/* $OpenBSD: xmss_fast.c,v 1.2 2018/02/26 03:56:44 dtucker Exp $ */ /* xmss_fast.c version 20160722 Andreas Hülsing Joost Rijneveld Public domain. */ #include "includes.h" #ifdef WITH_XMSS #include "xmss_fast.h" #include <stdlib.h> #include <string.h> #ifdef HAVE_STDINT_H #include <stdint.h> #endif #include "crypto_api.h" #include "xmss_wots.h" #include "xmss_hash.h" #include "xmss_commons.h" #include "xmss_hash_address.h" // For testing #include "stdio.h" /** * Used for pseudorandom keygeneration, * generates the seed for the WOTS keypair at address addr * * takes n byte sk_seed and returns n byte seed using 32 byte address addr. */ static void get_seed(unsigned char *seed, const unsigned char *sk_seed, int n, uint32_t addr[8]) { unsigned char bytes[32]; // Make sure that chain addr, hash addr, and key bit are 0! setChainADRS(addr,0); setHashADRS(addr,0); setKeyAndMask(addr,0); // Generate pseudorandom value addr_to_byte(bytes, addr); prf(seed, bytes, sk_seed, n); } /** * Initialize xmss params struct * parameter names are the same as in the draft * parameter k is K as used in the BDS algorithm */ int xmss_set_params(xmss_params *params, int n, int h, int w, int k) { if (k >= h || k < 2 || (h - k) % 2) { fprintf(stderr, "For BDS traversal, H - K must be even, with H > K >= 2!\n"); return 1; } params->h = h; params->n = n; params->k = k; wots_params wots_par; wots_set_params(&wots_par, n, w); params->wots_par = wots_par; return 0; } /** * Initialize BDS state struct * parameter names are the same as used in the description of the BDS traversal */ void xmss_set_bds_state(bds_state *state, unsigned char *stack, int stackoffset, unsigned char *stacklevels, unsigned char *auth, unsigned char *keep, treehash_inst *treehash, unsigned char *retain, int next_leaf) { state->stack = stack; state->stackoffset = stackoffset; state->stacklevels = stacklevels; state->auth = auth; state->keep = keep; state->treehash = treehash; state->retain = retain; state->next_leaf = next_leaf; } /** * Initialize xmssmt_params struct * parameter names are the same as in the draft * * Especially h is the total tree height, i.e. the XMSS trees have height h/d */ int xmssmt_set_params(xmssmt_params *params, int n, int h, int d, int w, int k) { if (h % d) { fprintf(stderr, "d must divide h without remainder!\n"); return 1; } params->h = h; params->d = d; params->n = n; params->index_len = (h + 7) / 8; xmss_params xmss_par; if (xmss_set_params(&xmss_par, n, (h/d), w, k)) { return 1; } params->xmss_par = xmss_par; return 0; } /** * Computes a leaf from a WOTS public key using an L-tree. */ static void l_tree(unsigned char *leaf, unsigned char *wots_pk, const xmss_params *params, const unsigned char *pub_seed, uint32_t addr[8]) { unsigned int l = params->wots_par.len; unsigned int n = params->n; uint32_t i = 0; uint32_t height = 0; uint32_t bound; //ADRS.setTreeHeight(0); setTreeHeight(addr, height); while (l > 1) { bound = l >> 1; //floor(l / 2); for (i = 0; i < bound; i++) { //ADRS.setTreeIndex(i); setTreeIndex(addr, i); //wots_pk[i] = RAND_HASH(pk[2i], pk[2i + 1], SEED, ADRS); hash_h(wots_pk+i*n, wots_pk+i*2*n, pub_seed, addr, n); } //if ( l % 2 == 1 ) { if (l & 1) { //pk[floor(l / 2) + 1] = pk[l]; memcpy(wots_pk+(l>>1)*n, wots_pk+(l-1)*n, n); //l = ceil(l / 2); l=(l>>1)+1; } else { //l = ceil(l / 2); l=(l>>1); } //ADRS.setTreeHeight(ADRS.getTreeHeight() + 1); height++; setTreeHeight(addr, height); } //return pk[0]; memcpy(leaf, wots_pk, n); } /** * Computes the leaf at a given address. First generates the WOTS key pair, then computes leaf using l_tree. As this happens position independent, we only require that addr encodes the right ltree-address. */ static void gen_leaf_wots(unsigned char *leaf, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, uint32_t ltree_addr[8], uint32_t ots_addr[8]) { unsigned char seed[params->n]; unsigned char pk[params->wots_par.keysize]; get_seed(seed, sk_seed, params->n, ots_addr); wots_pkgen(pk, seed, &(params->wots_par), pub_seed, ots_addr); l_tree(leaf, pk, params, pub_seed, ltree_addr); } static int treehash_minheight_on_stack(bds_state* state, const xmss_params *params, const treehash_inst *treehash) { unsigned int r = params->h, i; for (i = 0; i < treehash->stackusage; i++) { if (state->stacklevels[state->stackoffset - i - 1] < r) { r = state->stacklevels[state->stackoffset - i - 1]; } } return r; } /** * Merkle's TreeHash algorithm. The address only needs to initialize the first 78 bits of addr. Everything else will be set by treehash. * Currently only used for key generation. * */ static void treehash_setup(unsigned char *node, int height, int index, bds_state *state, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const uint32_t addr[8]) { unsigned int idx = index; unsigned int n = params->n; unsigned int h = params->h; unsigned int k = params->k; // use three different addresses because at this point we use all three formats in parallel uint32_t ots_addr[8]; uint32_t ltree_addr[8]; uint32_t node_addr[8]; // only copy layer and tree address parts memcpy(ots_addr, addr, 12); // type = ots setType(ots_addr, 0); memcpy(ltree_addr, addr, 12); setType(ltree_addr, 1); memcpy(node_addr, addr, 12); setType(node_addr, 2); uint32_t lastnode, i; unsigned char stack[(height+1)*n]; unsigned int stacklevels[height+1]; unsigned int stackoffset=0; unsigned int nodeh; lastnode = idx+(1<<height); for (i = 0; i < h-k; i++) { state->treehash[i].h = i; state->treehash[i].completed = 1; state->treehash[i].stackusage = 0; } i = 0; for (; idx < lastnode; idx++) { setLtreeADRS(ltree_addr, idx); setOTSADRS(ots_addr, idx); gen_leaf_wots(stack+stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr); stacklevels[stackoffset] = 0; stackoffset++; if (h - k > 0 && i == 3) { memcpy(state->treehash[0].node, stack+stackoffset*n, n); } while (stackoffset>1 && stacklevels[stackoffset-1] == stacklevels[stackoffset-2]) { nodeh = stacklevels[stackoffset-1]; if (i >> nodeh == 1) { memcpy(state->auth + nodeh*n, stack+(stackoffset-1)*n, n); } else { if (nodeh < h - k && i >> nodeh == 3) { memcpy(state->treehash[nodeh].node, stack+(stackoffset-1)*n, n); } else if (nodeh >= h - k) { memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((i >> nodeh) - 3) >> 1)) * n, stack+(stackoffset-1)*n, n); } } setTreeHeight(node_addr, stacklevels[stackoffset-1]); setTreeIndex(node_addr, (idx >> (stacklevels[stackoffset-1]+1))); hash_h(stack+(stackoffset-2)*n, stack+(stackoffset-2)*n, pub_seed, node_addr, n); stacklevels[stackoffset-2]++; stackoffset--; } i++; } for (i = 0; i < n; i++) node[i] = stack[i]; } static void treehash_update(treehash_inst *treehash, bds_state *state, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const uint32_t addr[8]) { int n = params->n; uint32_t ots_addr[8]; uint32_t ltree_addr[8]; uint32_t node_addr[8]; // only copy layer and tree address parts memcpy(ots_addr, addr, 12); // type = ots setType(ots_addr, 0); memcpy(ltree_addr, addr, 12); setType(ltree_addr, 1); memcpy(node_addr, addr, 12); setType(node_addr, 2); setLtreeADRS(ltree_addr, treehash->next_idx); setOTSADRS(ots_addr, treehash->next_idx); unsigned char nodebuffer[2 * n]; unsigned int nodeheight = 0; gen_leaf_wots(nodebuffer, sk_seed, params, pub_seed, ltree_addr, ots_addr); while (treehash->stackusage > 0 && state->stacklevels[state->stackoffset-1] == nodeheight) { memcpy(nodebuffer + n, nodebuffer, n); memcpy(nodebuffer, state->stack + (state->stackoffset-1)*n, n); setTreeHeight(node_addr, nodeheight); setTreeIndex(node_addr, (treehash->next_idx >> (nodeheight+1))); hash_h(nodebuffer, nodebuffer, pub_seed, node_addr, n); nodeheight++; treehash->stackusage--; state->stackoffset--; } if (nodeheight == treehash->h) { // this also implies stackusage == 0 memcpy(treehash->node, nodebuffer, n); treehash->completed = 1; } else { memcpy(state->stack + state->stackoffset*n, nodebuffer, n); treehash->stackusage++; state->stacklevels[state->stackoffset] = nodeheight; state->stackoffset++; treehash->next_idx++; } } /** * Computes a root node given a leaf and an authapth */ static void validate_authpath(unsigned char *root, const unsigned char *leaf, unsigned long leafidx, const unsigned char *authpath, const xmss_params *params, const unsigned char *pub_seed, uint32_t addr[8]) { unsigned int n = params->n; uint32_t i, j; unsigned char buffer[2*n]; // If leafidx is odd (last bit = 1), current path element is a right child and authpath has to go to the left. // Otherwise, it is the other way around if (leafidx & 1) { for (j = 0; j < n; j++) buffer[n+j] = leaf[j]; for (j = 0; j < n; j++) buffer[j] = authpath[j]; } else { for (j = 0; j < n; j++) buffer[j] = leaf[j]; for (j = 0; j < n; j++) buffer[n+j] = authpath[j]; } authpath += n; for (i=0; i < params->h-1; i++) { setTreeHeight(addr, i); leafidx >>= 1; setTreeIndex(addr, leafidx); if (leafidx&1) { hash_h(buffer+n, buffer, pub_seed, addr, n); for (j = 0; j < n; j++) buffer[j] = authpath[j]; } else { hash_h(buffer, buffer, pub_seed, addr, n); for (j = 0; j < n; j++) buffer[j+n] = authpath[j]; } authpath += n; } setTreeHeight(addr, (params->h-1)); leafidx >>= 1; setTreeIndex(addr, leafidx); hash_h(root, buffer, pub_seed, addr, n); } /** * Performs one treehash update on the instance that needs it the most. * Returns 1 if such an instance was not found **/ static char bds_treehash_update(bds_state *state, unsigned int updates, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, const uint32_t addr[8]) { uint32_t i, j; unsigned int level, l_min, low; unsigned int h = params->h; unsigned int k = params->k; unsigned int used = 0; for (j = 0; j < updates; j++) { l_min = h; level = h - k; for (i = 0; i < h - k; i++) { if (state->treehash[i].completed) { low = h; } else if (state->treehash[i].stackusage == 0) { low = i; } else { low = treehash_minheight_on_stack(state, params, &(state->treehash[i])); } if (low < l_min) { level = i; l_min = low; } } if (level == h - k) { break; } treehash_update(&(state->treehash[level]), state, sk_seed, params, pub_seed, addr); used++; } return updates - used; } /** * Updates the state (typically NEXT_i) by adding a leaf and updating the stack * Returns 1 if all leaf nodes have already been processed **/ static char bds_state_update(bds_state *state, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, const uint32_t addr[8]) { uint32_t ltree_addr[8]; uint32_t node_addr[8]; uint32_t ots_addr[8]; int n = params->n; int h = params->h; int k = params->k; int nodeh; int idx = state->next_leaf; if (idx == 1 << h) { return 1; } // only copy layer and tree address parts memcpy(ots_addr, addr, 12); // type = ots setType(ots_addr, 0); memcpy(ltree_addr, addr, 12); setType(ltree_addr, 1); memcpy(node_addr, addr, 12); setType(node_addr, 2); setOTSADRS(ots_addr, idx); setLtreeADRS(ltree_addr, idx); gen_leaf_wots(state->stack+state->stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr); state->stacklevels[state->stackoffset] = 0; state->stackoffset++; if (h - k > 0 && idx == 3) { memcpy(state->treehash[0].node, state->stack+state->stackoffset*n, n); } while (state->stackoffset>1 && state->stacklevels[state->stackoffset-1] == state->stacklevels[state->stackoffset-2]) { nodeh = state->stacklevels[state->stackoffset-1]; if (idx >> nodeh == 1) { memcpy(state->auth + nodeh*n, state->stack+(state->stackoffset-1)*n, n); } else { if (nodeh < h - k && idx >> nodeh == 3) { memcpy(state->treehash[nodeh].node, state->stack+(state->stackoffset-1)*n, n); } else if (nodeh >= h - k) { memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((idx >> nodeh) - 3) >> 1)) * n, state->stack+(state->stackoffset-1)*n, n); } } setTreeHeight(node_addr, state->stacklevels[state->stackoffset-1]); setTreeIndex(node_addr, (idx >> (state->stacklevels[state->stackoffset-1]+1))); hash_h(state->stack+(state->stackoffset-2)*n, state->stack+(state->stackoffset-2)*n, pub_seed, node_addr, n); state->stacklevels[state->stackoffset-2]++; state->stackoffset--; } state->next_leaf++; return 0; } /** * Returns the auth path for node leaf_idx and computes the auth path for the * next leaf node, using the algorithm described by Buchmann, Dahmen and Szydlo * in "Post Quantum Cryptography", Springer 2009. */ static void bds_round(bds_state *state, const unsigned long leaf_idx, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, uint32_t addr[8]) { unsigned int i; unsigned int n = params->n; unsigned int h = params->h; unsigned int k = params->k; unsigned int tau = h; unsigned int startidx; unsigned int offset, rowidx; unsigned char buf[2 * n]; uint32_t ots_addr[8]; uint32_t ltree_addr[8]; uint32_t node_addr[8]; // only copy layer and tree address parts memcpy(ots_addr, addr, 12); // type = ots setType(ots_addr, 0); memcpy(ltree_addr, addr, 12); setType(ltree_addr, 1); memcpy(node_addr, addr, 12); setType(node_addr, 2); for (i = 0; i < h; i++) { if (! ((leaf_idx >> i) & 1)) { tau = i; break; } } if (tau > 0) { memcpy(buf, state->auth + (tau-1) * n, n); // we need to do this before refreshing state->keep to prevent overwriting memcpy(buf + n, state->keep + ((tau-1) >> 1) * n, n); } if (!((leaf_idx >> (tau + 1)) & 1) && (tau < h - 1)) { memcpy(state->keep + (tau >> 1)*n, state->auth + tau*n, n); } if (tau == 0) { setLtreeADRS(ltree_addr, leaf_idx); setOTSADRS(ots_addr, leaf_idx); gen_leaf_wots(state->auth, sk_seed, params, pub_seed, ltree_addr, ots_addr); } else { setTreeHeight(node_addr, (tau-1)); setTreeIndex(node_addr, leaf_idx >> tau); hash_h(state->auth + tau * n, buf, pub_seed, node_addr, n); for (i = 0; i < tau; i++) { if (i < h - k) { memcpy(state->auth + i * n, state->treehash[i].node, n); } else { offset = (1 << (h - 1 - i)) + i - h; rowidx = ((leaf_idx >> i) - 1) >> 1; memcpy(state->auth + i * n, state->retain + (offset + rowidx) * n, n); } } for (i = 0; i < ((tau < h - k) ? tau : (h - k)); i++) { startidx = leaf_idx + 1 + 3 * (1 << i); if (startidx < 1U << h) { state->treehash[i].h = i; state->treehash[i].next_idx = startidx; state->treehash[i].completed = 0; state->treehash[i].stackusage = 0; } } } } /* * Generates a XMSS key pair for a given parameter set. * Format sk: [(32bit) idx || SK_SEED || SK_PRF || PUB_SEED || root] * Format pk: [root || PUB_SEED] omitting algo oid. */ int xmss_keypair(unsigned char *pk, unsigned char *sk, bds_state *state, xmss_params *params) { unsigned int n = params->n; // Set idx = 0 sk[0] = 0; sk[1] = 0; sk[2] = 0; sk[3] = 0; // Init SK_SEED (n byte), SK_PRF (n byte), and PUB_SEED (n byte) randombytes(sk+4, 3*n); // Copy PUB_SEED to public key memcpy(pk+n, sk+4+2*n, n); uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; // Compute root treehash_setup(pk, params->h, 0, state, sk+4, params, sk+4+2*n, addr); // copy root to sk memcpy(sk+4+3*n, pk, n); return 0; } /** * Signs a message. * Returns * 1. an array containing the signature followed by the message AND * 2. an updated secret key! * */ int xmss_sign(unsigned char *sk, bds_state *state, unsigned char *sig_msg, unsigned long long *sig_msg_len, const unsigned char *msg, unsigned long long msglen, const xmss_params *params) { unsigned int h = params->h; unsigned int n = params->n; unsigned int k = params->k; uint16_t i = 0; // Extract SK unsigned long idx = ((unsigned long)sk[0] << 24) | ((unsigned long)sk[1] << 16) | ((unsigned long)sk[2] << 8) | sk[3]; unsigned char sk_seed[n]; memcpy(sk_seed, sk+4, n); unsigned char sk_prf[n]; memcpy(sk_prf, sk+4+n, n); unsigned char pub_seed[n]; memcpy(pub_seed, sk+4+2*n, n); // index as 32 bytes string unsigned char idx_bytes_32[32]; to_byte(idx_bytes_32, idx, 32); unsigned char hash_key[3*n]; // Update SK sk[0] = ((idx + 1) >> 24) & 255; sk[1] = ((idx + 1) >> 16) & 255; sk[2] = ((idx + 1) >> 8) & 255; sk[3] = (idx + 1) & 255; // -- Secret key for this non-forward-secure version is now updated. // -- A productive implementation should use a file handle instead and write the updated secret key at this point! // Init working params unsigned char R[n]; unsigned char msg_h[n]; unsigned char ots_seed[n]; uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; // --------------------------------- // Message Hashing // --------------------------------- // Message Hash: // First compute pseudorandom value prf(R, idx_bytes_32, sk_prf, n); // Generate hash key (R || root || idx) memcpy(hash_key, R, n); memcpy(hash_key+n, sk+4+3*n, n); to_byte(hash_key+2*n, idx, n); // Then use it for message digest h_msg(msg_h, msg, msglen, hash_key, 3*n, n); // Start collecting signature *sig_msg_len = 0; // Copy index to signature sig_msg[0] = (idx >> 24) & 255; sig_msg[1] = (idx >> 16) & 255; sig_msg[2] = (idx >> 8) & 255; sig_msg[3] = idx & 255; sig_msg += 4; *sig_msg_len += 4; // Copy R to signature for (i = 0; i < n; i++) sig_msg[i] = R[i]; sig_msg += n; *sig_msg_len += n; // ---------------------------------- // Now we start to "really sign" // ---------------------------------- // Prepare Address setType(ots_addr, 0); setOTSADRS(ots_addr, idx); // Compute seed for OTS key pair get_seed(ots_seed, sk_seed, n, ots_addr); // Compute WOTS signature wots_sign(sig_msg, msg_h, ots_seed, &(params->wots_par), pub_seed, ots_addr); sig_msg += params->wots_par.keysize; *sig_msg_len += params->wots_par.keysize; // the auth path was already computed during the previous round memcpy(sig_msg, state->auth, h*n); if (idx < (1U << h) - 1) { bds_round(state, idx, sk_seed, params, pub_seed, ots_addr); bds_treehash_update(state, (h - k) >> 1, sk_seed, params, pub_seed, ots_addr); } /* TODO: save key/bds state here! */ sig_msg += params->h*n; *sig_msg_len += params->h*n; //Whipe secret elements? //zerobytes(tsk, CRYPTO_SECRETKEYBYTES); memcpy(sig_msg, msg, msglen); *sig_msg_len += msglen; return 0; } /** * Verifies a given message signature pair under a given public key. */ int xmss_sign_open(unsigned char *msg, unsigned long long *msglen, const unsigned char *sig_msg, unsigned long long sig_msg_len, const unsigned char *pk, const xmss_params *params) { unsigned int n = params->n; unsigned long long i, m_len; unsigned long idx=0; unsigned char wots_pk[params->wots_par.keysize]; unsigned char pkhash[n]; unsigned char root[n]; unsigned char msg_h[n]; unsigned char hash_key[3*n]; unsigned char pub_seed[n]; memcpy(pub_seed, pk+n, n); // Init addresses uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; uint32_t ltree_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; uint32_t node_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; setType(ots_addr, 0); setType(ltree_addr, 1); setType(node_addr, 2); // Extract index idx = ((unsigned long)sig_msg[0] << 24) | ((unsigned long)sig_msg[1] << 16) | ((unsigned long)sig_msg[2] << 8) | sig_msg[3]; printf("verify:: idx = %lu\n", idx); // Generate hash key (R || root || idx) memcpy(hash_key, sig_msg+4,n); memcpy(hash_key+n, pk, n); to_byte(hash_key+2*n, idx, n); sig_msg += (n+4); sig_msg_len -= (n+4); // hash message unsigned long long tmp_sig_len = params->wots_par.keysize+params->h*n; m_len = sig_msg_len - tmp_sig_len; h_msg(msg_h, sig_msg + tmp_sig_len, m_len, hash_key, 3*n, n); //----------------------- // Verify signature //----------------------- // Prepare Address setOTSADRS(ots_addr, idx); // Check WOTS signature wots_pkFromSig(wots_pk, sig_msg, msg_h, &(params->wots_par), pub_seed, ots_addr); sig_msg += params->wots_par.keysize; sig_msg_len -= params->wots_par.keysize; // Compute Ltree setLtreeADRS(ltree_addr, idx); l_tree(pkhash, wots_pk, params, pub_seed, ltree_addr); // Compute root validate_authpath(root, pkhash, idx, sig_msg, params, pub_seed, node_addr); sig_msg += params->h*n; sig_msg_len -= params->h*n; for (i = 0; i < n; i++) if (root[i] != pk[i]) goto fail; *msglen = sig_msg_len; for (i = 0; i < *msglen; i++) msg[i] = sig_msg[i]; return 0; fail: *msglen = sig_msg_len; for (i = 0; i < *msglen; i++) msg[i] = 0; *msglen = -1; return -1; } /* * Generates a XMSSMT key pair for a given parameter set. * Format sk: [(ceil(h/8) bit) idx || SK_SEED || SK_PRF || PUB_SEED || root] * Format pk: [root || PUB_SEED] omitting algo oid. */ int xmssmt_keypair(unsigned char *pk, unsigned char *sk, bds_state *states, unsigned char *wots_sigs, xmssmt_params *params) { unsigned int n = params->n; unsigned int i; unsigned char ots_seed[params->n]; // Set idx = 0 for (i = 0; i < params->index_len; i++) { sk[i] = 0; } // Init SK_SEED (n byte), SK_PRF (n byte), and PUB_SEED (n byte) randombytes(sk+params->index_len, 3*n); // Copy PUB_SEED to public key memcpy(pk+n, sk+params->index_len+2*n, n); // Set address to point on the single tree on layer d-1 uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; setLayerADRS(addr, (params->d-1)); // Set up state and compute wots signatures for all but topmost tree root for (i = 0; i < params->d - 1; i++) { // Compute seed for OTS key pair treehash_setup(pk, params->xmss_par.h, 0, states + i, sk+params->index_len, &(params->xmss_par), pk+n, addr); setLayerADRS(addr, (i+1)); get_seed(ots_seed, sk+params->index_len, n, addr); wots_sign(wots_sigs + i*params->xmss_par.wots_par.keysize, pk, ots_seed, &(params->xmss_par.wots_par), pk+n, addr); } treehash_setup(pk, params->xmss_par.h, 0, states + i, sk+params->index_len, &(params->xmss_par), pk+n, addr); memcpy(sk+params->index_len+3*n, pk, n); return 0; } /** * Signs a message. * Returns * 1. an array containing the signature followed by the message AND * 2. an updated secret key! * */ int xmssmt_sign(unsigned char *sk, bds_state *states, unsigned char *wots_sigs, unsigned char *sig_msg, unsigned long long *sig_msg_len, const unsigned char *msg, unsigned long long msglen, const xmssmt_params *params) { unsigned int n = params->n; unsigned int tree_h = params->xmss_par.h; unsigned int h = params->h; unsigned int k = params->xmss_par.k; unsigned int idx_len = params->index_len; uint64_t idx_tree; uint32_t idx_leaf; uint64_t i, j; int needswap_upto = -1; unsigned int updates; unsigned char sk_seed[n]; unsigned char sk_prf[n]; unsigned char pub_seed[n]; // Init working params unsigned char R[n]; unsigned char msg_h[n]; unsigned char hash_key[3*n]; unsigned char ots_seed[n]; uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; unsigned char idx_bytes_32[32]; bds_state tmp; // Extract SK unsigned long long idx = 0; for (i = 0; i < idx_len; i++) { idx |= ((unsigned long long)sk[i]) << 8*(idx_len - 1 - i); } memcpy(sk_seed, sk+idx_len, n); memcpy(sk_prf, sk+idx_len+n, n); memcpy(pub_seed, sk+idx_len+2*n, n); // Update SK for (i = 0; i < idx_len; i++) { sk[i] = ((idx + 1) >> 8*(idx_len - 1 - i)) & 255; } // -- Secret key for this non-forward-secure version is now updated. // -- A productive implementation should use a file handle instead and write the updated secret key at this point! // --------------------------------- // Message Hashing // --------------------------------- // Message Hash: // First compute pseudorandom value to_byte(idx_bytes_32, idx, 32); prf(R, idx_bytes_32, sk_prf, n); // Generate hash key (R || root || idx) memcpy(hash_key, R, n); memcpy(hash_key+n, sk+idx_len+3*n, n); to_byte(hash_key+2*n, idx, n); // Then use it for message digest h_msg(msg_h, msg, msglen, hash_key, 3*n, n); // Start collecting signature *sig_msg_len = 0; // Copy index to signature for (i = 0; i < idx_len; i++) { sig_msg[i] = (idx >> 8*(idx_len - 1 - i)) & 255; } sig_msg += idx_len; *sig_msg_len += idx_len; // Copy R to signature for (i = 0; i < n; i++) sig_msg[i] = R[i]; sig_msg += n; *sig_msg_len += n; // ---------------------------------- // Now we start to "really sign" // ---------------------------------- // Handle lowest layer separately as it is slightly different... // Prepare Address setType(ots_addr, 0); idx_tree = idx >> tree_h; idx_leaf = (idx & ((1 << tree_h)-1)); setLayerADRS(ots_addr, 0); setTreeADRS(ots_addr, idx_tree); setOTSADRS(ots_addr, idx_leaf); // Compute seed for OTS key pair get_seed(ots_seed, sk_seed, n, ots_addr); // Compute WOTS signature wots_sign(sig_msg, msg_h, ots_seed, &(params->xmss_par.wots_par), pub_seed, ots_addr); sig_msg += params->xmss_par.wots_par.keysize; *sig_msg_len += params->xmss_par.wots_par.keysize; memcpy(sig_msg, states[0].auth, tree_h*n); sig_msg += tree_h*n; *sig_msg_len += tree_h*n; // prepare signature of remaining layers for (i = 1; i < params->d; i++) { // put WOTS signature in place memcpy(sig_msg, wots_sigs + (i-1)*params->xmss_par.wots_par.keysize, params->xmss_par.wots_par.keysize); sig_msg += params->xmss_par.wots_par.keysize; *sig_msg_len += params->xmss_par.wots_par.keysize; // put AUTH nodes in place memcpy(sig_msg, states[i].auth, tree_h*n); sig_msg += tree_h*n; *sig_msg_len += tree_h*n; } updates = (tree_h - k) >> 1; setTreeADRS(addr, (idx_tree + 1)); // mandatory update for NEXT_0 (does not count towards h-k/2) if NEXT_0 exists if ((1 + idx_tree) * (1 << tree_h) + idx_leaf < (1ULL << h)) { bds_state_update(&states[params->d], sk_seed, &(params->xmss_par), pub_seed, addr); } for (i = 0; i < params->d; i++) { // check if we're not at the end of a tree if (! (((idx + 1) & ((1ULL << ((i+1)*tree_h)) - 1)) == 0)) { idx_leaf = (idx >> (tree_h * i)) & ((1 << tree_h)-1); idx_tree = (idx >> (tree_h * (i+1))); setLayerADRS(addr, i); setTreeADRS(addr, idx_tree); if (i == (unsigned int) (needswap_upto + 1)) { bds_round(&states[i], idx_leaf, sk_seed, &(params->xmss_par), pub_seed, addr); } updates = bds_treehash_update(&states[i], updates, sk_seed, &(params->xmss_par), pub_seed, addr); setTreeADRS(addr, (idx_tree + 1)); // if a NEXT-tree exists for this level; if ((1 + idx_tree) * (1 << tree_h) + idx_leaf < (1ULL << (h - tree_h * i))) { if (i > 0 && updates > 0 && states[params->d + i].next_leaf < (1ULL << h)) { bds_state_update(&states[params->d + i], sk_seed, &(params->xmss_par), pub_seed, addr); updates--; } } } else if (idx < (1ULL << h) - 1) { memcpy(&tmp, states+params->d + i, sizeof(bds_state)); memcpy(states+params->d + i, states + i, sizeof(bds_state)); memcpy(states + i, &tmp, sizeof(bds_state)); setLayerADRS(ots_addr, (i+1)); setTreeADRS(ots_addr, ((idx + 1) >> ((i+2) * tree_h))); setOTSADRS(ots_addr, (((idx >> ((i+1) * tree_h)) + 1) & ((1 << tree_h)-1))); get_seed(ots_seed, sk+params->index_len, n, ots_addr); wots_sign(wots_sigs + i*params->xmss_par.wots_par.keysize, states[i].stack, ots_seed, &(params->xmss_par.wots_par), pub_seed, ots_addr); states[params->d + i].stackoffset = 0; states[params->d + i].next_leaf = 0; updates--; // WOTS-signing counts as one update needswap_upto = i; for (j = 0; j < tree_h-k; j++) { states[i].treehash[j].completed = 1; } } } //Whipe secret elements? //zerobytes(tsk, CRYPTO_SECRETKEYBYTES); memcpy(sig_msg, msg, msglen); *sig_msg_len += msglen; return 0; } /** * Verifies a given message signature pair under a given public key. */ int xmssmt_sign_open(unsigned char *msg, unsigned long long *msglen, const unsigned char *sig_msg, unsigned long long sig_msg_len, const unsigned char *pk, const xmssmt_params *params) { unsigned int n = params->n; unsigned int tree_h = params->xmss_par.h; unsigned int idx_len = params->index_len; uint64_t idx_tree; uint32_t idx_leaf; unsigned long long i, m_len; unsigned long long idx=0; unsigned char wots_pk[params->xmss_par.wots_par.keysize]; unsigned char pkhash[n]; unsigned char root[n]; unsigned char msg_h[n]; unsigned char hash_key[3*n]; unsigned char pub_seed[n]; memcpy(pub_seed, pk+n, n); // Init addresses uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; uint32_t ltree_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; uint32_t node_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0}; // Extract index for (i = 0; i < idx_len; i++) { idx |= ((unsigned long long)sig_msg[i]) << (8*(idx_len - 1 - i)); } printf("verify:: idx = %llu\n", idx); sig_msg += idx_len; sig_msg_len -= idx_len; // Generate hash key (R || root || idx) memcpy(hash_key, sig_msg,n); memcpy(hash_key+n, pk, n); to_byte(hash_key+2*n, idx, n); sig_msg += n; sig_msg_len -= n; // hash message (recall, R is now on pole position at sig_msg unsigned long long tmp_sig_len = (params->d * params->xmss_par.wots_par.keysize) + (params->h * n); m_len = sig_msg_len - tmp_sig_len; h_msg(msg_h, sig_msg + tmp_sig_len, m_len, hash_key, 3*n, n); //----------------------- // Verify signature //----------------------- // Prepare Address idx_tree = idx >> tree_h; idx_leaf = (idx & ((1 << tree_h)-1)); setLayerADRS(ots_addr, 0); setTreeADRS(ots_addr, idx_tree); setType(ots_addr, 0); memcpy(ltree_addr, ots_addr, 12); setType(ltree_addr, 1); memcpy(node_addr, ltree_addr, 12); setType(node_addr, 2); setOTSADRS(ots_addr, idx_leaf); // Check WOTS signature wots_pkFromSig(wots_pk, sig_msg, msg_h, &(params->xmss_par.wots_par), pub_seed, ots_addr); sig_msg += params->xmss_par.wots_par.keysize; sig_msg_len -= params->xmss_par.wots_par.keysize; // Compute Ltree setLtreeADRS(ltree_addr, idx_leaf); l_tree(pkhash, wots_pk, &(params->xmss_par), pub_seed, ltree_addr); // Compute root validate_authpath(root, pkhash, idx_leaf, sig_msg, &(params->xmss_par), pub_seed, node_addr); sig_msg += tree_h*n; sig_msg_len -= tree_h*n; for (i = 1; i < params->d; i++) { // Prepare Address idx_leaf = (idx_tree & ((1 << tree_h)-1)); idx_tree = idx_tree >> tree_h; setLayerADRS(ots_addr, i); setTreeADRS(ots_addr, idx_tree); setType(ots_addr, 0); memcpy(ltree_addr, ots_addr, 12); setType(ltree_addr, 1); memcpy(node_addr, ltree_addr, 12); setType(node_addr, 2); setOTSADRS(ots_addr, idx_leaf); // Check WOTS signature wots_pkFromSig(wots_pk, sig_msg, root, &(params->xmss_par.wots_par), pub_seed, ots_addr); sig_msg += params->xmss_par.wots_par.keysize; sig_msg_len -= params->xmss_par.wots_par.keysize; // Compute Ltree setLtreeADRS(ltree_addr, idx_leaf); l_tree(pkhash, wots_pk, &(params->xmss_par), pub_seed, ltree_addr); // Compute root validate_authpath(root, pkhash, idx_leaf, sig_msg, &(params->xmss_par), pub_seed, node_addr); sig_msg += tree_h*n; sig_msg_len -= tree_h*n; } for (i = 0; i < n; i++) if (root[i] != pk[i]) goto fail; *msglen = sig_msg_len; for (i = 0; i < *msglen; i++) msg[i] = sig_msg[i]; return 0; fail: *msglen = sig_msg_len; for (i = 0; i < *msglen; i++) msg[i] = 0; *msglen = -1; return -1; } #endif /* WITH_XMSS */