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So welcome to the final part of the program where

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we are going to create the main user interaction.

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We're going to provide the user with four different options.

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Maybe they would like to generate a key encrypted file, the crypto file,

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maybe even just exit.

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And then depending on which option they choose, we are going to have to do something.

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So let's begin.

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All right. So I'm going to say,

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define main. This will be the main, the name of our

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interface

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and let us print out a general welcome message. This isn't necessary.

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But hey, let's just do that. Welcome to the encryption decryption tool.

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OK?

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OK.

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Now we're gonna create the while loop that's going to go through

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the four options. I'm gonna say while and now true

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call on

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and now let us print out the state

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the options. OK? So I'm gonna go print

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and now number one generates

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and encryption

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key.

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OK?

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And now let's go with option number two, which would be to simply encrypt,

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encrypt, a file.

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Uh Option number three

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will be what's

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decrypts

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file.

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And now the final option,

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which is the most boring option,

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exit the program.

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OK?

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There it is. Now,

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since we've,

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since we now have the four options, let us prompt the user

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to provide us with which option they would like to go with.

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So I'm gonna come over here right now and let's go with the variable option.

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So I'm gonna say option

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and our equals and our input. So let's prompt the user to tell us

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what

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option

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would you like to go with? Question mark? OK.

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So let's ask the user, hey, what would you like to do

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now? We'll have to create the el statements for each particular option. So

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let us go

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with the first one in here. So I'm gonna say if

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the option

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is equal to one,

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what do we want to do?

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Very simply, we can generate our key so I can come over here right now and simply say

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generate

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underscore key. And now in brackets, what's the name of the key

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that is encryption

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underscore key

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dot key.

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So we can run the function immediately, right? And this will work perfectly fine.

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However,

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I want to show you something this isn't necessary.

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But what if we wanted to provide the user

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with the option of actually using their own custom key

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and not just the default key that we've already created.

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So we give the user two options.

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You can either use the default key which we already have or

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you can provide us with the path to your own encryption key.

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Now, how would we do this? Well,

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I've already written the line right here.

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So let me just grab this cut,

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gonna come down in here and then paste and

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let me explain to you what's happening in here.

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So

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we're gonna have to pass this into the variable file underscore path

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and now input. So let's ask the user that, hey, enter the file path to save the key.

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Now over here where it says default encryption on

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key dot key is still part of the string.

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I am just indicating to the user that hey,

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if you don't provide us with your own custom key, we're going to use the default key,

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which is encryption on the key key.

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Now, this is very important where it says or

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encryption on the key key. Now, right here

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we are telling Python that hey,

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shooting case,

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even though the user has been provided with the option to use their own custom key.

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If they want to use our own default key,

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then use it. So here we said

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all

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and now the name of a default key.

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So all we need to do right here is just to remove

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the default option

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and then simply pass in the file underscore path

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and there you go. So that's option number one,

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all laid out.

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Let's move on to option number two.

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I'm going to come in here

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and say if

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choice

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equals

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two

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call on.

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So in here

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we would like to encrypt the file.

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Now, remember to encrypt the file, we need three parameters.

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First of all, we need to ask the user to tell us

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the file, they would like to encrypt which will be the input file.

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And then also

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we would like to store the encrypted content.

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What's going to be the name of the output file?

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And then third, which key would they like to use to do the encryption? So

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I'm gonna come over here right now.

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Let's pass the variable input underscore choice. Oh

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Do forgive me. It should be

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if option,

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not choice, I got carried away. Option, not choice. So

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input

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uh

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input file

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to forgive me, input underscore file.

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I'm gonna say equals

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and now let us prompt the user to tell us

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what's the name of the file. So I'm gonna say enter the path of the file to encrypt,

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let me remove this message. So

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enter the path of the file to encrypt. OK? So let's prompt the user to do that

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and then

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outputs

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underscore file is going to be equal to input. And now let us prompt the user to tell us

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the name of the Apple. First, I'm gonna say enter the name

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of the

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of the output file

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call on.

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And now finally, what about the key?

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So I'm gonna say key underscore path,

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OK? It's going to be equal to input

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and now

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we can say enter the path

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of the encryption

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uh encryption key.

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Otherwise

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the defaults

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will be used.

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OK?

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So I'm going to simplify the string statement in here.

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I'm not going to indicate the name of the default K. I don't think that's necessary.

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So all we have to do at this point right now is just to also say the or

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encryption

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uh underscore key,

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the key

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and there you go. Alright. So

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one thing we need to do right here is we need to account for errors.

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OK? What if the user, what if maybe they provided the wrong input file

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or the name of the output file is incorrect or maybe even the key

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isn't correct?

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What should happen? So let us provide the option right now to cater for that.

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So I'm gonna say try

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remember that. And now

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key

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equals load underscore key

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and now in brackets

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the key path,

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OK? And now

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the most important parts encrypt

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underscore file

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and now in brackets, what are the three parameters?

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We have the input underscore file, we have the output

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underscore file

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and now we have the key as well. So these are the three parameters

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and if there's any

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error, let us generate. So I'm gonna say except

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Exception,

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OK?

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As E

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and now we can print

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our error message. So I'm going to use the F string

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and then I will say something like

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uh during

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encryption,

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OK? Call on and now we can use our call braces to indicate

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what the particular error is. And There you go.

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So we have successfully created option number two with a

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user to provide the path of the file.

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They want to encrypt the name of the output file and then also the key as well.

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And we've also added some error handling. Fantastic.

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Now,

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all I'm going to do

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is I'm just gonna grab this block of code

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and I'm simply going to paste it because think about it, the encryption

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and decryption process is almost the exact same thing is just opposite, right? So

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I'm gonna copy all the block of code

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and I'm gonna come over here

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and now I am going to paste it.

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OK?

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Now notice though that the indentation isn't correct. So make sure

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that when you do the exact same thing as I did,

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make sure that your indentation is correct,

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make sure everything is aligned properly and this should be fine. OK?

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All we need to do right now is to change the options in here.

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So option number three to number two

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input file, I'm gonna say enter the path of the file to what to decrypt.

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OK?

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An output file,

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enter the name of the app file, that's fine.

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Enter the path of the encryption key otherwise. OK?

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Keep in mind that the encryption key is the exact same thing as the decryption key.

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So we don't need to change the text in here.

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You could change it if you want to, but I'm just gonna leave it as it is.

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And finally, OK, over here as well, we just need to change this

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and there you go, error handling is intact.

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And one more thing we need to change is going

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to be over here where it says the encrypt file

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over here. It should be a decrypt

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file. OK? So you want to make sure

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that whenever you copy and paste code and you need to alter some text,

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make sure that you go through it properly. Otherwise

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you may end up having some issues.

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Ok?

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All we have to do right now is to add the fourth option. So

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I'm going to come in here and say

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option equals four,

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we can print in

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the program

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and now we're going to have the break statement as well because remember

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that even though we provided four options to the user,

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they might become quite silly and decide to choose option

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number five or six or seven or any other option

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that doesn't even exist. So we need to account for that as well.

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I'm gonna say break and then

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we're going to provide the final else statement

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and now we can simply say print and then

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tell the user,

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please choose a valid option

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and there you go

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and there it is. And now all we got to do is to run

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the main function

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and there it is. So

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hopefully the program should work.

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Uh

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let me go ahead right now and

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run the program.

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And there you go. Ok? So

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let us test this out. I'm gonna go, first of all with option number one

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press enter,

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I'm gonna go with the default. So I'm gonna press enter again

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and there you go. Awesome.

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So you can see right now we do have the encryption key that's been created

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by the program.

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So now let us try to encrypt a file.

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So I'm gonna come over here right now and let's create a sample

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dot TXT file. Let's add some text in here. This is some sample text

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which we are going to encrypt

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and also decrypt.

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OK? So let's see. I'm gonna go ahead right now and go to the program.

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Let's go with option number two right now.

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So let us try to encrypt our sample

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dot TXT file.

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I'm gonna press enter

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and now what's going to be the name of the output file. Let's call this the encrypted

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underscore file dot TXT.

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Let's go. We're gonna use the default key. So I'm gonna press enter

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and there you go. So let's take a look. We have the encrypted underscore

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FDO TXT

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00:13:00,270 --> 00:13:02,780
and there it is, this is the encrypted version

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of our sample text file. So now let us try to decrypt the encrypted file

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and see if we'll get back the same text. I'm gonna go with option number three,

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enter the path of the file to decrypt is going to be encrypted

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underscore file

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dot TXT.

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And that will be the name of the

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output file. We can call it decrypted

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underscore file

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dot TXT.

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We're gonna go with the default key

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and the 0000, I'm sorry. We have an error message that says

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no such file. The director encrypted

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file dot TXT. What did I do wrong?

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Uh We do have, oh.

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Hm.

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Do you see what I did?

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My file is called encrypted, not encrypted.

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I do apologize. I need to get myself a new pair of glasses.

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I do apologize.

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Let's try one of that again. So option number three.

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So the file here is encrypted

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uh underscore file dot TXT.

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And now the name of the output file,

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I'm gonna go with decrypted

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and let's go file

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dot txt

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default key and there you go. Ok. So now let's take a look at the decrypted file

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and there you can see it work.

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So first of all, we encrypted sample dot TXT.

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We got our encrypted file which you can see right now and then we decrypted this file

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to get back the exact same text. So you can see right now it works perfectly fine.

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Let's try option number four to exit the program. Ok. It exited the program.

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Let's run the program one more time and let's go with option number seven.

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And it says please choose a valid option and there you go. So

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well,

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we successfully created ourselves an encryption and decryption tool.

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It's been quite a lot. But hopefully

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you've learned some new concepts such as using the

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right binary and read binary modes.

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You've also learned how you can provide the option

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for the user to use their own custom key or

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use the default key.

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And hopefully you learned a lot in this money project.

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Thank you so much for watching and of course, I will see you in the next class.