eyalr0/sphincsplusc

This repository contains the software for the SPHINCS+C scheme

SPHINCS+C

This repository contains the software for the SPHINCS+C scheme.

It is based on the SPHINCS+ submission repository that contains the software that accompanies the SPHINCS+ submission to NIST's Post-Quantum Cryptography project.

Currently, only the reference implementation for shake is supported.

Parameters

The SPHINCS+C scheme presents several novel methods for further compressing the signature size of SPHICS+ while requiring negligible added computational costs for the signer and faster verification time. Like SPHINCS+, we present named instances for specific hash functions and concrete parameters for the security level, tree dimensions, WOTS+C, and FORS+C. This reference implementation allows for more flexibility, as parameters can be specified in a params.h file. The proposed parameter sets have been predefined in ref/params/params-*.h, and the hash function can be varied by linking with the different implementations of hash.h, i.e., hash_haraka.c, hash_sha2.c and hash_shake.c, as well as different implementations of thash.h, i.e., *_robust.c and *_simple.c. This is demonstrated in the Makefile. Note that only variants based on the reference SHAKE implementation are currently supported. See the table below for a summary of the parameter sets. These parameters target the NIST security categories 1, 3, and 5; each category has a parameter set geared towards either small signatures or fast signature generation.

	n	h	d	log(t)	k	w	log(t')	bit security	pk bytes	sk bytes	sig bytes
SPHINCS+-128s	16	66	11	13	9	128	18	128	32	64	6,304
SPHINCS+-128f	16	63	21	9	19	16	8	128	32	64	14,904
SPHINCS+-192s	24	66	11	15	13	128	12	192	48	96	13,776
SPHINCS+-192f	24	66	22	9	25	16	13	192	48	96	33,044
SPHINCS+-256s	32	66	11	14	19	64	19	256	64	128	26,096
SPHINCS+-256f	32	64	16	10	33	16	10	256	64	128	46,884

License

Following the original code from the SPHINCS+ submission repository, all included code is available under the CC0 1.0 Universal Public Domain Dedication, with the exception of rng.c, rng.h and PQCgenKAT_sign.c, which were provided by NIST.

Acknowledgments

We thank Ofek Bransky for his contribution to the implementation and benchmark of the code.

sphincsplusc's Issues

how to understand the condition for wots+c counter?

I want to commend your work, but there is something I don't understand in the process of reading the code: when searching for the counter of wots+c, what is the basis for meeting this condition? According to your article, it should be $\forall i \in[z]: a_i=0$. I hope to receive your explanation. Thank you!

the picture from the file in ref/merkle.c