And finally we'll take a look at an algorithm that does guarantee maximum security the Advanced Encryption
Standard for it was entered into the competition with management it was bought by two Belgian cryptographers.
The Advanced Encryption Standard is also offered to retail from the name of its creator.
The difference between the two is that Greendale is more flexible some rain they'll support a block
size and key size combinations.
But if you get past the algorithm doesn't support these options.
Now the winning cipher was selected in 2000 over 12 years ago.
Ringtail over the Scifres Mars RC 6 serpent and Twofish
RC 6 which we know about already was developed by Ron Rivest while Twofish like its predecessor Blowfish
was created by Bruce Schneier.
Another big name in cryptography.
Now some details on it.
Yes
the cipher uses a killing of 128 to 256 bits it encrypts data blocks of fixed 128 bit length the number
of rounds depends on the size of the key
suggested key today should be 256 bits in length.
Although the markets are.
There will be 14 rounds in this configuration.
It's interesting to note that the Advanced Encryption Standard does not use Feistel network
the structure that it uses is hard to talk about without an animation or a graphical aid.
For now remember that the round number is determined by the length of the key each round uses around
key for each round for what.
For They're divided into layers.
The first is the nonlinear layer.
The next is the mixing layer and the third is the key addition layer the non-linear layer it's a crucial
stage.
As you already know from the D.S. analysis substitutions are made in this layer to hide relationships
between the plaintext and the ciphertext.
So let's now take a closer look into yes.
Before this a couple of words on terminology we'll use the term state a state is intermediate form in
plaintext encryption or in other words it's the changing plain text values at each stage of the ABs
encrypting process.
States will be displayed as tables bytes of input messages will be in the intersection of columns and
rows in the table.
Likewise you can imagine the key to be displayed as a table.
The first transformation the nonlinear transformation is the most important one.
It's called the subsites the
substitution boxes again used.
And again we'll locate a value of the ciphertext bits based on the values of the plaintext bits.
This relationship is completely non-linear.
The second step involves shifting rows and moving columns.
This is a simple operation that relies on shifting each row to the left mixing each column.
The goal again is to obscure any relationships between the key and the ciphertext.
In each round except the final round rows and column positions are transposed the final round involves
only row shifting at the end of each round.
The key is combined with the state the ADD round key operation is used for this purpose.
The steps in total result in an efficient and very secure algorithm.
The main appeal is the fact that it's a standard.
If you're unsure which cipher to use for your solution I recommend the Advanced Encryption Standard.
No one ever got fired for implementing an adopted standard even if a yes within five or 10 years proved
to have some now unknown deficiencies which is unlikely because of one of the biggest strengths of public
algorithms is that they're subjected to very intensive testing.
You can always defend yourself saying that you have implemented the standard you can't be blamed for
failing to predict it and have some faults.