pqcrypto/crypto_sign/rainbowV-circumzenithal/clean/utils_hash.c

/// @file utils_hash.c
/// @brief the adapter for SHA2 families.
///
///

#include "utils_hash.h"
#include "rainbow_config.h"
#include "sha2.h"

static inline int h(unsigned char *digest, const unsigned char *m, size_t mlen) {
    sha512(digest, m, mlen);
    return 0;
}

static inline int expand_hash(unsigned char *digest, size_t n_digest, const unsigned char *hash) {
    if (_HASH_LEN >= n_digest) {
        for (size_t i = 0; i < n_digest; i++) {
            digest[i] = hash[i];
        }
        return 0;
    }
    for (size_t i = 0; i < _HASH_LEN; i++) {
        digest[i] = hash[i];
    }
    n_digest -= _HASH_LEN;

    while (_HASH_LEN <= n_digest) {
        h(digest + _HASH_LEN, digest, _HASH_LEN);

        n_digest -= _HASH_LEN;
        digest += _HASH_LEN;
    }
    unsigned char temp[_HASH_LEN];
    if (n_digest) {
        h(temp, digest, _HASH_LEN);
        for (size_t i = 0; i < n_digest; i++) {
            digest[_HASH_LEN + i] = temp[i];
        }
    }
    return 0;
}

int PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_hash_msg(unsigned char *digest,
        size_t len_digest,
        const unsigned char *m,
        size_t mlen) {
    unsigned char buf[_HASH_LEN];
    h(buf, m, mlen);
    return expand_hash(digest, len_digest, buf);
}