Rijndael is an iterated block cipher that supports key and block lengths of 128 to 256 bits in steps of 32 bits. It transforms a plaintext block into a ciphertext block by iteratively applying a single round function alternated by the addition (XOR) of a round keys. The round keys are derived from the cipher key by means of a key schedule. As a result of the wide trail strategy, the round function of Rijndael consists of three dedicated steps that each have a particular role. Rijndael versions with a block length of 128 bits, and key lengths of 128, 192 and 256 bits have been adopted as the Advanced Encryption Standard (AES).