Encrypts and decrypts using the AES Rijndael Block Cipher Algorithm.This might be the case when the key does not need to be changed (and so it can be stored in its expanded form) or when the key does not change very often (and thus it can be expanded more slowly in software). In some cases a key expander is not required. This is because the core uses the expanded key backwards during decryption. For decryption, though, the key must be pre-expanded and stored in an appropriate memory before being used by the AES core. The CAST KEXP AES key expander core is available as an AES core option.ĭuring encryption, the key expander can produce the expanded key on the fly while the AES core is consuming it. The AES algorithm requires an expanded key for encryption or decryption. The cipher is output after the final round. The final round is anomalous as the MixColumn step is skipped. These operations are repeated according to the number of rounds. At the end of each round, the new state is stored in the State Storage area. The state information is then retrieved and the ByteSub, Shiftrow, MixColumn, and AddRoundKey functions are performed on it in the specified order. The result is stored in the State Storage area. Initially, the incoming data and the key are added together in the AddRoundKey module. Number of rounds as a function of key size. The intermediate cipher result is known as state. The number of rounds depends on the size of the key and the data block. The AES algorithm consists of a series of steps repeated a number of times (rounds). The key is expanded during cryptographic operations. The encryption key can be chosen among three different sizes: 128-, 192- or 256-bit. An AES encryption operation transforms a 128-bit block into a block of the same size.

Aes 128 bits