## Cryptology ePrint Archive: Report 2009/168

A Second Pre-image Attack Against Elliptic Curve Only Hash (ECOH)

Michael A. Halcrow and Niels Ferguson

Abstract: We present a second pre-image attack on ECOH. Our attack requires $2^{143}$ time for ECOH-224 and ECOH-256, $2^{206}$ time for ECOH-384, and $2^{287}$ time for ECOH-512. The attack sets the checksum block to a fixed value and uses a collision search on the elliptic curve points.

Category / Keywords: secret-key cryptography / ECOH cryptanalysis