AES Encryption Algorithm

AES is a newer encryption standard and is now the preferred one to use for XML Encryption. AES is a substitution-linear transformation network with 10, 12, or 14 rounds, depending on the key sizes, which are currently set at 128, 192, or 256 bits. The block size used in AES is 16 bytes.

The data block to be processed is partitioned into an array of bytes forming a matrix with rows and columns . Each cipher operation is byte-oriented.

The next step has four layers :

1. An 8-by-8 substitution box is applied to each byte.
   
   
2. Two layers of linear mixing are performed in which the rows of the byte array are shifted and the columns are mixed.
   
   
3. Subkey bytes are combined into each byte of the array using XOR.
   
   
4. The column mixing is omitted in the last round.
   
   

The algorithm was designed to be very fast and suitable to hardware.