ref: 94f2907dc40a6415a10c252cb9ba3971f1f7e838
dir: /third_party/boringssl/src/crypto/spx/spx_fors.c/
/* Copyright (c) 2023, Google LLC
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
#include <openssl/base.h>
#include <string.h>
#include "./spx_address.h"
#include "./spx_fors.h"
#include "./spx_params.h"
#include "./spx_util.h"
#include "./spx_thash.h"
void spx_fors_sk_gen(uint8_t *fors_sk, uint32_t idx,
const uint8_t sk_seed[SPX_N], const uint8_t pk_seed[SPX_N],
uint8_t addr[32]) {
uint8_t sk_addr[32];
memcpy(sk_addr, addr, sizeof(sk_addr));
spx_set_type(sk_addr, SPX_ADDR_TYPE_FORSPRF);
spx_copy_keypair_addr(sk_addr, addr);
spx_set_tree_index(sk_addr, idx);
spx_thash_prf(fors_sk, pk_seed, sk_seed, sk_addr);
}
void spx_fors_treehash(uint8_t root_node[SPX_N], const uint8_t sk_seed[SPX_N],
uint32_t i /*target node index*/,
uint32_t z /*target node height*/,
const uint8_t pk_seed[SPX_N], uint8_t addr[32]) {
BSSL_CHECK(z <= SPX_FORS_HEIGHT);
BSSL_CHECK(i < (uint32_t)(SPX_FORS_TREES * (1 << (SPX_FORS_HEIGHT - z))));
if (z == 0) {
uint8_t sk[SPX_N];
spx_set_tree_height(addr, 0);
spx_set_tree_index(addr, i);
spx_fors_sk_gen(sk, i, sk_seed, pk_seed, addr);
spx_thash_f(root_node, sk, pk_seed, addr);
} else {
// Stores left node and right node.
uint8_t nodes[2 * SPX_N];
spx_fors_treehash(nodes, sk_seed, 2 * i, z - 1, pk_seed, addr);
spx_fors_treehash(nodes + SPX_N, sk_seed, 2 * i + 1, z - 1, pk_seed, addr);
spx_set_tree_height(addr, z);
spx_set_tree_index(addr, i);
spx_thash_h(root_node, nodes, pk_seed, addr);
}
}
void spx_fors_sign(uint8_t *fors_sig, const uint8_t message[SPX_FORS_MSG_BYTES],
const uint8_t sk_seed[SPX_N], const uint8_t pk_seed[SPX_N],
uint8_t addr[32]) {
uint32_t indices[SPX_FORS_TREES];
// Derive FORS indices compatible with the NIST changes.
spx_base_b(indices, SPX_FORS_TREES, message, /*log2_b=*/SPX_FORS_HEIGHT);
for (size_t i = 0; i < SPX_FORS_TREES; ++i) {
spx_set_tree_height(addr, 0);
// Write the FORS secret key element to the correct position.
spx_fors_sk_gen(fors_sig + i * SPX_N * (SPX_FORS_HEIGHT + 1),
i * (1 << SPX_FORS_HEIGHT) + indices[i], sk_seed, pk_seed,
addr);
for (size_t j = 0; j < SPX_FORS_HEIGHT; ++j) {
size_t s = (indices[i] / (1 << j)) ^ 1;
// Write the FORS auth path element to the correct position.
spx_fors_treehash(fors_sig + SPX_N * (i * (SPX_FORS_HEIGHT + 1) + j + 1),
sk_seed, i * (1ULL << (SPX_FORS_HEIGHT - j)) + s, j,
pk_seed, addr);
}
}
}
void spx_fors_pk_from_sig(uint8_t *fors_pk,
const uint8_t fors_sig[SPX_FORS_BYTES],
const uint8_t message[SPX_FORS_MSG_BYTES],
const uint8_t pk_seed[SPX_N], uint8_t addr[32]) {
uint32_t indices[SPX_FORS_TREES];
uint8_t tmp[2 * SPX_N];
uint8_t roots[SPX_FORS_TREES * SPX_N];
// Derive FORS indices compatible with the NIST changes.
spx_base_b(indices, SPX_FORS_TREES, message, /*log2_b=*/SPX_FORS_HEIGHT);
for (size_t i = 0; i < SPX_FORS_TREES; ++i) {
// Pointer to current sk and authentication path
const uint8_t *sk = fors_sig + i * SPX_N * (SPX_FORS_HEIGHT + 1);
const uint8_t *auth = fors_sig + i * SPX_N * (SPX_FORS_HEIGHT + 1) + SPX_N;
uint8_t nodes[2 * SPX_N];
spx_set_tree_height(addr, 0);
spx_set_tree_index(addr, (i * (1 << SPX_FORS_HEIGHT)) + indices[i]);
spx_thash_f(nodes, sk, pk_seed, addr);
for (size_t j = 0; j < SPX_FORS_HEIGHT; ++j) {
spx_set_tree_height(addr, j + 1);
// Even node
if (((indices[i] / (1 << j)) % 2) == 0) {
spx_set_tree_index(addr, spx_get_tree_index(addr) / 2);
memcpy(tmp, nodes, SPX_N);
memcpy(tmp + SPX_N, auth + j * SPX_N, SPX_N);
spx_thash_h(nodes + SPX_N, tmp, pk_seed, addr);
} else {
spx_set_tree_index(addr, (spx_get_tree_index(addr) - 1) / 2);
memcpy(tmp, auth + j * SPX_N, SPX_N);
memcpy(tmp + SPX_N, nodes, SPX_N);
spx_thash_h(nodes + SPX_N, tmp, pk_seed, addr);
}
memcpy(nodes, nodes + SPX_N, SPX_N);
}
memcpy(roots + i * SPX_N, nodes, SPX_N);
}
uint8_t forspk_addr[32];
memcpy(forspk_addr, addr, sizeof(forspk_addr));
spx_set_type(forspk_addr, SPX_ADDR_TYPE_FORSPK);
spx_copy_keypair_addr(forspk_addr, addr);
spx_thash_tk(fors_pk, roots, pk_seed, forspk_addr);
}