How to Encipher Messages on a Small Domain
نویسندگان
چکیده
We analyze the security of the Thorp shuffle, or, equivalently, a maximally unbalanced Feistel network. Roughly said, the Thorp shuffle on N cards mixes any N1−1/r of them in O(r lgN) steps. Correspondingly, making O(r) passes of maximally unbalanced Feistel over an n-bit string ensures CCA-security to 2n(1−1/r) queries. Our results, which employ Markov-chain techniques, enable the construction of a practical and provably-secure blockcipher-based scheme for deterministically enciphering credit card numbers and the like using a conventional blockcipher. Appears in Advances in Cryptology – CRYPTO 2009
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