Paper 2024/1325

Authenticity in the Presence of Leakage using a Forkcipher

Abstract

Robust message authentication codes (MACs) and authenticated encryption (AE) schemes that provide authenticity in the presence of side-channel leakage are essential primitives. These constructions often rely on primitives designed for strong leakage protection, among others including the use of strong-unpredictable (tweakable) block-ciphers. This paper extends the strong-unpredictability security definition to the versatile and new forkcipher primitive. We show how to construct secure and efficient MAC and AEs that guarantee authenticity in the presence of leakage. We present a leakage-resistant MAC, ForkMAC, and two leakage-resistant AE schemes, ForkDTE1 and ForkDTE2, which use forkciphers instead of traditional secure (tweakable) block-ciphers as compared to the prior art. We prove and analyze their security in the presence of leakage based on a strong unpredictable forkcipher. A comparison with the state-of-the-art in terms of both security and efficiency is followed in the paper. Key advantages and highlights promoted by the proposed constructions are that for the minimal assumptions they require, unpredictability with leakage-based security, the tag-generation of ForkMAC is the most efficient among leakage-resilient MAC proposals, equivalent to HBC. ForkDTE 1 and 2 have a more efficient encryption than any other scheme, achieving integrity with leakage (and also providing misuse-resistance).