So let's talk about this decision to save lives.
We have already seen the substitution for substitute the brain by some other characters, so the characters
are brain substituted by other characters.
And the weakness of these operations over there can easily be brute force.
So you can try all the combination of substitute characters and you can get a meaningful plaintext in
one attempt and then the advantages can easily be encrypted.
So let's see some examples of these obstetrician's efforts to get more idea about this.
So first one, we're going to see the scissors four, and this is the very basics if you people that
come to know when you're.
So what deciphered the stories you need to write down all the alphabets.
And these alphabet contains something indexes.
So Index B's, one index and so on up to the this index.
So we have indexes of integer are from zero point zero one, two, three, four, five, six and so
on.
So if you have a plain text and you pick, you have to apply character-based.
So you take the first character and find that index.
So after finding that index, you need to determine some key.
So this is where you need to determine some key and you need to add that index to it.
So index Peski, you get some value and what you want you want to do better is because if the value
of index is like 20 and if there is value of the gift, then it will go out of this table.
Right.
Because the limit is twenty and we get 30 on addition.
That's what we need to moderate the word politics so that we only consider the remainder of this division.
So first we take the index of, uh, the character in the plain text and we manually determine some
key.
And then we add that index and key and then we the world with 36, such that the cipher text will be
only in this range.
So let's take a look at this example.
So this is the table zero contents here and one B to C and so on.
So I'm going to take an example.
The plain text is empty, Wajir, so think it as an abbreviation.
I know I have already determined the key is equal to six.
So we need to do the Caesar's apparatuses for each and every character.
Let's take you.
So in the previous table, let's find out the index of it.
So is it the index?
And you need to press the key, which is six six zero six six and after only 26, 26 goes in zeros and
then 206.
And why do we take a look at the six in the table?
You get the value.
So write it down.
So over here in the plaintext has been converted into G in the same for the same that you take them
to at least four and then you add six, which you 18 and then 26 since the trust, then 26 goes 18 and
zero times and leaves the room under 18.
So the answer is 18.
And if you take a look at the table, 13 values is so you write it down.
So instead of your keeping us in the same way, you can do the every letter.
Let's take a look at this.
Right.
The index of what you can differ.
And if we are six, you get thirty.
So our boundary has been zero.
So the answer got all the different.
So that's what we will do.
The Modular 26, because we get only reminders from Dero to quantify.
If you do a right, that's what we will do.
The Model 26.
So that might be good for.
So 26 once is equal 26 and plus four gives thirty.
Right.
And for is eat the same that the 12.
And then if you are six you get 31.
And if you want to do it but only six you get the value of a year.
So in that way we get the ciphertext final.
Yes, yes.
Yes.
So you should have.
We already have here we are adding us to Egypt, Loihi and the transfer of Savannakhet ciphertext will
be.
Yes.
That if we send the key also to our receiver and then he just adds minus in the same way to get this
plaintext, he put the minus and to the wider region and he get the value of the plaintext.
So this is one of the example orders of protection.
The weakness lies because the keys machsom keys, if you can produce, even though if you put the infinity,
this modular condition, six use only that can be possible.
So you can just apply the key to this plaintext and you can generate 25 different sets of ciphertext
in those different sets.
One set will be the meaningful because our plaintext will be meaningful.
I took just this an example to show you the starting letters and letters and letters.
So in reality, the plain text will be meaningful, that that's why Hacker will use this.
If he knows the key and if he knows that we have used the same text, he simply put forces and he gets
for in 24 hours.
It's easy to find a meaningful sentence.
Right?
That's why it is easy repropose.
And next example, we are going to seize the nerve center and what we're going to do is we're going
to create a table and the rules and columns are created by Alphabet's.
You need to create a table with the date and the rules and columns should also be the same and key should
be exactly the same plain text.
So it contains 10 characters.
The key should be also 10 characters.
If not, repeat the key.
That means if the character in this print distance and the keys for we need to repeat it again.
Four and you get the key is it so you get the remaining rate.
That means you need to fill up two margaritas and you can distribute the two more characters are the
key.
So that's how you make sure that the exact, uh, the print accident and the current are equal and no
mapping should be done between the plain text alphabets column and the keys are true.
So you take each alphabet of plaintext and you cancel the column of the drawer of the table and the
key are Pavitra and offer the mapping.
You will get the one value and that value is the same for text.
So let me explain.
So this is the table.
I have taken this photo from the Internet because I cannot I cannot create this in this much trouble.
So you have those ABCDE, you do it again and your columns here to get.
Now let's take an example.
So print technical.
Okay, this is my name.
And the keys I take since the incident is less than plaintext, we need to repeat the key.
So what we're going to do is we need to change it.
So in this case, we got the.
Exactly the multiverse.
If you have only killed two, you need to Nicole here.
You need to put it here.
You just simply repeat until the plaintext characters are equal to key characters.
So first, I want to take this first half of it and second half of it, which look at the end column.
So in this end column, I need to look at the hits or so and column and hetero.
So and Khorram, sorry, so much so, so I take this and call them.
And so it is you.
So my brain trying to transform into you in the same way I cut my throat.
So we decided to call them and they throw it.
And in the same way.
So here is it's a kid column and drop and kid column, which are.
So it's all you can find all this and let's see the last one I Iroh.
Your column, Iroh.
And so the ciphertext of the plane technically is UCU are PBT, so these two survivors are example of
substitution ciphers.
There are so many substitutions out there, but I cannot tell everything.
There are not more than experts.
So I took this to mean SEYFERT because I want to show you a whole substitution.
Ciphers will work and no one can prove Forcett and you can also check it.
Other substitutions I put on the Internet as well.
But my intention is to show you that how this operation works.
That's all for this video.