1
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So if we go back to our program now, here, you can see we are using four six year staff in the range

2
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line of the afine cipher, Dumbledore's symbolistic the double multiplied by two, OK.

3
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So in this, if you know that there are almost a length of the finci for the simplest possible integers

4
00:00:22,140 --> 00:00:28,680
for key and the length of a finci for the model, Symbolistic returns as a possible integer for Key

5
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Beevor.

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Now to get the entire range of the possible keys, we multiply these values together because we are

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multiplying the same value by itself.

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We can use the double exponential operator in explanation length in the package of fine for the model

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00:00:43,890 --> 00:00:45,470
symbol double multiplied two.

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Now after that we call the gatekeeper function over here.

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If you look at.

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And that we have used in our finci for them now to split a single individual into two individuals.

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So in this example, we're using a function to get even part of VR testing.

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Now, Ricola, the return value of this function call is a couple of the integers, one for A1 and one

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for B1.

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So here then we are storing the value of the Dupas first integer in A1 by placing it.

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That is zero, which is the first of the values.

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OK, so for example, if we say a fine site for the model gatekeeper's jarring bracket ATSDR zero,

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it evaluates to the tuple of the index.

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So 42 to zero, which is divided into 42, the value of the index zero.

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00:01:40,080 --> 00:01:47,220
So this just gets the key A1 part of the return value and stores that in the variable give and key one

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part is ignored because we don't need we want to calculate whether even as valid now for the afine cipher.

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00:01:54,810 --> 00:01:58,770
And if it does not, the program continues for the next key to trial.

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00:01:59,100 --> 00:02:03,930
Now to understand how the execution moves back to the start of the loop, you need to learn about the

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00:02:03,930 --> 00:02:09,330
continuous succumbing to the continuous statement, which is basically using the continual key word

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by itself.

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And it takes no parameter.

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We use a continuous statement inside of a loop, and when a continuous statement executes a program,

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execution immediately jumps from the start of the loop for the next iteration.

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Now, this also happens when the program execution's reaches the end of the loops block.

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What a continuous statement makes the program execution jump back to the start of the loop before it

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reaches the end of the loop.

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Now look at more about this continuous statement.

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Let's go back here in the interactive shell.

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And here we would create say, for Ivan in the range, say three.

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OK, here we are seeing print command for Ivan.

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We are giving here a print see by.

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00:02:59,730 --> 00:03:02,470
So he'll never get zero by one python to Python.

39
00:03:02,850 --> 00:03:10,740
Now, in this case, the for loop loop through the range object and the value in Iven becomes each integer

40
00:03:10,740 --> 00:03:13,270
from zero, but not including three.

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So on each iteration, it will print Python function calls display Python on the screen.

42
00:03:19,440 --> 00:03:25,320
Now contrast that for a loop with the next example, which we will see, except it has a continuous

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statement before the print.

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So over here we would write down again, say for Iven in range, three remains, same print.

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Even here we see continue.

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00:03:38,220 --> 00:03:40,020
Then we give print.

47
00:03:43,150 --> 00:03:44,770
S. Biton.

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OK, and now we end it, so now we get just zero one and two Prender, notice that Bipin never gets

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00:03:53,350 --> 00:03:59,020
printed because the continual statement causes a problem execution to jump back to the start of the

50
00:03:59,020 --> 00:04:01,210
for loop for the next iteration.

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And the execution never reaches the print python line.

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00:04:05,140 --> 00:04:11,080
The continual statement is often placed inside, and if statements look so that the execution continues

53
00:04:11,080 --> 00:04:13,600
at the beginning of the loop under certain conditions.

54
00:04:14,050 --> 00:04:19,660
Now let us return to our call and see how it uses the continual statement to skip execution, depending

55
00:04:19,660 --> 00:04:20,620
on the key.

56
00:04:21,100 --> 00:04:28,990
So if we go back to our demo in this old school, you have seen that we are using the GCD function in

57
00:04:28,990 --> 00:04:33,990
the Cryptome at one module to determine whether Key even is relatively primed with the symbols set.

58
00:04:34,660 --> 00:04:39,610
Now, recall that two numbers are relatively bright if there is one.

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00:04:39,880 --> 00:04:45,610
So if GI, A1 and the symbols that size are not relatively prime, the condition on this particular

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00:04:45,610 --> 00:04:48,900
line is true and the continual statement executes.

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00:04:48,920 --> 00:04:54,130
Now this causes the program execution to jump back to the start of the loop for the next iteration.

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00:04:54,520 --> 00:05:01,930
So as a result of this, the program skips the call to the decrypt method Asgeir function if the key

63
00:05:01,930 --> 00:05:06,400
is invalid and continues to try another key until it finds the right one.

64
00:05:06,850 --> 00:05:12,670
Now, when the program finds the right message is decrypted by calling the decrypt message Istria with

65
00:05:12,670 --> 00:05:18,030
the key on the given line over here where we are passing the key and the message.

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00:05:18,120 --> 00:05:24,730
OK, now, if Silent Mode was set to force the right key messages printed on the screen, but if it

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00:05:24,730 --> 00:05:27,400
was said to true print, call is skipped.

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00:05:27,730 --> 00:05:30,940
Next, we use the is English a function over here?

69
00:05:31,270 --> 00:05:38,710
And we check from the other file that the English module to check whether the decrypted message is recognized

70
00:05:38,710 --> 00:05:39,390
as English.

71
00:05:39,940 --> 00:05:46,270
So if a wrong decryption key was used, the decrypted message would look like a random characters and

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00:05:46,270 --> 00:05:48,790
this is English check would return false.

73
00:05:49,120 --> 00:05:55,350
But if the decrypted message is recognized as readable English, the program displays it to the user.

74
00:05:55,570 --> 00:06:01,580
So we are displaying a snippet of the decrypted message that is recognized as English because is English

75
00:06:01,580 --> 00:06:06,950
check function might mistakenly identify text as English, even though it hasn't found the correct.

76
00:06:07,390 --> 00:06:13,570
So if the user decides that they are indeed the correct description, they can type D or they can press.

77
00:06:13,590 --> 00:06:17,180
And so we are giving those options over here for the user.

78
00:06:17,560 --> 00:06:24,430
Otherwise, the user just press enter to return to the blank screen or string from the input call and

79
00:06:24,430 --> 00:06:30,220
they have find again continues trying merkies not from the indentation of the beginning.

80
00:06:30,220 --> 00:06:35,200
We can see that we have executed the for loop which has completed over here.

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00:06:35,950 --> 00:06:43,810
When we use this written statement, do this, the for loop is still continuing, so the for loop finishes

82
00:06:43,810 --> 00:06:45,550
and reaches this return line.

83
00:06:45,850 --> 00:06:51,200
Then it has gone through every possible decryption key without finding the correct one.

84
00:06:51,460 --> 00:06:58,870
So at this point, the Hackel a fine function returns the non-value to this signal that it was unsuccessful

85
00:06:58,870 --> 00:07:00,230
attacking the ciphertext.

86
00:07:00,550 --> 00:07:06,280
Now if the program had found the correct execution would have previously returned from the function

87
00:07:06,460 --> 00:07:09,440
I never reached until this written statement over here.

88
00:07:09,790 --> 00:07:12,490
Now, after this written statement, what are we doing?

89
00:07:12,490 --> 00:07:13,750
Is as normal.

90
00:07:13,840 --> 00:07:20,440
We are running the program with the special underscore, underscore name, underscore variable that

91
00:07:20,440 --> 00:07:24,590
will be set to the string mean instead of the program name.

92
00:07:24,670 --> 00:07:26,870
So in this case, we call the main function.

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00:07:27,130 --> 00:07:31,000
So that is how we conclude the Afine Saiful hacking program.

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00:07:31,360 --> 00:07:32,260
Thank you very much.