Abstract Recently, the concept of committing message authentication codes (MACs) was proposed at Crypto 2024, following the definition of committing authenticated encryption (AE). A secure committing MAC requires that it is infeasible for any adversary to find two different key and message pairs that generate the same tag. In this paper, we present committing attacks against PMAC, LightMAC, and UMAC, demonstrating that these MACs are not CMT secure. We also provide a CMT-K security proof for UMAC. Furthermore, we introduce two general methods for constructing one-key and two-key MACs with CMT-K security.

Abstract We present practical attacks on IAR-CTR and IAR-CFB, AE modes proposed by Hwang and Gope to offer both privacy and authenticity in a single pass. Then we use the idea of iCOFB, which is originally defined with a tweakable random function, to fix the IAR-CTR mode using the tweakable block cipher, and propose the TIAR-CTR mode, which is a one-pass AEAD mode with provable security. However, the same fixed method does not work for the IAR-CFB mode.