Data encryption Standard

It uses feistel structureand has total of 16 rounds has has separate independent 16*2 key from master key by left .
It is block cipher algorithmn.
Support only 64 bit and divide into 2 parts of 32 bit each. Size of key is 64 where 8 bits are escalaeted for comparing/checking parity.

Size of sub key is 28 bit each . Size of cipher text is 64 bit.
There are three basic process in DES . They are described below:
1)Expansion : 32 bits are converted to 48 bit using expansion permutation by duplicating bits.
2)Key miing: Result after expansion is xor'ed with key .
3)Substitution :S-box or substitution box is used which is core of DES for security.

Advanced encryption standard

It is also block cipher algorithmn where whole block is processed at once where block size and key size are not specified and can be either 128 bit, 192 bit, 256 bit etc. Similar to DES , the blocks are processed in ten rounds with separate sub keys generated form master key . Master key are processed in terms of word which is of 32 bit, so there are four word or 16 bytes.

No of subkeys : 44 subkeys
Size of subkey: 32 bit / 1 word/4 bytes
For each round we are going to use 4 subkeys(128 bit or 4 word or 16 bytes)
So total 40 subkeys are used in 10 rounds.
In pre-round calculation 4 subkeys/4 word / 16 bytes are used .

Bock diagramme of AES algorithmn