Paper 2021/1298 Original: eprint.iacr.org/2021/1298 ↗

Post-Quantum Authentication with Lightweight Cryptographic Primitives

Abstract

We propose to adapt ”low-algebra” digital signature schemes SPHINCS+ and PICNIC, present in the NIST-PQC contest, to the limitations of resource-bounded low-end devices. For this, we replaced the cryptographic primitives (hash functions and symmetric ciphers) of these schemes with lightweight alternatives presented in the NIST-LWC contest. With these specifically conceived primitives, we improve the performance of the signature schemes and still preserve the NIST’s security levels. Regarding SPHINCS+, besides replacing the hash function, we also take into consideration relaxing some parameters and introduce a new notion: security as life expectancy. Furthermore, we also introduce an attack to the SPHINCS+ scheme that takes advantage of the usage of FORS on this scheme and the way its leaves are calculated. Also, we give some solutions on how to avoid this attack. Additionally, a modification of PICNIC is introduced as PICNIC+WOTS where PICNIC is used to generate the secret keys for several WOTS+ signatures significantly reducing the size and signature time of each signature.