Key-Schedule Cryptanalysis of DEAL
نویسندگان
چکیده
DEAL is a sixor eight-round Luby-Rackoff cipher that uses DES as its round function, with allowed key lengths of 128, 192, and 256 bits. In this paper, we discuss two new results on the DEAL key schedule. First, we discuss the existence of equivalent keys for all three key lengths; pairs of equivalent keys in DEAL-128 require about 2 DES encryptions to find, while equivalent keys in DEAL-192 and DEAL-256 require only six or eight DES encryptions to find. Second, we discuss a new related-key attack on DEAL-192 and DEAL256. This attack requires 2 related key queries, the same 3 plaintexts encrypted under each key, and may be implemented with a variety of time-memory tradeoffs; Given 3 × 2 bytes of memory, the attack requires 2 DES encryptions, and given 3× 2 bytes of memory, the attack requires 2 DES encryptions. We conclude with some questions raised by the analysis.
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