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Mercy: a fast large block cipher for disk sector encryption

Paul Crowley

Date: April 2000


We discuss the special requirements imposed on the underlying cipher of systems which encrypt each sector of a disk partition independently, and demonstrate a certificational weakness in some existing block ciphers including Bellare and Rogaway's 1999 proposal, proposing a new quantitative measure of avalanche. To address these needs, we present Mercy, a new block cipher accepting large (4096-bit) blocks, which uses a key-dependent state machine to build a bijective F function for a Feistel cipher. Mercy achieves 9 cycles/byte on a Pentium compatible processor.
Key words: disk sector, large block, state machine, avalanche, Feistel cipher.
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