1
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So now let us understand how many pages of fine cipher have now let us try to calculate the number of

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possible keys.

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The afine cipher has a fine ciphers key V1 is limited to the size of this.

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Envisat with the length of your symbolistic is 66.

5
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So at first glance, it seems like he even would be larger or as large as you want it to be, as long

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as it's relatively plain to the simple set size.

7
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Therefore, you might think that the afine cipher has an infinite number of keys and cannot be brute

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00:00:37,200 --> 00:00:37,610
force.

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00:00:37,860 --> 00:00:39,180
But this is not the case.

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Recall how large keys in this season Saiful end up being the same as monarchies due to the wraparound

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effect.

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So with this implicit size of 66, the key sixty seven in the Caesar cipher would produce the same encrypted

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text as given the afine.

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00:00:58,110 --> 00:01:05,250
Saiful also wrap around in this now because the key be one part of the afine cipher is Seimas.

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You'll see the cipher.

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Its range is limited from one to the size of this implicit not to determine whether the offensive A1

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is also limited will write down a short program to encrypt the message using several different individuals

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key even and see what is the ciphertext look like.

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So we'll open a new file editor and into some code into it.

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Save it with a particular name in the same folder as we had the a fine cipher program created and the

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Cryptome at one fight.

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So let us create your new file.

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Now, in this, the first thing is we would import our.

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A fine.

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Saiful.

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Demo and the diplomat won, and now here we will see the message a SDR is equal to will give you some

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text.

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See, this is as simple as possible, but not simpler, something like that.

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00:02:12,270 --> 00:02:23,280
And we would run for Loop Saiki even in the range we give you say two comma a T, we run.

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This syquia still is equal to A1, multiplied by the length of now here we will use the afine Saiful

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Demel got our Symbolistic plus one.

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Then we check that if say Cryptome at one dot we call the GCD function because they're A1 and the length

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of a fine.

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00:02:58,260 --> 00:03:04,530
So for the Modot Symbolistic that's equal to one.

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Then we give print c p a1 comma the afine cipher demo Daudt.

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We call here the encrypt message still and parse the SDR messages to.

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So we will see if this program in the same location, let us give your CI a. find the demo bought by.

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And if after saving this, let us execute this.

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So cute how many kids it is using any random number of kids now in this particular program that we have

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written, we are importing the afine for demo for the encrypted message function and the crypto math.

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00:04:03,970 --> 00:04:10,850
One module for its function will always encrypt the string stored in the message is still variable.

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So the for loop remains in the range between two to eight because in this case, zero and one are not

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allowed or not allowed as a valid GUI Kansi.

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So an integer as explained earlier.

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00:04:22,660 --> 00:04:29,410
So on each iteration of the loop, we calculate the key from the current one and always uses one for

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00:04:29,410 --> 00:04:36,890
cabi one, which is why one is added at the end of the particular session over here after default.

47
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Now keep in mind that A1 must be relatively primes with a simple set size to be valid.

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So key one is relatively private with the size of the city of the key and the symbol size is equal to

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00:04:49,600 --> 00:04:49,850
one.

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00:04:50,320 --> 00:04:56,230
So if the core of the key and the symbol sets, it is not equal to one, the if condition on this particular

51
00:04:56,230 --> 00:05:00,850
line will fail or will skip the call to encrypt message.

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00:05:01,150 --> 00:05:07,630
So in short, this program prints the same message encrypted with several different integers for which

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00:05:07,630 --> 00:05:09,240
the output we have seen this.

54
00:05:09,670 --> 00:05:11,990
So look carefully at the output.

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00:05:12,010 --> 00:05:19,030
You will notice that the ciphertext, let's say for P1 four five let's see over here is the same as

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00:05:19,030 --> 00:05:22,800
the ciphertext for let's say check it over here.

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00:05:23,500 --> 00:05:25,750
See this one similar to this.

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00:05:25,750 --> 00:05:32,910
Seventy one, OK, in fact ciphertext from seven and seventy three are also C if you look at this see

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00:05:32,920 --> 00:05:35,220
seventy three and see this one.

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00:05:35,890 --> 00:05:36,880
This also all same.

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00:05:37,660 --> 00:05:38,080
Right.

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00:05:38,410 --> 00:05:40,510
And the ciphertext for totin.

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00:05:40,510 --> 00:05:49,210
If you look at this one and you'll see seventy nine, this one is also C so notice that subtracting

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00:05:49,210 --> 00:05:56,470
five from seventy one thousand sixty six size of of a symbol, this is like one of seventy one does

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00:05:56,470 --> 00:05:58,870
the same thing as a one of five.

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00:05:59,350 --> 00:06:04,050
The encrypted output repeat itself or wrap around every six to six keys.

67
00:06:04,300 --> 00:06:10,740
So as you can see the a fine cipher has a same wraparound effect for even as it does for every one.

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00:06:11,140 --> 00:06:14,380
So in some key, Ivana's also limited to the symbols.

69
00:06:15,160 --> 00:06:22,570
Now when you multiply six to six possible keys, A1 keys by six two six possible keys V1, the result

70
00:06:22,570 --> 00:06:25,070
is four, three, five, six possible combinations.

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00:06:25,570 --> 00:06:32,080
Now, when you subtract the individuals that can't be used for a because they are not relatively Prineville

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00:06:32,080 --> 00:06:38,140
66, then the total number of possible combinations of finci four drops to one three to zero.

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00:06:38,650 --> 00:06:44,830
So now we would come to understand what is writing the encryption function, which we have written in

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00:06:44,830 --> 00:06:46,250
our fine cipher fight.

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00:06:46,720 --> 00:06:54,400
So let us close this key demo now as we have understood this and let's go back to this for now.

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00:06:54,400 --> 00:06:56,680
Here will come to the encrypt messages.

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00:06:57,520 --> 00:07:01,750
So now here, this is basically used to encrypt the given message.

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00:07:01,900 --> 00:07:02,990
Take the parameter.

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00:07:03,340 --> 00:07:10,930
Now we need to get the integer values for key A1 and we run from the get method that we have defined

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00:07:11,230 --> 00:07:14,110
by passing it on the particular key still.

81
00:07:14,380 --> 00:07:20,590
So next we check whether these guys are valid by passing them to the check estimator or what you know,

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00:07:20,860 --> 00:07:27,850
if your check function doesn't cause the program to exit, the keys are valid and the rest of the code

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00:07:27,850 --> 00:07:30,610
in the encrypt message function will execute.

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00:07:31,270 --> 00:07:32,260
So here we are.

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00:07:32,260 --> 00:07:38,830
Having the ciphertext is still a variable that starts as a blank string, but will eventually hold the

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00:07:38,830 --> 00:07:45,810
encrypted string, the for loop that begins iterate through each of the characters in your messages

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00:07:46,180 --> 00:07:51,300
and then add the encrypted character to your ciphertext Istria.