BLAZE: Practical Lattice-Based Blind Signatures for Privacy-Preserving Applications

Blind signatures constitute basic cryptographic ingredients for privacy-preserving applications such as anonymous credentials, e-voting, and Bitcoin. Despite the great variety of cryptographic applications blind signatures also found their way in real-world scenarios. Due to the expected progress in cryptanalysis using quantum computers, it remains an important research question to find practical and secure alternatives to current systems based on the hardness of classical security assumptions such as factoring and computing discrete logarithms. In this work we present BLAZE: a new practical blind signature scheme from lattice assumptions. With respect to all relevant efficiency metrics BLAZE is more efficient than all previous blind signature schemes based on assumptions conjectured to withstand quantum computer attacks. For instance, at approximately 128 bits of security signatures are as small as 6.6KB, which represents an improvement factor of 2.7 compared to all previous candidates, and an expansion factor of 2.5 compared to the NIST PQC submission Dilithium. Our software implementation demonstrates the efficiency of BLAZE to be deployed in practical applications. In particular, generating a blind signature takes just 18 ms. The running time of both key generation and verification is in the same order as state-of-the-art ordinary signature schemes.