Toru Owada

A lightweight 256-bit hash function for hardware and low-end devices: lesamnta-LW

This paper proposes a new lightweight 256-bit hash function Lesamnta-LW with claimed security levels of at least 2120 with respect to collision, preimage, and second preimage attacks. We adopt the Merkle-Damgard domain extension; the compression function is constructed from a dedicated AES-based block cipher using the LW1 mode, for which a security reduction can be proven. In terms of lightweight implementations, Lesamnta-LW offers a competitive advantage over other 256-bit hash functions. Our size-optimized hardware implementation of Lesamnta-LW requires only 8.24 Kgates on 90 nm technology. Our software implementation of Lesamnta-LW requires only 50 bytes of RAM and runs fast on short messages on 8-bit CPUs.

Update on Enocoro stream cipher

Enocoro is a family of stream ciphers proposed by Watanabe et al. in 2007. It consists of two algorithms called Enocoro-80 and Enocoro-128v1.1, whose key lengths are 80 bits and 128 bits respectively. In this paper, we show that Enocoro-128v1.1 is vulnerable against the related-key attack in which we assume a stronger attacker than one in the related-key differential attack. The attack is applicable with 2112 out of 2128 keys and the calculation complexity of the attack is about 265. Our attack is mainly of theoretical interest and do not present a threat to practical applications using Enocoro-128v1.1. In addition, we propose to update Enocoro-128v1.1 to Enocoro-128v2 where a patch has been applied to prevent the attack.