Cryptography Algorithm

1)AES is ADVANCE ENCRYPTION STANDARD its is a symmetric key

block cipher .

2)AES has number of rounds each round makes a number of

transformations on a state and uses a round key derived

from encryption key.

3) number of block depends upon block size

4)an encryption of a block starts with a transformation

AddRoundkey this is followed by and odd number of regular

rounds and ends with a special final round.

5)the final round helps in decryption.

6) basic principle used is substitution permutation network.

7)aes has block size of 128 bits and key size of 128 192 or

256 bits

8)rounds are :

1)addroundkey-each byte of the state is combined with round

key using bitwise X-OR.

2)subbytes- each byte is replaced by another byte according

to lookup table

3)shiftRow-a transposition step where each row of the state

is shifted cyclically a certain number of steps

4)mix column-combination of 4 bytes takes palce in each column

5)final round