#include <stdint.h> #include <string.h> #include "address.h" #include "hash.h" #include "hash_state.h" #include "params.h" #include "thash.h" #include "utils.h" #include "wots.h" // TODO clarify address expectations, and make them more uniform. // TODO i.e. do we expect types to be set already? // TODO and do we expect modifications or copies? /** * Computes the starting value for a chain, i.e. the secret key. * Expects the address to be complete up to the chain address. */ static void wots_gen_sk(unsigned char *sk, const unsigned char *sk_seed, uint32_t wots_addr[8], const hash_state *hash_state_seeded) { /* Make sure that the hash address is actually zeroed. */ PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_set_hash_addr(wots_addr, 0); /* Generate sk element. */ PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_prf_addr(sk, sk_seed, wots_addr, hash_state_seeded); } /** * Computes the chaining function. * out and in have to be n-byte arrays. * * Interprets in as start-th value of the chain. * addr has to contain the address of the chain. */ static void gen_chain(unsigned char *out, const unsigned char *in, unsigned int start, unsigned int steps, const unsigned char *pub_seed, uint32_t addr[8], const hash_state *hash_state_seeded) { uint32_t i; /* Initialize out with the value at position 'start'. */ memcpy(out, in, PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N); /* Iterate 'steps' calls to the hash function. */ for (i = start; i < (start + steps) && i < PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_W; i++) { PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_set_hash_addr(addr, i); PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_thash_1( out, out, pub_seed, addr, hash_state_seeded); } } /** * base_w algorithm as described in draft. * Interprets an array of bytes as integers in base w. * This only works when log_w is a divisor of 8. */ static void base_w(unsigned int *output, const size_t out_len, const unsigned char *input) { size_t in = 0; size_t out = 0; unsigned char total = 0; unsigned int bits = 0; size_t consumed; for (consumed = 0; consumed < out_len; consumed++) { if (bits == 0) { total = input[in]; in++; bits += 8; } bits -= PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LOGW; output[out] = (unsigned int)((total >> bits) & (PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_W - 1)); out++; } } /* Computes the WOTS+ checksum over a message (in base_w). */ static void wots_checksum(unsigned int *csum_base_w, const unsigned int *msg_base_w) { unsigned int csum = 0; unsigned char csum_bytes[(PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN2 * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LOGW + 7) / 8]; unsigned int i; /* Compute checksum. */ for (i = 0; i < PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN1; i++) { csum += PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_W - 1 - msg_base_w[i]; } /* Convert checksum to base_w. */ /* Make sure expected empty zero bits are the least significant bits. */ csum = csum << (8 - ((PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN2 * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LOGW) % 8)); PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_ull_to_bytes( csum_bytes, sizeof(csum_bytes), csum); base_w(csum_base_w, PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN2, csum_bytes); } /* Takes a message and derives the matching chain lengths. */ static void chain_lengths(unsigned int *lengths, const unsigned char *msg) { base_w(lengths, PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN1, msg); wots_checksum(lengths + PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN1, lengths); } /** * WOTS key generation. Takes a 32 byte sk_seed, expands it to WOTS private key * elements and computes the corresponding public key. * It requires the seed pub_seed (used to generate bitmasks and hash keys) * and the address of this WOTS key pair. * * Writes the computed public key to 'pk'. */ void PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_wots_gen_pk( unsigned char *pk, const unsigned char *sk_seed, const unsigned char *pub_seed, uint32_t addr[8], const hash_state *hash_state_seeded) { uint32_t i; for (i = 0; i < PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN; i++) { PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_set_chain_addr(addr, i); wots_gen_sk(pk + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, sk_seed, addr, hash_state_seeded); gen_chain(pk + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, pk + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, 0, PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_W - 1, pub_seed, addr, hash_state_seeded); } } /** * Takes a n-byte message and the 32-byte sk_see to compute a signature 'sig'. */ void PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_wots_sign( unsigned char *sig, const unsigned char *msg, const unsigned char *sk_seed, const unsigned char *pub_seed, uint32_t addr[8], const hash_state *hash_state_seeded) { unsigned int lengths[PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN]; uint32_t i; chain_lengths(lengths, msg); for (i = 0; i < PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN; i++) { PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_set_chain_addr(addr, i); wots_gen_sk(sig + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, sk_seed, addr, hash_state_seeded); gen_chain(sig + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, sig + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, 0, lengths[i], pub_seed, addr, hash_state_seeded); } } /** * Takes a WOTS signature and an n-byte message, computes a WOTS public key. * * Writes the computed public key to 'pk'. */ void PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_wots_pk_from_sig( unsigned char *pk, const unsigned char *sig, const unsigned char *msg, const unsigned char *pub_seed, uint32_t addr[8], const hash_state *hash_state_seeded) { unsigned int lengths[PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN]; uint32_t i; chain_lengths(lengths, msg); for (i = 0; i < PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_LEN; i++) { PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_set_chain_addr(addr, i); gen_chain(pk + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, sig + i * PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_N, lengths[i], PQCLEAN_SPHINCSSHAKE256128FSIMPLE_CLEAN_WOTS_W - 1 - lengths[i], pub_seed, addr, hash_state_seeded); } }