Cipher Year Published Specification IETF Use IPR IPR Terms Type Parameters Key Length (bits) AES Compatible
KCipher-2 Stream Cipher 2011 draft-kiyomoto-kcipher2 2 Internet Drafts KDDI, Qualcomm RAND Stream 128-bit IV 128 No
ARIA 2010 RFC 5794 2 RFCs, 3 Internet Drafts None - Block 128-bit block 128, 192, 256 Yes
CLEFIA 2007 RFC 6114 1 RFCs, 3 Internet Drafts SONY RAND Block 128-bit block 128, 192, 256 Yes
SMS4 2006 200621016423197990.pdf None BDST Beijing Data Security Technology Co. Ltd. (BDST) Block 128-bit block 128 Partially
Rabbit 2006 RFC 4503 1 RFC Cryptico RAND Stream 64-bit IV 128 No
SEED 2005 RFC 4269 7 RFCs, 5 Internet Drafts None - Block 128-bit block 128 Partially
Camellia 2000 RFC 3713 15 RFCs, 22 Internet Drafts NTT Royalty free (needs IETF tools notification) Block 128-bit block 128, 192, 256 Yes
MISTY1 2000 RFC 2994 1 RFC Mitsubishi Royalty free (needs IETF tools notification) Block 64-bit block 128 No
CAST-256 1999 RFC 2612 13 RFCs Entrust Royalty free (needs IETF tools notification) Block 128-bit block 128, 160, 192, 224, 256 Yes
Advanced Encryption Standard (AES) 1998 FIPS-197 169 RFCs, 118 Internet Drafts None - Block 128-bit block 128, 192, 256 Yes
TWOFISH 1998 twofishAES.pdf 9 RFCs, 1 Internet Draft None - Block 128-bit block 128, 192, 256 Yes
Serpent 1998 serpent.pdf 6 RFCs, 2 Internet Drafts None - Block 128-bit block 128, 192, 256 Yes
SKIPJACK 1998 skipjack.pdf 15 RFCs, 3 Internet Drafts None - Block 64-bit block 80 No
RC2 1998 RFC 2268 36 RFCs, 10 Internet Drafts None - Block 64-bit block 8,16 24, ,...,1024 No
CAST-128 1997 RFC 2144 20 RFCs, 1 Internet Draft Entrust Royalty free (needs IETF tools notification) Block 64-bit block 128 No
RC4 Stream Cipher 1994 draft-kaukonen-cipher-arcfour 53 RFCs, 23 Internet Drafts None - Stream No IV 8,16, 24, ...,1024 No
RC5 1994 RFC 2420 25 RFCs, 6 Internet Drafts RSA needs IETF tools notification Block 32, 64, 128-bit block 8,16 24, ,...,1024 Yes
BLOWFISH 1994 paper-blowfish-fse.html 26 RFCs, 8 Internet Drafts None - Block 64-bit block 32, 64, 96, ...., 448 No
International Data Encryption Algorithm (IDEA) 1992 E90/389.PDF 9 RFCs, 2 Internet Drafts MediaCrypt AG Unknown; close to expiration Block 64-bit block 128 No
GOST 28147-89 1989 RFC 5830 8 RFCs, 7 Internet Drafts None - Block 64-bit block 256 No
Triple Data Encryption Standard (3DES) 1979 FIPS-46-3 143 RFCs, 56 Internet Drafts IBM Royalty free and expired Block 64-bit block 112 No
Data Encryption Standard (DES) 1977 FIPS-46 82 RFCs, 8 Internet Drafts IBM Royalty free and expired Block 64-bit block 56 No






























Notes








1. Highlighted ciphers are AES-compatible are free of intellectual property complications








2. AES-compatible ciphers have security goals and parameters that match those of the AES. Partially compatible ciphers support only some of the AES key lengths.








3. Not all ciphers have normative specifications.








4. Some IETF uses are self-citations.








5. Some RFCs have IPR considerations that are noted in the RFC text, but not in IETF tools.








6. The SMS4 cipher does not appear in any IETF documents, but it is included for comparison.




























Observations








1. No patented cipher has been added to an IETF standard since 1998, except those with royalty-free terms.








2. There are over 200 documents citing AES; if IETF includes new ciphers, it will be important to avoid a combinatorial explosion of new documents.








3. A framework for AES-compatible ciphers could be developed, to manage compatibility and to promote security.