Related-key rectangle attack of the full HAS-160 encryption mode

Abstract

In this paper we investigate the security of the encryption mode of the HAS-160 hash function. HAS-160 is a Korean hash standard which is widely used in Korean industry. The structure of HAS-160 is similar to SHA-1 besides some modifications. In this paper, we present the first cryptographic attack that breaks the encryption mode of the full 80-round HAS-160. SHACAL-1 and the encryption mode of HAS-160 are both blockciphers with key size 512 bits and plain-/ciphertext size of 160 bits. We apply a key recovery attack that needs about 2155 chosen plaintexts and 2377.5 80-round HAS-160 encryptions. The attack does not aim for a collision, preimage or 2nd-preimage attack, but it shows that HAS-160 used as a block cipher can be differentiated from an ideal cipher faster than exhaustive search. © 2009 Springer-Verlag.