237 行
8.0 KiB
C
237 行
8.0 KiB
C
#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#include "hash.h"
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#include "hash_address.h"
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#include "params.h"
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#include "wots.h"
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#include "utils.h"
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#include "xmss_commons.h"
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/**
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* Computes a leaf node from a WOTS public key using an L-tree.
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* Note that this destroys the used WOTS public key.
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*/
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static void l_tree(const xmss_params *params,
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unsigned char *leaf, unsigned char *wots_pk,
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const unsigned char *pub_seed, uint32_t addr[8])
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{
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unsigned int l = params->wots_len;
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unsigned int parent_nodes;
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uint32_t i;
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uint32_t height = 0;
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set_tree_height(addr, height);
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while (l > 1) {
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parent_nodes = l >> 1;
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for (i = 0; i < parent_nodes; i++) {
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set_tree_index(addr, i);
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/* Hashes the nodes at (i*2)*params->n and (i*2)*params->n + 1 */
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thash_h(params, wots_pk + i*params->n,
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wots_pk + (i*2)*params->n, pub_seed, addr);
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}
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/* If the row contained an odd number of nodes, the last node was not
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hashed. Instead, we pull it up to the next layer. */
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if (l & 1) {
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memcpy(wots_pk + (l >> 1)*params->n,
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wots_pk + (l - 1)*params->n, params->n);
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l = (l >> 1) + 1;
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}
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else {
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l = l >> 1;
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}
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height++;
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set_tree_height(addr, height);
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}
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memcpy(leaf, wots_pk, params->n);
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}
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/**
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* Computes a root node given a leaf and an auth path
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*/
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static void compute_root(const xmss_params *params, unsigned char *root,
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const unsigned char *leaf, unsigned long leafidx,
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const unsigned char *auth_path,
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const unsigned char *pub_seed, uint32_t addr[8])
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{
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uint32_t i;
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unsigned char buffer[2*params->n];
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/* If leafidx is odd (last bit = 1), current path element is a right child
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and auth_path has to go left. Otherwise it is the other way around. */
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if (leafidx & 1) {
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memcpy(buffer + params->n, leaf, params->n);
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memcpy(buffer, auth_path, params->n);
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}
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else {
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memcpy(buffer, leaf, params->n);
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memcpy(buffer + params->n, auth_path, params->n);
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}
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auth_path += params->n;
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for (i = 0; i < params->tree_height - 1; i++) {
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set_tree_height(addr, i);
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leafidx >>= 1;
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set_tree_index(addr, leafidx);
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/* Pick the right or left neighbor, depending on parity of the node. */
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if (leafidx & 1) {
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thash_h(params, buffer + params->n, buffer, pub_seed, addr);
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memcpy(buffer, auth_path, params->n);
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}
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else {
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thash_h(params, buffer, buffer, pub_seed, addr);
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memcpy(buffer + params->n, auth_path, params->n);
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}
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auth_path += params->n;
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}
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/* The last iteration is exceptional; we do not copy an auth_path node. */
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set_tree_height(addr, params->tree_height - 1);
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leafidx >>= 1;
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set_tree_index(addr, leafidx);
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thash_h(params, root, buffer, pub_seed, addr);
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}
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/**
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* Computes the leaf at a given address. First generates the WOTS key pair,
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* then computes leaf using l_tree. As this happens position independent, we
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* only require that addr encodes the right ltree-address.
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*/
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void gen_leaf_wots(const xmss_params *params, unsigned char *leaf,
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const unsigned char *sk_seed, const unsigned char *pub_seed,
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uint32_t ltree_addr[8], uint32_t ots_addr[8])
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{
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unsigned char seed[params->n];
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unsigned char pk[params->wots_sig_bytes];
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get_seed(params, seed, sk_seed, ots_addr);
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wots_pkgen(params, pk, seed, pub_seed, ots_addr);
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l_tree(params, leaf, pk, pub_seed, ltree_addr);
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}
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/**
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* Used for pseudo-random key generation.
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* Generates the seed for the WOTS key pair at address 'addr'.
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*
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* Takes n-byte sk_seed and returns n-byte seed using 32 byte address 'addr'.
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*/
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void get_seed(const xmss_params *params, unsigned char *seed,
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const unsigned char *sk_seed, uint32_t addr[8])
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{
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unsigned char bytes[32];
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/* Make sure that chain addr, hash addr, and key bit are zeroed. */
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set_chain_addr(addr, 0);
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set_hash_addr(addr, 0);
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set_key_and_mask(addr, 0);
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/* Generate seed. */
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addr_to_bytes(bytes, addr);
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prf(params, seed, bytes, sk_seed);
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}
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/**
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* Verifies a given message signature pair under a given public key.
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* Note that this assumes a pk without an OID, i.e. [root || PUB_SEED]
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*/
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int xmss_core_sign_open(const xmss_params *params,
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unsigned char *m, unsigned long long *mlen,
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const unsigned char *sm, unsigned long long smlen,
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const unsigned char *pk)
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{
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/* XMSS signatures are fundamentally an instance of XMSSMT signatures.
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For d=1, as is the case with XMSS, some of the calls in the XMSSMT
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routine become vacuous (i.e. the loop only iterates once, and address
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management can be simplified a bit).*/
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return xmssmt_core_sign_open(params, m, mlen, sm, smlen, pk);
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}
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/**
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* Verifies a given message signature pair under a given public key.
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* Note that this assumes a pk without an OID, i.e. [root || PUB_SEED]
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*/
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int xmssmt_core_sign_open(const xmss_params *params,
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unsigned char *m, unsigned long long *mlen,
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const unsigned char *sm, unsigned long long smlen,
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const unsigned char *pk)
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{
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const unsigned char *pub_root = pk;
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const unsigned char *pub_seed = pk + params->n;
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unsigned char wots_pk[params->wots_sig_bytes];
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unsigned char leaf[params->n];
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unsigned char root[params->n];
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unsigned char *mhash = root;
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unsigned long long idx = 0;
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unsigned int i;
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uint32_t idx_leaf;
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uint32_t ots_addr[8] = {0};
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uint32_t ltree_addr[8] = {0};
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uint32_t node_addr[8] = {0};
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set_type(ots_addr, XMSS_ADDR_TYPE_OTS);
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set_type(ltree_addr, XMSS_ADDR_TYPE_LTREE);
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set_type(node_addr, XMSS_ADDR_TYPE_HASHTREE);
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*mlen = smlen - params->sig_bytes;
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/* Convert the index bytes from the signature to an integer. */
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idx = bytes_to_ull(sm, params->index_bytes);
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/* Put the message all the way at the end of the m buffer, so that we can
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* prepend the required other inputs for the hash function. */
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memcpy(m + params->sig_bytes, sm + params->sig_bytes, *mlen);
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/* Compute the message hash. */
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hash_message(params, mhash, sm + params->index_bytes, pk, idx,
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m + params->sig_bytes - 4*params->n, *mlen);
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sm += params->index_bytes + params->n;
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/* For each subtree.. */
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for (i = 0; i < params->d; i++) {
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idx_leaf = (idx & ((1 << params->tree_height)-1));
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idx = idx >> params->tree_height;
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set_layer_addr(ots_addr, i);
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set_layer_addr(ltree_addr, i);
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set_layer_addr(node_addr, i);
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set_tree_addr(ltree_addr, idx);
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set_tree_addr(ots_addr, idx);
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set_tree_addr(node_addr, idx);
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/* The WOTS public key is only correct if the signature was correct. */
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set_ots_addr(ots_addr, idx_leaf);
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/* Initially, root = mhash, but on subsequent iterations it is the root
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of the subtree below the currently processed subtree. */
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wots_pk_from_sig(params, wots_pk, sm, root, pub_seed, ots_addr);
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sm += params->wots_sig_bytes;
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/* Compute the leaf node using the WOTS public key. */
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set_ltree_addr(ltree_addr, idx_leaf);
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l_tree(params, leaf, wots_pk, pub_seed, ltree_addr);
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/* Compute the root node of this subtree. */
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compute_root(params, root, leaf, idx_leaf, sm, pub_seed, node_addr);
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sm += params->tree_height*params->n;
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}
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/* Check if the root node equals the root node in the public key. */
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if (memcmp(root, pub_root, params->n)) {
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/* If not, zero the message */
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memset(m, 0, *mlen);
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*mlen = 0;
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return -1;
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}
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/* If verification was successful, copy the message from the signature. */
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memcpy(m, sm, *mlen);
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return 0;
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}
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