What is "aes"

The AES (Advanced Encryption Standard ) or Advanced Encryption Standard, also known as Rijndael, is a block cipher adopted as the encryption standard by the United States government. It is expected to be used worldwide and analyzed extensively, as was its predecessor, the Data Encryption Standard (DES). AES has a fixed block size of 128 bits and a key size of 128, 192, or 256 bits, AES operates on a two-dimensional array of 4x4-position bytes, called a state (versions of Rijndael with a larger block size have additional columns in the state). To encrypt, each AES turn (except the last one) consists of four stages:

• Addroundkey - each state byte is combined with the turn’s own (Roundkey) subkey; each subkey is derived from the main key using the key-scaling algorithm.
• Subbytes - is a non-linear substitution step where each byte is replaced by another according to a reference table.
• Shiftrows - is a transposition stage where each row of the state is shifted from a certain number of positions.
• Mixcolumns - is a merge operation that operates on the state columns and combines the four bytes of each column using a linear transformation.