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Block Ciphers

Approved Algorithms

Currently, there exist three (3) Approved* encryption algorithms: AES, Triple DES, and Skipjack.

Advanced Encryption Standard (AES)

FIPS 197, Advanced Encryption Standard (AES), November 2001.

NIST is pleased to announce the approval of FIPS 197 Advance Encryption Standard which specifies the Rijndael encryption algorithm as a FIPS-approved symmetric encryption algorithm that may be used by U.S. Government organizations (and others) to protect sensitive information.

Federal agencies should also see OMB guidance.

Additional information regarding the use of AES can be found in CNSS Policy No. 15, Fact Sheet No. 1 National Policy on the Use of the Advanced Encryption Standard (AES) to Protect National Security Systems and National Security Information, June 2003.

Complete information on the AES development effort is available at the AES home page. Please note that these pages are included for historical reference only. As these pages refer to a development effort, they may contain errors. Refer to FIPS 197 for the actual specification of AES.

Triple DES

January 18, 2012: NIST announces the completion of revision 1 of Special Publication (SP) 800-67, Recommendation for the Triple Data Encryption Algorithm (TDEA) Block Cipher. This Recommendation specifies the Triple Data Encryption Algorithm (TDEA) block cipher, which includes a Data Encryption Algorithm (DEA) cryptographic engine that is implemented as a component of TDEA. DEA was originally specified in FIPS 46, The Data Encryption Standard, which became effective in 1977 and was reaffirmed in 1983, 1988, 1993, and 1999. FIPS 46 has now been withdrawn, but DEA is specified as a component function of TDEA.

FIPS 46-3, Data Encryption Standard (DES), October 1999, the former specification for Triple DES, has been withdrawn.


The declassified Skipjack algorithm was originally referenced in FIPS 185, Escrowed Encryption Standard (EES), February 1994.

NIST is providing a clarification regarding byte ordering to the specification for Skipjack.

FIPS 81, DES Modes of Operation, December 1980.

Skipjack may use any of the four (4) DES modes of operation (ECB, CBC, CFB, OFB) specified in FIPS 81. Also see the Block Cipher Modes Section.

Data Encryption Standard (DES)

FIPS 46-3, Data Encryption Standard (DES), October 1999.

On May 19, 2005 FIPS 46-3 was withdrawn is is no longer approved for Federal use.

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Testing Products

Testing requirements and validation lists are available from the Cryptographic Algorithm Validation Program (CAVP).

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Additional Information

July 10, 2015: NIST requests comments on a revision of Special Publication (SP) 800-131A, Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths, which was originally published in January 2011. The most significant differences in this revision are 1) declaring the Dual_EC_DRBG as a disallowed method for random bit generation, 2) the deprecation of the non-approved key-agreement and key-transport schemes, and the non-approved key-wrapping methods through December 31, 2017, and the intent to disallow them thereafter, and 3) the inclusion of the SHA-3 hash functions specified in FIPS 202.

Please submit comments by August 14, 2015 to, with "SP 800-131A Comments" in the subject line.

January 13, 2011: NIST announces the completion of Special Publication (SP) 800-131A, Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths. This Recommendation provides the approach for transitioning from the use of one algorithm or key length to another, as initially addressed in Part 1 of SP 800-57.

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Future Plans

Modes of Operation for the FIPS-approved encryption algorithms are available on the Modes of Operation page.

A draft of the AES Key Wrap specification is available on the Key Management page.

Note: An algorithm or technique that is either specified in a FIPS or NIST Recommendation.