message. Now I can see here we do have, oh, there is no closing bracket to forgive me.

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I made a mistake right there

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and hopefully this should work.

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Let me go ahead right now and run

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and there you go.

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So right now you can see on my screen, it says loading the next environment.

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So the beauty about

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Python when working

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is that

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even though this is actually an external library

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is going to automatically import the library for.

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So it's basically installed the library

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and now we have the program running and it says

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the generated key. Was this ok? That's a long key.

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So the encrypted message is now this right here

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very, very long as you can see.

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And of course, the decrypted message is hello world, this is a secret message.

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Let's try changing the message to something else.

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And I'm gonna say, Python is amazing.

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Let's run it again

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and there you go. So now we have a different generated key and of course, a different

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encrypted message. So

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that's how to work with the Cryptography

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library. And just to kind of give you a quick recap. Once again. First of all,

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we imported the module fernet

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from the library of Cryptography.

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And then of course, in the world of Cryptography,

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we're gonna have a key that we use for encryption and decryption.

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We generated the key right here with the use of the

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generate key method.

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And then we assign the key to our

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cipher.

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We printed out the generated key by making use of the key to decode function

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and then

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to encrypt the message we have to, first of all add what the message actually is.

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The message here is Python is amazing.

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And then we say, OK, encrypted message will be equal to now the function cipher

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encrypt

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and then in brackets message dot encode.

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So the encode method right here

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will convert the plain text or our string into bytes.

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OK?

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And now the cipher

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encrypt will take the encoded message,

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it will then encrypt it producing an encrypted version.

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And of course, the output will be equal to the encrypted underscore message.

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And then the last step right now is to actually decrypt the message. So

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cipher dot decrypt right here,

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we'll take the encrypted message and then decrypt it,

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we turn it back to the original format

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and then the dot decode right here. Then this method

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will convert the decrypted bytes

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back into a readable string format.

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And of course, finally, we printed out the actual uh decrypted message.

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So

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that's it. Thank you for watching the video. I will see you in the next class.