1.Introduction This standard specifies the Rijndael algorithm([3]and [4]),a symmetric block cipher that can process data blocks of 128 bits,using cipher keys with lengths of 128,192,and 256 bits. Rijndael was designed to handle additional block sizes and key lengths,however they are not adopted in this standard. Throughout the remainder of this standard,the algorithm specified herein will be referred to as "the AES algorithm."The algorithm may be used with the three different key lengths indicated above,.and therefore these different“flavors'”may be referred to as“AES-l28',“AES-l92”,and “AES-256” This specification includes the following sections: 2.Definitions of terms,acronyms,and algorithm parameters,symbols,and functions; 3.Notation and conventions used in the algorithm specification,including the ordering and numbering of bits,bytes,and words; 4.Mathematical properties that are useful in understanding the algorithm; 5.Algorithm specification,covering the key expansion,encryption,and decryption routines; 6.Implementation issues,such as key length support,keying restrictions,and additional block/key/round sizes. The standard concludes with several appendices that include step-by-step examples for Key Expansion and the Cipher,example vectors for the Cipher and Inverse Cipher,and a list of references. 2. Definitions 2.1 Glossary of Terms and Acronyms The following definitions are used throughout this standard: AES Advanced Encryption Standard Affine A transformation consisting of multiplication by a matrix followed by Transformation the addition of a vector. Array An enumerated collection of identical entities(e.g.,an array of bytes). Bit A binary digit having a value of 0 or 1. Block Sequence of binary bits that comprise the input,output,State,and Round Key.The length of a sequence is the number of bits it contains. Blocks are also interpreted as arrays of bytes. Byte A group of eight bits that is treated either as a single entity or as an array of 8 individual bits. 55 1. Introduction This standard specifies the Rijndael algorithm ([3] and [4]), a symmetric block cipher that can process data blocks of 128 bits, using cipher keys with lengths of 128, 192, and 256 bits. Rijndael was designed to handle additional block sizes and key lengths, however they are not adopted in this standard. Throughout the remainder of this standard, the algorithm specified herein will be referred to as “the AES algorithm.” The algorithm may be used with the three different key lengths indicated above, and therefore these different “flavors” may be referred to as “AES-128”, “AES-192”, and “AES-256”. This specification includes the following sections: 2. Definitions of terms, acronyms, and algorithm parameters, symbols, and functions; 3. Notation and conventions used in the algorithm specification, including the ordering and numbering of bits, bytes, and words; 4. Mathematical properties that are useful in understanding the algorithm; 5. Algorithm specification, covering the key expansion, encryption, and decryption routines; 6. Implementation issues, such as key length support, keying restrictions, and additional block/key/round sizes. The standard concludes with several appendices that include step-by-step examples for Key Expansion and the Cipher, example vectors for the Cipher and Inverse Cipher, and a list of references. 2. Definitions 2.1 Glossary of Terms and Acronyms The following definitions are used throughout this standard: AES Advanced Encryption Standard Affine A transformation consisting of multiplication by a matrix followed by Transformation the addition of a vector. Array An enumerated collection of identical entities (e.g., an array of bytes). Bit A binary digit having a value of 0 or 1. Block Sequence of binary bits that comprise the input, output, State, and Round Key. The length of a sequence is the number of bits it contains. Blocks are also interpreted as arrays of bytes. Byte A group of eight bits that is treated either as a single entity or as an array of 8 individual bits