Cryptanalysis of C2
نویسندگان
چکیده
We present several attacks on the block cipher C2, which is used for encrypting DVD Audio discs and Secure Digital cards. C2 has a 56 bit key and a secret 8 to 8 bit S-box. We show that if the attacker is allowed to choose the key, the S-box can be recovered in 2 C2 encryptions. Attacking the 56 bit key for a known S-box can be done in complexity 2. Finally, a C2 implementation with a 8 to 8 bit secret S-box (equivalent to 2048 secret bits) and a 56 bit secret key can be attacked in 2 C2 encryptions on average.
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