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MJH: A Faster Alternative to MDC2
 CTRSA 2011, LNCS 6558
, 2011
"... Abstract. In this paper, we introduce a new class of doubleblocklength hash functions. Using the ideal cipher model, we prove that these hash functions, dubbed MJH, are asymptotically collision resistant up to O(2n(1−)) query complexity for any > 0 in the iteration, where n is the block size of ..."
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Abstract. In this paper, we introduce a new class of doubleblocklength hash functions. Using the ideal cipher model, we prove that these hash functions, dubbed MJH, are asymptotically collision resistant up to O(2n(1−)) query complexity for any > 0 in the iteration, where n is the block size of the underlying blockcipher. When based on nbit key blockciphers, our construction, being of rate 1/2, provides better provable security than MDC2, the only known construction of a rate1/2 doublelength hash function based on an nbit key blockcipher with nontrivial provable security. Moreover, since key scheduling is performed only once per message block for MJH, our proposal significantly outperforms MDC2 in efficiency. When based on a 2nbit key blockcipher, we can use the extra n bits of key to increase the amount of payload accordingly. Thus we get a rate1 hash function that is much faster than existing proposals, such as TandemDM with comparable provable security. This is the full version of [19]. 1
Explicit optimal binary pebbling for oneway hash chain reversal. In: Cryptology ePrint Archive 2014/329
, 2014
"... Abstract. We present explicit optimal binary pebbling algorithms for reversing oneway hash chains. For a hash chain of length 2k, the number of hashes performed per output round is at most d k 2 e, whereas the number of hash values stored throughout is at most k. This is optimal for binary pebblin ..."
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Abstract. We present explicit optimal binary pebbling algorithms for reversing oneway hash chains. For a hash chain of length 2k, the number of hashes performed per output round is at most d k 2 e, whereas the number of hash values stored throughout is at most k. This is optimal for binary pebbling algorithms characterized by the property that the midpoint of the hash chain is computed just once and stored until it is output, and that this property applies recursively to both halves of the hash chain. We develop a framework for easy comparison of explicit binary pebbling algorithms, including simple speed1 binary pebbles, Jakobsson’s binary speed2 pebbles, and our optimal binary pebbles. Explicit schedules describe for each pebble exactly how many hashes need to be performed in each round. The optimal schedule exhibits a nice recursive structure, which allows fully optimized implementations that can readily be deployed. In particular, we develop inplace implementations with minimal storage overhead (essentially, storing only hash values), and fast implementations with minimal computational overhead. 1