Cryptomeria cipher
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| Designer(s): | 4C Entity |
|---|---|
| First published: | 2003 |
| Derived from: | DES |
| Related to: | CSS |
| Key size(s): | 56 bits |
| Block size(s): | 64 bits |
| Structure: | Feistel network |
| Rounds: | 10 |
The Cryptomeria cipher, commonly referred to as C2, is a proprietary block cipher defined and licensed by the 4C Entity. It is the successor to CSS algorithm (used for DVD-Video) and was designed for the CPRM/CPPM Digital Rights Management scheme which are used by DRM-protected Secure Digital cards and DVD-Audio discs.
[edit] Cipher details
The C2 symmetric key algorithm is a 10-round Feistel cipher. Like DES, it has a key size of 56 bits and a block size of 64 bits. The encryption and decryption algorithms are available for peer review, but implementations require the so-called "secret constant", the values of the substitution boxes, which are only available under a license from the 4C Entity.
Due to the relatively short key size and straightforward implementation on unspecialized hardware, cracking the cipher through brute force utilizing commodity hardware is likely to become practical in the short term future.[citation needed] No cryptanalytic attacks on the cipher have been published as of December 2006.
[edit] 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.[1]
[edit] References
- ^ Distributed C2 Brute Force Attack: Status Page. Retrieved on August 14, 2006.
C2 Brute Force Crack - team timecop. Archived version of cracking team's English web site. Retrieved on October 30, 2006.
Discussion about the attack (Archived). Retrieved on October 30, 2006.
- (2003-01-17). "C2 Block Cipher Specification" (PDF). 1.0. 4C Entity, LLC. Retrieved on 2006-08-13.
- (2006-01-23) "Software Obfuscation from Crackers' Viewpoint" (PDF). Proceedings of the IASTED International Conference. Retrieved on 2006-08-13.
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