Now, let's have a look at some examples of symmetric encryption in the last lecture, we did talk about
asymmetric encryption and asymmetric encryption has one key, which we used to encrypt the message as
well as decrypt the message.
And that key is known as the security.
So the first example of symmetric encryption is to fish algorithm, not to fish algorithm has 128 bits
of blogsite.
Now, what do I mean by block?
Size is at a time 128 bits of data will get encrypted by using a key off 256 bits.
All right.
Now, you must have a question how 128 and 256 keys work together.
It's twice the value.
So the algorithm has such steps, which reduces the key size, then manipulates the input and then finally
encrypted document.
If we dive deep into the algorithms of each and every example, you will get confused.
So what we are trying to tell you here is at a time 128 bits of data will get encrypted in one block
and using a key of two hundred and fifty six bits.
Similarly, the next standard is data encryption standard, which was developed by the National Institute
of Standards and Technology.
This is very old standard and it is very basic standard.
When the researchers had invented because they thought that it is not unbreakable.
It is.
It is unbreakable.
But some researchers prove that it is breakable and that is why they developed the advance standard.
So for data encryption standard at a time only 64 bits of data can be encrypted and the key size is
fifty six bits.
So as I said, as soon as researchers, you know, they proved that this is not secure and can be attacked,
they developed the advanced encryption standard.
I'm sorry, here.
It must be 86 now.
Eight years has three different versions in place.
So iOS has three different origins.
So the first version has 128 bits of block size and 128 bits of key size.
The second version has 128 bits of block size and 192 bits of key size, and a third version has 128
bits of block size and 256 bits of key size.
So more the key size here, more the key size.
Higher is the security.
But again, time consumption will also increase.
So it depends upon different organizations and programs which encryption they should use.
But nowadays, almost every encryption standard uses the advanced encryption scheme, which is very
helpful.
The next example of symmetric encryption is reversed.
Saiful are C4, which which was very which was invented long ago by one of the scientists and he contributed
to an asymmetric encryption as well.
So Odyssey four has a variable and it's a stream cipher.
We have seen the difference between a stream cipher and a block, so variable length of stream cipher
in which the data input is in the form of stream.
It's a continuous stream of data input and the key size can be 64 bits or 128 bits.
Similarly, Odyssey five Volgin was there are different types of block.
Now RC five starts with a block, but Odyssey four is streamside four.
And the key again is variable.
It can be zero to 255 bits.
And finally, Odyssey's six has 16, 32, 64 bits of block size and zero to two.
Now, what's the difference between these two here?
What is the difference there?
Here, only two bit registers were used while performing the operations.
But here, Forbert registers are used for its advanced version of Odyssey five.
Here in BIJA, multiplication was not done, whereas here integer multiplication is performed.
So you can see that Odyssey six is much advanced version of Odyssey five, not algorithms of all these
encryptions are very difficult to understand.
That is why we haven't included the lectures.
So I tell you how exactly these encryption algorithms work.
If we do so, if we plan to do a course on cryptography, will surely include everything in detail.
But for timing, we are not going to dive deep into how exactly these numbers play.
So if you if you have any exams or interviews, you have to make sure that you have to remember these
numbers right here.
So now how what is the main drawback of symmetric encryption?
Well, according to the definition, symmetric encryption has only one key.
And suppose we have Bob here and we have Alice.
So how exactly are you going to share the key to Bob?
And I mean, how exactly are you going to share the same key?
Because even if the attacker gets to know the key, he gets to know everything.
So secure sharing of keys is the drawback of asymmetric encryption.
So how exactly will Bob share the key which he used to decode, encrypt the message so that Alice can
decrypt?
Now, some of you may say that we can again encrypt the key, but again, for that encryption, you
will also have one key.
So this process is very tedious and that is why there is one algorithm, Diffie Helmond Key Exchange
algorithm, which was founded out by two people, outstanding brains that overlap the algorithm, which
we will be seeing in later part of this code.
So that that algorithm actually gives us a V in order to share a security.
I will be showing you true graphics, how you actually can achieve that.
All right.
In the next lecture, we will be talking about asymmetric encryption where we will be having a look
versus asymmetric and asymmetric encryption.
All right.
Stay tuned.
Keep moving forward.
I will see you in the next lecture.