1 00:00:00,330 --> 00:00:06,330 So we come here in the eighth part and do that, so after replacing all the parts in the list and give 2 00:00:06,330 --> 00:00:14,190 it the solve letters, the function combines a list of strings into a single string using a joint method 3 00:00:15,150 --> 00:00:17,040 to create a simple substitution. 4 00:00:17,970 --> 00:00:26,160 Now, this string is passed to the decrypt message function of your simple substitution cipher, which 5 00:00:26,160 --> 00:00:27,030 is based here. 6 00:00:27,180 --> 00:00:34,230 Finally, we get the return of the decrypted message string from the decrypt message is your function 7 00:00:34,470 --> 00:00:38,580 and we now have all the functions we need to find an intercepted letter. 8 00:00:38,580 --> 00:00:41,490 Mappings, hackle key decrypt a message. 9 00:00:41,670 --> 00:00:44,730 So let's look at a quick example of how this functions. 10 00:00:44,730 --> 00:00:46,230 Work in the interactive Chente. 11 00:00:46,650 --> 00:00:49,170 So let's come to decrypting in the interactive. 12 00:00:49,170 --> 00:00:51,570 Shall we have done the last part? 13 00:00:51,570 --> 00:00:53,070 Everything in the interactive one. 14 00:00:53,400 --> 00:01:00,600 Now let's return that and we use the particular mode text where we will be using the intersected mapping 15 00:01:00,600 --> 00:01:07,710 variable to create a more olio shell examples or decrypt deciphered message that we had inserted. 16 00:01:08,070 --> 00:01:17,070 So now at this particular point we will have to insert, say, let's go here and we would see our programmers 17 00:01:17,430 --> 00:01:25,560 say, let's go back here to December subhi so simple sub Hackel dot. 18 00:01:25,940 --> 00:01:28,980 Now we will be using the decrypt with. 19 00:01:30,680 --> 00:01:41,800 Saifullah, dumpings, and he'll be able to pass the text, also the intercepted mapping one and the 20 00:01:41,800 --> 00:01:44,890 text that we're going to pass is there already in notepad. 21 00:01:45,190 --> 00:01:52,300 So let us just copy down the text over here in the single quotation marks after this. 22 00:01:53,270 --> 00:01:56,910 Let's get to we are getting it as uncomfortable increases disappoint. 23 00:01:57,100 --> 00:02:03,760 So the ciphertext decrypts to the message as you can see, the decrypt with cipher letter mapping function 24 00:02:03,760 --> 00:02:07,660 Vorkuta perfectly and written a fully decrypted string. 25 00:02:07,990 --> 00:02:14,230 But this example doesn't show how or what happened when we don't have all the letters that appear in 26 00:02:14,230 --> 00:02:20,160 the ciphertext now to see that what happens, we are missing a cipher letter decryption. 27 00:02:20,530 --> 00:02:22,330 Let's remove the solution of the cipher. 28 00:02:22,330 --> 00:02:29,890 Letters emanates from the intersected mappings by using some instructions like we are seeing C intersected 29 00:02:30,730 --> 00:02:31,510 mapping 30 00:02:34,360 --> 00:02:39,250 one at the index M we are making is equal to blank. 31 00:02:39,730 --> 00:02:49,980 Also intercepted mapping one index is also we are making it like. 32 00:02:51,150 --> 00:03:01,590 And then again, we try to do it something like a simple sub Hadco, but we call this again decrypt 33 00:03:02,100 --> 00:03:13,740 with this the text and intercepted mapping one so that this copied all the text here again. 34 00:03:14,460 --> 00:03:19,670 So now you can see you're going to try to decrypt the cipher little with this you're getting there. 35 00:03:19,680 --> 00:03:25,110 But somewhere on the school site on this part, the part of ciphertext wasn't decrypted. 36 00:03:25,240 --> 00:03:29,110 Cipher letters without a decryption letter was replaced with that. 37 00:03:29,130 --> 00:03:34,320 And so this is rather short ciphertext to hack normally encrypted messages. 38 00:03:34,330 --> 00:03:36,240 Much would be much more longer. 39 00:03:36,630 --> 00:03:42,900 So to hack Longmate encryption, you will need to create a cipher letter mapping for each cipher word 40 00:03:42,900 --> 00:03:46,210 in the longer message and then intercept them altogether. 41 00:03:46,650 --> 00:03:52,320 So the hacks and bizarre function calls the other functions are not programmed to do this exactly the 42 00:03:52,320 --> 00:03:54,300 way as we have done it over here. 43 00:03:54,690 --> 00:04:01,440 So with this, let us go to our program and the last part in our program after this Descriptivist Cipher 44 00:04:01,440 --> 00:04:07,830 letter mappings is we are calling the main function to run the program if it's being run directly instead 45 00:04:07,830 --> 00:04:11,820 of being imported as a module by another Python program. 46 00:04:12,300 --> 00:04:17,490 So with this, we have completed our discussion of all the functions that this simple subcortical one 47 00:04:17,490 --> 00:04:20,070 program uses is now. 48 00:04:20,070 --> 00:04:27,290 From this, we must have understood that this is fairly complicated the way we have trying to hack or 49 00:04:27,300 --> 00:04:28,530 substitution Saiful. 50 00:04:28,950 --> 00:04:35,340 OK, you have also learned how to use a cipher letter mapping to model the possible decryption letters 51 00:04:35,340 --> 00:04:36,920 for E ciphertext letters. 52 00:04:37,290 --> 00:04:43,110 You also learn how to narrow down the number of possible keys by adding some potential letters to the 53 00:04:43,110 --> 00:04:48,810 mappings, intercepting them and removing the sort of letters from other list of potential decryption 54 00:04:48,810 --> 00:04:49,320 letters. 55 00:04:49,650 --> 00:04:55,320 So the main advantage of a simple substitution cipher is it's a large number of possibilities. 56 00:04:55,680 --> 00:05:02,790 The disadvantage is that it's relatively easy to compare cipher votes towards a dictionary file to determine 57 00:05:02,790 --> 00:05:05,190 which side Four-Letter decrypt to which letter. 58 00:05:05,440 --> 00:05:13,500 Now, now, in the next session, we would explore a more powerful alphabetic substitution cipher, 59 00:05:13,500 --> 00:05:19,410 which is called less Virginia's Saiful, which was considered impossible to break for several hundred 60 00:05:19,410 --> 00:05:19,870 years. 61 00:05:20,520 --> 00:05:22,880 So that's it from this particular session. 62 00:05:22,980 --> 00:05:28,800 Hope you have understood the program that we have done because there are many programs intersected with 63 00:05:28,800 --> 00:05:31,640 each other for execution of one program. 64 00:05:32,160 --> 00:05:37,320 So all of them you would find it illegal or just some hands on experience on them. 65 00:05:37,590 --> 00:05:41,900 So that makes the concepts very much clearer if you practically do those things. 66 00:05:42,240 --> 00:05:46,600 So we will see in the next session programming the Virginia cipher. 67 00:05:46,860 --> 00:05:48,180 That's it from this session. 68 00:05:48,210 --> 00:05:49,200 Thank you very much.