Cipher security summary


This article summarizes publicly known attacks against block ciphers and stream ciphers. Note that there are perhaps attacks that are not publicly known, and not all entries may be up to date.

Table color key

Best attack

This column lists the complexity of the attack:
  • If the attack doesn't break the full cipher, "rounds" refers to how many rounds were broken
  • "time" — time complexity, number of cipher evaluations for the attacker
  • "data" — required known plaintext-ciphertext pairs
  • "memory" — how many blocks worth of data needs to be stored
  • "related keys" — for related-key attacks, how many related key queries are needed

    Common ciphers

Key or plaintext recovery attacks

Attacks that lead to disclosure of the key or plaintext.
CipherSecurity claimBest attackPublish dateComment
AES12821282011-08-17Independent biclique attack.
AES19221922011-08-17Independent biclique attack.
AES25622562011-08-17Independent biclique attack.
BlowfishUp to 24484 of 16 rounds; 64-bit block is vulnerable to SWEET32 attack.2016Differential cryptanalysis. Author of Blowfish recommends using Twofish instead. SWEET32 attack demonstrated birthday attacks to recover plaintext with its 64-bit block size, vulnerable to protocols such as TLS, SSH, IPsec, and OpenVPN, without attacking the cipher itself.
Twofish2128 – 22566 of 16 rounds 1999-10-05Impossible differential attack.
Serpent-128212810 of 32 rounds 2002-02-04Linear cryptanalysis.
Serpent-192219211 of 32 rounds 2002-02-04Linear cryptanalysis.
Serpent-256225611 of 32 rounds 2002-02-04Linear cryptanalysis.
DES256239 – 243 time, 243 known plaintexts2001Linear cryptanalysis. In addition, broken by brute force in 256 time, no later than 1998-07-17, see EFF DES cracker. Cracking hardware is available for purchase since 2006.
21682113 time, 232 data, 288 memory; 64-bit block is vulnerable to SWEET32 attack.2016Extension of the meet-in-the-middle attack. Time complexity is 2113 steps, but along with proposed techniques, it is estimated to be equivalent to 290 single DES encryption steps. The paper also proposes other time–memory tradeoffs. SWEET32 attack demonstrated birthday attacks to recover plaintext with its 64-bit block size, vulnerable to protocols such as TLS, SSH, IPsec, and OpenVPN.
KASUMI2128232 time, 226 data, 230 memory, 4 related keys2010-01-10The cipher used in 3G cell phone networks. This attack takes less than two hours on a single PC, but isn't applicable to 3G due to known plaintext and related key requirements.
RC4Up to 22048 2007Commonly known as PTW attack, it can break WEP encryption in Wi-Fi on an ordinary computer in negligible time. This is an improvement of the original Fluhrer, Mantin and Shamir attack published in 2001.

Distinguishing attacks

Attacks that allow distinguishing ciphertext from random data.
CipherSecurity claimBest attackPublish dateComment
RC4up to 22048 2000Paper.

Less-common ciphers

Key recovery attacks

Attacks that lead to disclosure of the key.
CipherSecurity claimBest attackPublish dateComment
CAST 264248 time, 217 chosen plaintexts1997-11-11Related-key attack.
CAST-12821286 of 16 rounds 2009-08-23Known-plaintext linear cryptanalysis.
CAST-256225624 of 48 rounds 2009-08-23Known-plaintext linear cryptanalysis.
IDEA21282012-04-15Narrow-biclique attack.
MISTY121282015-07-30Chosen-ciphertext, integral cryptanalysis, an improvement over a previous chosen-plaintext attack.
RC2264 – 2128Unknown time, 234 chosen plaintexts1997-11-11Related-key attack.
RC52128
SEED2128
Skipjack280280ECRYPT II recommendations note that, as of 2012, 80 bit ciphers provide only "Very short-term protection against agencies". NIST recommends not to use Skipjack after 2010.
TEA21281997-11-11Related-key attack.
XTEA2128
XXTEA2128259 chosen plaintexts2010-05-04Chosen-plaintext, differential cryptanalysis.

Distinguishing attacks

Attacks that allow distinguishing ciphertext from random data.
CipherSecurity claimBest attackPublish dateComment
CAST-25622562012-12-04Multidimensional zero-correlation cryptanalysis.