## Cryptology ePrint Archive: Report 2016/225

A New Birthday-Type Algorithm for Attacking the Fresh Re-Keying Countermeasure

Qian Guo, and Thomas Johansson

Abstract: The fresh re-keying scheme is a countermeasure designed to protect low-cost devices against side-channel attacks. In this paper, we present a new birthday-type attack based on a refined reduction to Ring-LPN with a reducible polynomial. Compared with the previous research, our algorithm significantly reduces the time complexity in the 128-bit leakage model—with an SNR equal to 8 and at most $2^{20}$ traces, for instance, the key can be recovered using $2^{41.99}$ bit-operations.

Category / Keywords: secret-key cryptography / LPN, Ring-LPN, fresh re-keying, birthday attacks