TY - GEN

T1 - Merkle-damgård revisited

T2 - 25th Annual International Cryptology Conference, CRYPTO 2005

AU - Coron, Jean Sébastien

AU - Dodis, Yevgeniy

AU - Malinaud, Cécile

AU - Puniya, Prashant

PY - 2006

Y1 - 2006

N2 - The most common way of constructing a hash function (e.g., SHA-1) is to iterate a compression function on the input message, The compression function is usually designed from scratch or made out of a block-cipher. In this paper, we introduce a new security notion for hash-functions, stronger than collision-resistance. Under this notion, the arbitrary length hash function H must behave as a random oracle when the fixed-length building block is viewed as a random oracle or an ideal block-cipher. The key property is that if a particular construction meets this definition, then any cryptosystem proven secure assuming H is a random oracle remains secure if one plugs in this construction (still assuming that the underlying fixed-length primitive is ideal). In this paper, we show that the current design principle behind hash functions such as SHA-1 and MD5 - the (strengthened) Merkle-Damgård transformation - does not satisfy this security notion. We provide several constructions that provably satisfy this notion; those new constructions introduce minimal changes to the plain Merkle-Damgård construction and are easily implementable in practice.

AB - The most common way of constructing a hash function (e.g., SHA-1) is to iterate a compression function on the input message, The compression function is usually designed from scratch or made out of a block-cipher. In this paper, we introduce a new security notion for hash-functions, stronger than collision-resistance. Under this notion, the arbitrary length hash function H must behave as a random oracle when the fixed-length building block is viewed as a random oracle or an ideal block-cipher. The key property is that if a particular construction meets this definition, then any cryptosystem proven secure assuming H is a random oracle remains secure if one plugs in this construction (still assuming that the underlying fixed-length primitive is ideal). In this paper, we show that the current design principle behind hash functions such as SHA-1 and MD5 - the (strengthened) Merkle-Damgård transformation - does not satisfy this security notion. We provide several constructions that provably satisfy this notion; those new constructions introduce minimal changes to the plain Merkle-Damgård construction and are easily implementable in practice.

UR - http://www.scopus.com/inward/record.url?scp=33745119040&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33745119040&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:33745119040

SN - 3540281142

SN - 9783540281146

T3 - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

SP - 430

EP - 448

BT - Advances in Cryptology - CRYPTO 2005 - 25th Annual International Cryptology Conference, Proceedings

Y2 - 14 August 2005 through 18 August 2005

ER -