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
[edit] No known successful attacks — attack only breaks a reduced version of the cipher
Theoretical break — attack breaks all rounds and has lower complexity than security claim
Attack demonstrated in practice
Best attack
[edit]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 (if applicable)
- "memory" — how many blocks worth of data needs to be stored (if applicable)
- "related keys" — for related-key attacks, how many related key queries are needed
Common ciphers
[edit]Key or plaintext recovery attacks
[edit]Attacks that lead to disclosure of the key or plaintext.
| Cipher | Security claim | Best attack | Publish date | Comment |
|---|---|---|---|---|
| AES128 | 2128 | 2126.1 time, 288 data, 28 memory | 2011-08-17 | Independent biclique attack.[1] |
| AES192 | 2192 | 2189.7 time, 280 data, 28 memory | ||
| AES256 | 2256 | 2254.4 time, 240 data, 28 memory | ||
| Blowfish | Up to 2448 | 4 of 16 rounds; 64-bit block is vulnerable to SWEET32 attack. | 2016 | Differential cryptanalysis.[2] Author of Blowfish (Bruce Schneier) recommends using Twofish instead.[3] 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.[4] |
| Twofish | 2128 – 2256 | 6 of 16 rounds (2256 time) | 1999-10-05 | Impossible differential attack.[5] |
| Serpent-128 | 2128 | 10 of 32 rounds (289 time, 2118 data) | 2002-02-04 | Linear cryptanalysis.[6] |
| Serpent-192 | 2192 | 11 of 32 rounds (2187 time, 2118 data) | ||
| Serpent-256 | 2256 | |||
| DES | 256 | 239 – 243 time, 243 known plaintexts | 2001 | Linear cryptanalysis.[7] In addition, broken by brute force in 256 time, no later than 1998-07-17, see EFF DES cracker.[8] Cracking hardware is available for purchase since 2006.[9] |
| Triple DES | 2168 | 2113 time, 232 data, 288 memory; 64-bit block is vulnerable to SWEET32 attack. | 2016 | Extension 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.[10] SWEET32 attack demonstrated birthday attacks to recover plaintext with its 64-bit block size, vulnerable to protocols such as TLS, SSH, IPsec, and OpenVPN.[4] |
| KASUMI | 2128 | 232 time, 226 data, 230 memory, 4 related keys | 2010-01-10 | The 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.[11] |
| RC4 | Up to 22048 | 220 time, 216.4 related keys (95% success probability) | 2007 | Commonly known as PTW attack, it can break WEP encryption in Wi-Fi on an ordinary computer in negligible time.[12] This is an improvement of the original Fluhrer, Mantin and Shamir attack published in 2001.[13] |
Distinguishing attacks
[edit]Attacks that allow distinguishing ciphertext from random data.
| Cipher | Security claim | Best attack | Publish date | Comment |
|---|---|---|---|---|
| RC4 | up to 22048 | ?? time, 230.6 bytes data (90% probability) | 2000 | Paper.[14] |
Less-common ciphers
[edit]Key recovery attacks
[edit]Attacks that lead to disclosure of the key.
| Cipher | Security claim | Best attack | Publish date | Comment |
|---|---|---|---|---|
| CAST (not CAST-128) | 264 | 248 time, 217 chosen plaintexts | 1997-11-11 | Related-key attack.[15] |
| CAST-128 | 2128 | 6 of 16 rounds (288.51 time, 253.96 data) | 2009-08-23 | Known-plaintext linear cryptanalysis.[16] |
| CAST-256 | 2256 | 24 of 48 rounds (2156.2 time, 2124.1 data) | ||
| IDEA | 2128 | 2126.1 time | 2012-04-15 | Narrow-biclique attack.[17] |
| MISTY1 | 2128 | 269.5 time, 264 chosen plaintexts | 2015-07-30 | Chosen-ciphertext, integral cryptanalysis,[18] an improvement over a previous chosen-plaintext attack.[19] |
| RC2 | 264 – 2128 | Unknown[clarification needed] time, 234 chosen plaintexts | 1997-11-11 | Related-key attack.[15] |
| RC5 | 2128 | Unknown | ||
| SEED | 2128 | Unknown | ||
| Skipjack | 280 | 280 | ECRYPT II recommendations note that, as of 2012, 80 bit ciphers provide only "Very short-term protection against agencies".[20] NIST recommends not to use Skipjack after 2010.[21] | |
| TEA | 2128 | 232 time, 223 chosen plaintexts | 1997-11-11 | Related-key attack.[15] |
| XTEA | 2128 | Unknown | ||
| XXTEA | 2128 | 259 chosen plaintexts | 2010-05-04 | Chosen-plaintext, differential cryptanalysis.[22] |
Distinguishing attacks
[edit]Attacks that allow distinguishing ciphertext from random data.
| Cipher | Security claim | Best attack | Publish date | Comment |
|---|---|---|---|---|
| CAST-256 | 2256 | 28 of 48 rounds (2246.9 time, 268 memory, 298.8 data) | 2012-12-04 | Multidimensional zero-correlation cryptanalysis.[23] |
See also
[edit]- Block cipher
- Hash function security summary
- Time/memory/data tradeoff attack
- Transport Layer Security
- Bullrun (decryption program) — a secret anti-encryption program run by the U.S. National Security Agency
References
[edit]- ^ Vincent Rijmen (1997). "Cryptanalysis and Design of Iterated Block Ciphers". Ph.D. Thesis.
- ^ Dahna McConnachie (2007-12-27). "Bruce Almighty: Schneier preaches security to Linux faithful". Computerworld. Archived from the original on 2012-06-03. Retrieved 2014-02-13.
- ^ a b Karthikeyan Bhargavan, Gaëtan Leurent (August 2016). "On the Practical (In-)Security of 64-bit Block Ciphers — Collision Attacks on HTTP over TLS and OpenVPN". ACM CCS 2016.
- ^ Niels Ferguson (1999-10-05). "Impossible Differentials in Twofish". Schneier.
- ^ Eli Biham; Orr Dunkelman; Nathan Keller (2002-02-04). Linear Cryptanalysis of Reduced Round Serpent. FSE 2002. doi:10.1007/3-540-45473-X_2.
- ^ Junod, Pascal (2001). On the Complexity of Matsui's Attack. Selected Areas in Cryptography. pp. 199–211. Archived from the original on 2009-05-27.
- ^ "DES Cracker Project". EFF. Archived from the original on May 7, 2017. Retrieved August 26, 2015.
On Wednesday, July 17, 1998 the EFF DES Cracker, which was built for less than $250,000, easily won RSA Laboratory's "DES Challenge II" contest and a $10,000 cash prize.
- ^ "COPACOBANA – Special-Purpose Hardware for Code-Breaking".
- ^ Stefan Lucks (1998-03-23). "Attacking Triple Encryption". Fast Software Encryption. Lecture Notes in Computer Science. Vol. 1372. Springer. pp. 239–253. doi:10.1007/3-540-69710-1_16. ISBN 978-3-540-64265-7.
- ^ Orr Dunkelman; Nathan Keller; Adi Shamir (2010-01-10). "A Practical-Time Attack on the A5/3 Cryptosystem Used in Third Generation GSM Telephony". Cryptology ePrint Archive.
- ^ Erik Tews; Ralf-Philipp Weinmann; Andrei Pyshkin (2007). Breaking 104 Bit WEP in Less Than 60 Seconds. WISA 2007.
- ^ Scott Fluhrer; Itsik Mantin; Adi Shamir (2001-12-20). Weaknesses in the Key Scheduling Algorithm of RC4 (PDF). Selected Areas in Cryptography 2001.
- ^ Scott R. Fluhrer; David A. McGrew. Statistical Analysis of the Alleged RC4 Keystream Generator (PDF). FSE 2000. pp. 19–30. Archived from the original (PDF) on 2014-05-02.
- ^ a b c John Kelsey; Bruce Schneier; David Wagner (1997-11-11). "Related-key cryptanalysis of 3-WAY, Biham-DES, CAST, DES-X NewDES, RC2, and TEA". In Yongfei Han; Tatsuaki Okamoto; Sihan Quing (eds.). Information and Communications Security: First International Conference. Vol. 1334. Springer. pp. 233–246. CiteSeerX 10.1.1.35.8112. doi:10.1007/BFb0028479. ISBN 978-3-540-63696-0.
- ^ Meiqin Wang; Xiaoyun Wang; Changhui Hu (2009-08-23). "New Linear Cryptanalytic Results of Reduced-Round of CAST-128 and CAST-256". Selected Areas in Cryptography. Lecture Notes in Computer Science. Vol. 5381. pp. 429–441. doi:10.1007/978-3-642-04159-4_28. ISBN 978-3-642-04158-7. S2CID 35612393.
- ^ Achiya Bar-On (2015-07-30). "A 270 Attack on the Full MISTY1". Cryptology ePrint Archive.
- ^ Yosuke Todo (2015-07-06). Integral Cryptanalysis on Full MISTY1. CRYPTO 2015.
- ^ "ECRYPT II Yearly Report on Algorithms and Keysizes (2011-2012)" (PDF). CORDIS. 30 September 2012. D.SPA.20 Rev. 1.0, ICT-2007-216676 ECRYPT II.
- ^ Transitions: Recommendation for Transitioning the Use of Cryptographic Algorithms and Key Lengths, NIST
- ^ Elias Yarrkov (2010-05-04). "Cryptanalysis of XXTEA". Cryptology ePrint Archive.
- ^ Andrey Bogdanov; Gregor Leander; Kaisa Nyberg; Meiqin Wang (2012-12-04). "Integral and multidimensional linear distinguishers with correlation zero" (PDF). Advances in Cryptology – ASIACRYPT 2012: 18th International Conference on the Theory and Application of Cryptology and Information Security. Vol. 7658. Springer. pp. 244–261. doi:10.1007/978-3-642-34961-4. ISBN 978-3-642-34960-7. S2CID 26601027.
