xmss-KAT-generator/hash.c

#include <stdint.h>
#include <string.h>
#include <openssl/sha.h>

#include "hash_address.h"
#include "xmss_commons.h"
#include "params.h"
#include "hash.h"
#include "fips202.h"

void addr_to_bytes(unsigned char *bytes, const uint32_t addr[8])
{
    int i;
    for (i = 0; i < 8; i++) {
        ull_to_bytes(bytes + i*4, 4, addr[i]);
    }
}

static int core_hash(const xmss_params *params,
                     unsigned char *out, const unsigned int type,
                     const unsigned char *key, unsigned int keylen,
                     const unsigned char *in, unsigned long long inlen, int n)
{
    unsigned char buf[inlen + n + keylen];

    /* We arrange the input into the hash function to be of the form:
     *  toByte(X, 32) || KEY || M */
    ull_to_bytes(buf, n, type);
    memcpy(buf + n, key, keylen);
    memcpy(buf + keylen + n, in, inlen);

    if (n == 32 && params->func == XMSS_SHA2) {
        SHA256(buf, inlen + keylen + n, out);
    }
    else if (n == 32 && params->func == XMSS_SHAKE) {
        shake128(out, 32, buf, inlen + keylen + n);
    }
    else if (n == 64 && params->func == XMSS_SHA2) {
        SHA512(buf, inlen + keylen + n, out);
    }
    else if (n == 64 && params->func == XMSS_SHAKE) {
        shake256(out, 64, buf, inlen + keylen + n);
    }
    else {
        return 1;
    }
    return 0;
}

int prf(const xmss_params *params,
        unsigned char *out, const unsigned char *in,
        const unsigned char *key, unsigned int keylen)
{
    return core_hash(params, out, 3, key, keylen, in, 32, keylen);
}

int h_msg(const xmss_params *params,
          unsigned char *out,
          const unsigned char *in, unsigned long long inlen,
          const unsigned char *key, const unsigned int keylen)
{
    return core_hash(params, out, 2, key, keylen, in, inlen, params->n);
}

/*
 * Computes the message hash using R, the public root, the index of the leaf
 * node, and the message. Notably, it requires m_with_prefix to have 4*n bytes
 * of space before the message, to use for the prefix. This is necessary to
 * prevent having to move the message around (and thus allocate memory for it).
 */
int hash_message(const xmss_params *params, unsigned char *out,
                 const unsigned char *R, const unsigned char *root,
                 unsigned long long idx,
                 unsigned char *m_with_prefix, unsigned long long mlen)
{
    /* We're creating a hash using input of the form:
       toByte(X, 32) || R || root || index || M */
    ull_to_bytes(m_with_prefix, params->n, 2);
    memcpy(m_with_prefix + params->n, R, params->n);
    memcpy(m_with_prefix + 2 * params->n, root, params->n);
    ull_to_bytes(m_with_prefix + 3 * params->n, params->n, idx);

    /* Since the message can be bigger than the stack, this cannot use the
     * core_hash function. */
    if (params->n == 32 && params->func == XMSS_SHA2) {
        SHA256(m_with_prefix, mlen + 4*params->n, out);
    }
    else if (params->n == 32 && params->func == XMSS_SHAKE) {
        shake128(out, 32, m_with_prefix, mlen + 4*params->n);
    }
    else if (params->n == 64 && params->func == XMSS_SHA2) {
        SHA512(m_with_prefix, mlen + 4*params->n, out);
    }
    else if (params->n == 64 && params->func == XMSS_SHAKE) {
        shake256(out, 64, m_with_prefix, mlen + 4*params->n);
    }
    else {
        return 1;
    }
    return 0;
}

/**
 * We assume the left half is in in[0]...in[n-1]
 */
int hash_h(const xmss_params *params,
           unsigned char *out, const unsigned char *in,
           const unsigned char *pub_seed, uint32_t addr[8])
{
    unsigned char buf[2*params->n];
    unsigned char key[params->n];
    unsigned char bitmask[2*params->n];
    unsigned char addr_as_bytes[32];
    unsigned int i;

    /* Generate the n-byte key. */
    set_key_and_mask(addr, 0);
    addr_to_bytes(addr_as_bytes, addr);
    prf(params, key, addr_as_bytes, pub_seed, params->n);

    /* Generate the 2n-byte mask. */
    set_key_and_mask(addr, 1);
    addr_to_bytes(addr_as_bytes, addr);
    prf(params, bitmask, addr_as_bytes, pub_seed, params->n);

    set_key_and_mask(addr, 2);
    addr_to_bytes(addr_as_bytes, addr);
    prf(params, bitmask + params->n, addr_as_bytes, pub_seed, params->n);

    for (i = 0; i < 2*params->n; i++) {
        buf[i] = in[i] ^ bitmask[i];
    }
    return core_hash(params, out, 1, key, params->n, buf, 2*params->n, params->n);
}

int hash_f(const xmss_params *params,
           unsigned char *out, const unsigned char *in,
           const unsigned char *pub_seed, uint32_t addr[8])
{
    unsigned char buf[params->n];
    unsigned char key[params->n];
    unsigned char bitmask[params->n];
    unsigned char addr_as_bytes[32];
    unsigned int i;

    set_key_and_mask(addr, 0);
    addr_to_bytes(addr_as_bytes, addr);
    prf(params, key, addr_as_bytes, pub_seed, params->n);

    set_key_and_mask(addr, 1);
    addr_to_bytes(addr_as_bytes, addr);
    prf(params, bitmask, addr_as_bytes, pub_seed, params->n);

    for (i = 0; i < params->n; i++) {
        buf[i] = in[i] ^ bitmask[i];
    }
    return core_hash(params, out, 0, key, params->n, buf, params->n, params->n);
}