[Resource Topic] 2023/1431: Forgery Attacks on Several Beyond-Birthday-Bound Secure MACs

Welcome to the resource topic for 2023/1431

Title:
Forgery Attacks on Several Beyond-Birthday-Bound Secure MACs

Authors: Yaobin Shen, François-Xavier Standaert, Lei Wang

Abstract:

At CRYPTO’18, Datta et al. proposed nPolyMAC and proved the security up to 2^{2n/3} authentication queries and 2^{n} verification queries. At EUROCRYPT’19, Dutta et al. proposed CWC+ and showed the security up to 2^{2n/3} queries. At FSE’19, Datta et al. proposed PolyMAC and its key-reduced variant 2k-PolyMAC, and showed the security up to 2^{2n/3} queries. This security bound was then improved by Kim et al. (EUROCRYPT’20) and Datta et al (FSE’23) respectively to 2^{3n/4} and in the multi-user setting. At FSE’20, Chakraborti et al. proposed PDMMAC and 1k-PDMMAC and showed the security up to 2^{2n/3} queries. Recently, Chen et al. proposed nEHtM_p^+ and showed the security up to 2^{2n/3} queries. In this paper, we show forgery attacks on nPolyMAC, CWC+, PolyMAC, 2k-PolyMAC, PDMMAC, 1k-PDMMAC and nEHtM_p^+. Our attacks exploit some vulnerability in the underlying polynomial hash function Poly, and (i) require only one authentication query and one verification query; (ii) are nonce-respecting; (iii) succeed with probability 1. Thus, our attacks disprove the provable high security claims of these schemes. We then revisit their security analyses and identify what went wrong. Finally, we propose two solutions that can restore the beyond-birthday-bound security.

ePrint: https://eprint.iacr.org/2023/1431

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