CRYPTOMERIA CIPHER

Cryptomeria cipher
The Feistel function of the Cryptomeria cipher algorithm
General
Designer(s)	4C Entity
First published	2003
Derived from	DES (?)
Cipher(s) based on this design	none
Algorithm detail
Block size(s)	64 bits
Key size(s)	56 bits
Structure	Feistel network
Number of rounds	10
Best cryptanalysis

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.

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]}

This cryptography-related article is a stub. You can help Wikipedia by expanding it.

Distributed brute force cracking effort

Following an announcement by Japanese HDTV broadcasts 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 ended on 2004-03-08 after searching the entire 56-bit keyspace. For unknown reasons, the attempt did not turn up a valid key for unknown reasons and was declared a failure.^[1]

References

1. ^ C2 Brute Force Crack - team timecop. A cracking team's English web site. Retrieved on 2006-08-14.
   Distributed C2 Brute Force Attack: Status Page. Retrieved on 2006-08-14.
   Discussion about the attack. Retrieved on 2006-08-14.

• (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.