Note on the Robustness of CAESAR Candidates

Authenticated ciphers rely on the uniqueness of the nonces to meet their security goals. In this work, we investigate the implications of reusing nonces for three third-round candidates of the ongoing CAESAR competition, namely Tiaoxin, AEGIS and MORUS. We show that an attacker that is able to force nonces to be reused can reduce the security of the ciphers with results ranging from full key-recovery to forgeries with practical complexity and a very low number of nonce-misuse queries.