SPHINCS is a stateless hash-based signature scheme, which is quantum robust. It was proposed by Bernstein et al. in 2015 [paper] and updated in [1]. SPHINCS+ 256 128-bit has a public key size of 32 bytes, a private key size of 64 bytes, and a signature of 17KB. It has been shown to operate at speeds of hundreds of hashes per second on a 4-core 3.5GHz processor. In this case we will implement using SHA-256. Other hashing methods are Haraka and SHAKE-256, for 128-bit, 192-bit and 256-bit versions [article].
Method Public key size Private key size Signature size Security level ------------------------------------------------------------------------------------------------------ SPHINCS+ SHA-256 128-bit 32 64 17,088 1 (128-bit) SPHINCS+ SHA-256 192-bit 48 96 35,664 3 (192-bit) SPHINCS+ SHA-256 256-bit 64 128 49,856 5 (256-bit)
Related: [Kyber KEM][Kyber KEX][Dilithium Dig Sig Speed][Factoring signature (ECC)][Factoring signature (Logs)][Falcon Digital Signature][Rainbow Digital Signature][Dilithium Digital Signature][SPHINCS+][GeMSS]