Welcome to the next session in Biton advanced level course or python hacking advanced, of course,
in this session we have a look at programming Virginia for now, just an introduction.
Thought about Virginia's Saiful, the Italian cryptograph named Giovanni Batista was the first person
to describe the Virginia Saiful in the year fifteen fifty three.
But it was eventually named after a French diplomat, Blaise David Kinuyo, one of many people who invented
the SAIFUDDIN subsequently.
Now this Virginia Saiful remains unbroken until British polymath Charles Babbage broke it in the 19th
century, not because the original Saiful has too many plausible keys to the brute force.
Even with our English detection module, it's one of the strongest Saiful discussed so far.
So it's even invisible to the world.
But an attack that we have learned in the earlier sessions, not topics which going to cover in this
session are some keys and building strings using the list up and join forces now understanding force
using multiple kilojoule.
In the beginning, Saiful not unlike a Caesar salad for the original, Saiful has multiple keys because
it uses more than one set of substitutions.
Evgeniya Saiful is also known as all poly alphabetic substitution.
Saiful, unlike with the simple substitution, Saiful frequency analysis alone will not defeat the Virginia
Saiful.
Instead of using a new Morigi between zero to twenty five as we did in the Sisa Saiful, we use a little
key for the beginning of the beginning of is a CDs of letters such as an English word or single English
word that is split into multiple single letters.
Is that in plateau's in the plaintext.
Now let's just try to do this manually for.
So let's go to the back and see, for example, the beginning of saying this is the first stop is be
over here.
Second is I told and fourth letters of the plain text is the same that the Z and the fifth is a default
safety.
And the fourth letter of the plaintiff's second and second letter and so on.
When we get the sixth letter of the plaintext, we we're to the Fourth Circuit now using the beginning
of what is the same as using a multiple Caesar cipher instead of encrypting the whole plain text with
one Caesar Saiful.
We apply our differences aside for each letter of the plaintext.
For example, the four suppy would be the AP 15 second would be c e i h told would be C is head twenty
five.
Then it may be is it twenty five against the would be eight zero.
Now each piece converted into an integer also and so does a Caesar Saiful use for example a corresponds
to see the Saiful key here that is zero and the B corresponds to the key one and so on opposite.
So here we would replace C, A and Z to say twenty five in this case.
So now let's look at an example.
Now we'll have the following message like C let's go on a new line.
Say Common sense is not so common and over here we will have the beginning of giving us a piece isn't.
Now, for every character over here, this will not find it.
What we would do is let's go to X and Hillary would see.
Common sense is not so common now let's just place it properly so that we can place the beginning work
below that, so we can combine that together because you just required characters to be displayed so
the colvert could be or easily adjusted to the character of it.
Now.
Let's just place it over here and he'll be all right down to A, B, C, d, e, f, g, h, i, j,
k, l, m and I will be cool as
v, w, x, y, z.
And over here we would just give the.
He's for this starting from zero one, two, three, four, five, six, seven, eight, nine, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20.
Twenty four point five, and then we have taken this, let's write down
every bit, we will repeat this key multiple times
like this.
So now if we are supposed to encrypt CESI in the plain text, would the subject be if we encrypt Ozzies,
a cipher using a suppy corresponding numeric 15, which will result in a little.
Ah, because if you see this too, if you see B, it is 15, 15 plus two comes to 17.
That is OK.
And this will repeat the process for each letter of the plaintext by cycling through this piece.
So let us try and get to the output that we would get when we encrypt.
So if we take this, you will get it for see the characters they are, then you will get it for all
C, W, then L, L, because and Z that is common.
Hence we will get the same character that also say or c e d m.
S d q.
Are M or I?
A and B, who be you, and then if so, this would be actually your decrypted text so long ago, the
Virginia Keys are there, they are more secure in the reason that the more wrong it is, the more combinations
you would have.
So the more likely in the beginning, the stronger the encrypted message will be against the brute force
attack.
So over here, the key that we have taken was a very poor choice because it has only five letters A
or I'll give it the five letters will have only limited combinations because twenty six letters to the
power of five point sixty five will be somewhere around one one eight eight one three seven six one.
So 11 million keys are far too many for human to brute force, but a computer can try them all just
in some few hours.
So it would be or it would force try to decrypt the particular message using the key all five times
E and check whether the resulting decryption was in English.
It would then try to say by A, B or C until it goes to the key piece.
And the good news is that for every additional letter, the key has the number of possible places that
many twenty six times.
So once there are of quadrants of possible what take a computer many years to break.