Cryptomeria cipher
Feistel network | |
| Rounds | 10 |
|---|---|
| Best public cryptanalysis | |
| A boomerang attack breaks all 10 rounds in 248 time with known S-box, or 253.5 with an unknown S-box, using 244 adaptively chosen plaintexts/ciphertexts. [1] | |
The Cryptomeria cipher, also called C2, is a
Cipher details
The C2
The 4C Entity licenses a different set of S-boxes for each application (such as DVD-Audio, DVD-Video and CPRM).[2]
Cryptanalysis
In 2008, an attack was published against a reduced 8-round version of Cryptomeria to discover the S-box in a chosen-key scenario. In a practical experiment, the attack succeeded in recovering parts of the S-box in 15 hours of CPU time, using 2 plaintext-ciphertext pairs.[2]
A paper by Julia Borghoff,
Distributed brute force cracking effort
Following an announcement by Japanese HDTV broadcasters that they would start broadcasting programs with the copy-once broadcast flag starting with 2004-04-05, a distributed Cryptomeria cipher brute force cracking effort was launched on 2003-12-21. To enforce the broadcast flag, digital video recorders employ CPRM-compatible storage devices, which the project aimed to circumvent. However, the project was ended and declared a failure on 2004-03-08 after searching the entire 56-bit keyspace, failing to turn up a valid key for unknown reasons.[3] Because the attack was based on S-box values from DVD-Audio, it was suggested that CPRM may use different S-boxes.[4]
Another brute force attack to recover DVD-Audio CPPM device keys was mounted on 2009-05-06. The attack was intended to find any of 24570 secret device keys by testing MKB file from Queen "The Game" DVD-Audio disc. On 2009-10-20 such key for column 0 and row 24408 was discovered.
The similar brute force attack to recover
By now the CPPM/CPRM protection scheme is deemed unreliable.
Notes
- ^ ISSN 0302-9743.
- ^ Darmstadt University of Technology. (Abstract is in German, rest is in English)
- ^
"Distributed C2 Brute Force Attack: Status Page". Retrieved 2006-08-14.
"C2 Brute Force Crack - team timecop". Archived version of cracking team's English web site. Archived from the original on 2005-03-06. Retrieved 2006-10-30. - ^ "Discussion about the attack (Archived)". Archived from the original on 2005-03-16. Retrieved 2006-10-30.
References
- "C2 Block Cipher Specification" (PDF). 1.0. 4C Entity, LLC. 2003-01-17. Archived from the original (PDF) on 2011-07-18. Retrieved 2009-02-13.
- "Software Obfuscation from Crackers' Viewpoint" (PDF). Proceedings of the IASTED International Conference. Puerto Vallarta, Mexico. 2006-01-23. Archived from the original (PDF) on 2007-09-26. Retrieved 2006-08-13.
