Processing Standards Publication 197
November 26, 2001
ADVANCED ENCRYPTION STANDARD (AES)
Federal Information Processing Standards Publications (FIPS PUBS) are issued by the National
Institute of Standards and Technology (NIST) after approval by the Secretary of Commerce
pursuant to Section 5131 of the Information Technology Management Reform Act of 1996
(Public Law 104-106) and the Computer Security Act of 1987 (Public Law 100-235).
Name of Standard. Advanced Encryption Standard (AES) (FIPS PUB 197).
Category of Standard. Computer Security Standard, Cryptography.
Explanation. The Advanced Encryption Standard (AES) specifies a FIPS-approved
cryptographic algorithm that can be used to protect electronic data. The AES algorithm is a
symmetric block cipher that can encrypt (encipher) and decrypt (decipher) information.
Encryption converts data to an unintelligible form called ciphertext; decrypting the ciphertext
converts the data back into its original form, called plaintext.
The AES algorithm is capable of using cryptographic keys of 128, 192, and 256 bits to encrypt
and decrypt data in blocks of 128 bits.
Approving Authority. Secretary of Commerce.
Maintenance Agency. Department of Commerce, National Institute of Standards and
Technology, Information Technology Laboratory (ITL).
Applicability. This standard may be used by Federal departments and agencies when an
agency determines that sensitive (unclassified) information (as defined in P. L. 100-235) requires
Other FIPS-approved cryptographic algorithms may be used in addition to, or in lieu of, this
standard. Federal agencies or departments that use cryptographic devices for protecting classified
information can use those devices for protecting sensitive (unclassified) information in lieu of
In addition, this standard may be adopted and used by non-Federal Government organizations.
Such use is encouraged when it provi