Paper 2019/888

Weak Keys in the Rekeying Paradigm: Attacks on COMET-128 and mixFeed

Mustafa Khairallah

Abstract

In this article, we analyze two of the NIST Round 1 Candidates for the Lightweight Cryptography Standardization Process: COMET and mixFeed. We show how AEAD modes that are based on rekeying can be modelled as modes without rekeying in the multi-key setting, where every nonce is treated as a different user. Then we show that the security degradation due to weak keys in the multi-key setting will affect these modes in the single key setting. We show how the weak key analysis of both these modes may be applied.