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markus@openbsd.orgcb1f9442018-03-22 07:06:11 +00001/* $OpenBSD: xmss_fast.c,v 1.3 2018/03/22 07:06:11 markus Exp $ */
markus@openbsd.org1b11ea72018-02-23 15:58:37 +00002/*
3xmss_fast.c version 20160722
4Andreas Hülsing
5Joost Rijneveld
6Public domain.
7*/
8
Damien Millerf8854742018-02-26 12:18:14 +11009#include "includes.h"
Darren Tucker941e0d32018-02-28 19:59:35 +110010#ifdef WITH_XMSS
Damien Millerf8854742018-02-26 12:18:14 +110011
markus@openbsd.org1b11ea72018-02-23 15:58:37 +000012#include <stdlib.h>
13#include <string.h>
Darren Tuckerc7ef4a32018-02-26 17:42:56 +110014#ifdef HAVE_STDINT_H
markus@openbsd.org1b11ea72018-02-23 15:58:37 +000015#include <stdint.h>
Darren Tuckerc7ef4a32018-02-26 17:42:56 +110016#endif
markus@openbsd.org1b11ea72018-02-23 15:58:37 +000017
markus@openbsd.orgcb1f9442018-03-22 07:06:11 +000018#include "xmss_fast.h"
markus@openbsd.org1b11ea72018-02-23 15:58:37 +000019#include "crypto_api.h"
20#include "xmss_wots.h"
21#include "xmss_hash.h"
22
23#include "xmss_commons.h"
24#include "xmss_hash_address.h"
25// For testing
26#include "stdio.h"
27
28
29
30/**
31 * Used for pseudorandom keygeneration,
32 * generates the seed for the WOTS keypair at address addr
33 *
34 * takes n byte sk_seed and returns n byte seed using 32 byte address addr.
35 */
36static void get_seed(unsigned char *seed, const unsigned char *sk_seed, int n, uint32_t addr[8])
37{
38 unsigned char bytes[32];
39 // Make sure that chain addr, hash addr, and key bit are 0!
40 setChainADRS(addr,0);
41 setHashADRS(addr,0);
42 setKeyAndMask(addr,0);
43 // Generate pseudorandom value
44 addr_to_byte(bytes, addr);
45 prf(seed, bytes, sk_seed, n);
46}
47
48/**
49 * Initialize xmss params struct
50 * parameter names are the same as in the draft
51 * parameter k is K as used in the BDS algorithm
52 */
53int xmss_set_params(xmss_params *params, int n, int h, int w, int k)
54{
55 if (k >= h || k < 2 || (h - k) % 2) {
56 fprintf(stderr, "For BDS traversal, H - K must be even, with H > K >= 2!\n");
57 return 1;
58 }
59 params->h = h;
60 params->n = n;
61 params->k = k;
62 wots_params wots_par;
63 wots_set_params(&wots_par, n, w);
64 params->wots_par = wots_par;
65 return 0;
66}
67
68/**
69 * Initialize BDS state struct
70 * parameter names are the same as used in the description of the BDS traversal
71 */
72void 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)
73{
74 state->stack = stack;
75 state->stackoffset = stackoffset;
76 state->stacklevels = stacklevels;
77 state->auth = auth;
78 state->keep = keep;
79 state->treehash = treehash;
80 state->retain = retain;
81 state->next_leaf = next_leaf;
82}
83
84/**
85 * Initialize xmssmt_params struct
86 * parameter names are the same as in the draft
87 *
88 * Especially h is the total tree height, i.e. the XMSS trees have height h/d
89 */
90int xmssmt_set_params(xmssmt_params *params, int n, int h, int d, int w, int k)
91{
92 if (h % d) {
93 fprintf(stderr, "d must divide h without remainder!\n");
94 return 1;
95 }
96 params->h = h;
97 params->d = d;
98 params->n = n;
99 params->index_len = (h + 7) / 8;
100 xmss_params xmss_par;
101 if (xmss_set_params(&xmss_par, n, (h/d), w, k)) {
102 return 1;
103 }
104 params->xmss_par = xmss_par;
105 return 0;
106}
107
108/**
109 * Computes a leaf from a WOTS public key using an L-tree.
110 */
111static void l_tree(unsigned char *leaf, unsigned char *wots_pk, const xmss_params *params, const unsigned char *pub_seed, uint32_t addr[8])
112{
113 unsigned int l = params->wots_par.len;
114 unsigned int n = params->n;
115 uint32_t i = 0;
116 uint32_t height = 0;
117 uint32_t bound;
118
119 //ADRS.setTreeHeight(0);
120 setTreeHeight(addr, height);
121
122 while (l > 1) {
123 bound = l >> 1; //floor(l / 2);
124 for (i = 0; i < bound; i++) {
125 //ADRS.setTreeIndex(i);
126 setTreeIndex(addr, i);
127 //wots_pk[i] = RAND_HASH(pk[2i], pk[2i + 1], SEED, ADRS);
128 hash_h(wots_pk+i*n, wots_pk+i*2*n, pub_seed, addr, n);
129 }
130 //if ( l % 2 == 1 ) {
131 if (l & 1) {
132 //pk[floor(l / 2) + 1] = pk[l];
133 memcpy(wots_pk+(l>>1)*n, wots_pk+(l-1)*n, n);
134 //l = ceil(l / 2);
135 l=(l>>1)+1;
136 }
137 else {
138 //l = ceil(l / 2);
139 l=(l>>1);
140 }
141 //ADRS.setTreeHeight(ADRS.getTreeHeight() + 1);
142 height++;
143 setTreeHeight(addr, height);
144 }
145 //return pk[0];
146 memcpy(leaf, wots_pk, n);
147}
148
149/**
150 * 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.
151 */
152static 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])
153{
154 unsigned char seed[params->n];
155 unsigned char pk[params->wots_par.keysize];
156
157 get_seed(seed, sk_seed, params->n, ots_addr);
158 wots_pkgen(pk, seed, &(params->wots_par), pub_seed, ots_addr);
159
160 l_tree(leaf, pk, params, pub_seed, ltree_addr);
161}
162
163static int treehash_minheight_on_stack(bds_state* state, const xmss_params *params, const treehash_inst *treehash) {
164 unsigned int r = params->h, i;
165 for (i = 0; i < treehash->stackusage; i++) {
166 if (state->stacklevels[state->stackoffset - i - 1] < r) {
167 r = state->stacklevels[state->stackoffset - i - 1];
168 }
169 }
170 return r;
171}
172
173/**
174 * Merkle's TreeHash algorithm. The address only needs to initialize the first 78 bits of addr. Everything else will be set by treehash.
175 * Currently only used for key generation.
176 *
177 */
178static 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])
179{
180 unsigned int idx = index;
181 unsigned int n = params->n;
182 unsigned int h = params->h;
183 unsigned int k = params->k;
184 // use three different addresses because at this point we use all three formats in parallel
185 uint32_t ots_addr[8];
186 uint32_t ltree_addr[8];
187 uint32_t node_addr[8];
188 // only copy layer and tree address parts
189 memcpy(ots_addr, addr, 12);
190 // type = ots
191 setType(ots_addr, 0);
192 memcpy(ltree_addr, addr, 12);
193 setType(ltree_addr, 1);
194 memcpy(node_addr, addr, 12);
195 setType(node_addr, 2);
196
197 uint32_t lastnode, i;
198 unsigned char stack[(height+1)*n];
199 unsigned int stacklevels[height+1];
200 unsigned int stackoffset=0;
201 unsigned int nodeh;
202
203 lastnode = idx+(1<<height);
204
205 for (i = 0; i < h-k; i++) {
206 state->treehash[i].h = i;
207 state->treehash[i].completed = 1;
208 state->treehash[i].stackusage = 0;
209 }
210
211 i = 0;
212 for (; idx < lastnode; idx++) {
213 setLtreeADRS(ltree_addr, idx);
214 setOTSADRS(ots_addr, idx);
215 gen_leaf_wots(stack+stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr);
216 stacklevels[stackoffset] = 0;
217 stackoffset++;
218 if (h - k > 0 && i == 3) {
219 memcpy(state->treehash[0].node, stack+stackoffset*n, n);
220 }
221 while (stackoffset>1 && stacklevels[stackoffset-1] == stacklevels[stackoffset-2])
222 {
223 nodeh = stacklevels[stackoffset-1];
224 if (i >> nodeh == 1) {
225 memcpy(state->auth + nodeh*n, stack+(stackoffset-1)*n, n);
226 }
227 else {
228 if (nodeh < h - k && i >> nodeh == 3) {
229 memcpy(state->treehash[nodeh].node, stack+(stackoffset-1)*n, n);
230 }
231 else if (nodeh >= h - k) {
232 memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((i >> nodeh) - 3) >> 1)) * n, stack+(stackoffset-1)*n, n);
233 }
234 }
235 setTreeHeight(node_addr, stacklevels[stackoffset-1]);
236 setTreeIndex(node_addr, (idx >> (stacklevels[stackoffset-1]+1)));
237 hash_h(stack+(stackoffset-2)*n, stack+(stackoffset-2)*n, pub_seed,
238 node_addr, n);
239 stacklevels[stackoffset-2]++;
240 stackoffset--;
241 }
242 i++;
243 }
244
245 for (i = 0; i < n; i++)
246 node[i] = stack[i];
247}
248
249static 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]) {
250 int n = params->n;
251
252 uint32_t ots_addr[8];
253 uint32_t ltree_addr[8];
254 uint32_t node_addr[8];
255 // only copy layer and tree address parts
256 memcpy(ots_addr, addr, 12);
257 // type = ots
258 setType(ots_addr, 0);
259 memcpy(ltree_addr, addr, 12);
260 setType(ltree_addr, 1);
261 memcpy(node_addr, addr, 12);
262 setType(node_addr, 2);
263
264 setLtreeADRS(ltree_addr, treehash->next_idx);
265 setOTSADRS(ots_addr, treehash->next_idx);
266
267 unsigned char nodebuffer[2 * n];
268 unsigned int nodeheight = 0;
269 gen_leaf_wots(nodebuffer, sk_seed, params, pub_seed, ltree_addr, ots_addr);
270 while (treehash->stackusage > 0 && state->stacklevels[state->stackoffset-1] == nodeheight) {
271 memcpy(nodebuffer + n, nodebuffer, n);
272 memcpy(nodebuffer, state->stack + (state->stackoffset-1)*n, n);
273 setTreeHeight(node_addr, nodeheight);
274 setTreeIndex(node_addr, (treehash->next_idx >> (nodeheight+1)));
275 hash_h(nodebuffer, nodebuffer, pub_seed, node_addr, n);
276 nodeheight++;
277 treehash->stackusage--;
278 state->stackoffset--;
279 }
280 if (nodeheight == treehash->h) { // this also implies stackusage == 0
281 memcpy(treehash->node, nodebuffer, n);
282 treehash->completed = 1;
283 }
284 else {
285 memcpy(state->stack + state->stackoffset*n, nodebuffer, n);
286 treehash->stackusage++;
287 state->stacklevels[state->stackoffset] = nodeheight;
288 state->stackoffset++;
289 treehash->next_idx++;
290 }
291}
292
293/**
294 * Computes a root node given a leaf and an authapth
295 */
296static 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])
297{
298 unsigned int n = params->n;
299
300 uint32_t i, j;
301 unsigned char buffer[2*n];
302
303 // If leafidx is odd (last bit = 1), current path element is a right child and authpath has to go to the left.
304 // Otherwise, it is the other way around
305 if (leafidx & 1) {
306 for (j = 0; j < n; j++)
307 buffer[n+j] = leaf[j];
308 for (j = 0; j < n; j++)
309 buffer[j] = authpath[j];
310 }
311 else {
312 for (j = 0; j < n; j++)
313 buffer[j] = leaf[j];
314 for (j = 0; j < n; j++)
315 buffer[n+j] = authpath[j];
316 }
317 authpath += n;
318
319 for (i=0; i < params->h-1; i++) {
320 setTreeHeight(addr, i);
321 leafidx >>= 1;
322 setTreeIndex(addr, leafidx);
323 if (leafidx&1) {
324 hash_h(buffer+n, buffer, pub_seed, addr, n);
325 for (j = 0; j < n; j++)
326 buffer[j] = authpath[j];
327 }
328 else {
329 hash_h(buffer, buffer, pub_seed, addr, n);
330 for (j = 0; j < n; j++)
331 buffer[j+n] = authpath[j];
332 }
333 authpath += n;
334 }
335 setTreeHeight(addr, (params->h-1));
336 leafidx >>= 1;
337 setTreeIndex(addr, leafidx);
338 hash_h(root, buffer, pub_seed, addr, n);
339}
340
341/**
342 * Performs one treehash update on the instance that needs it the most.
343 * Returns 1 if such an instance was not found
344 **/
345static 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]) {
346 uint32_t i, j;
347 unsigned int level, l_min, low;
348 unsigned int h = params->h;
349 unsigned int k = params->k;
350 unsigned int used = 0;
351
352 for (j = 0; j < updates; j++) {
353 l_min = h;
354 level = h - k;
355 for (i = 0; i < h - k; i++) {
356 if (state->treehash[i].completed) {
357 low = h;
358 }
359 else if (state->treehash[i].stackusage == 0) {
360 low = i;
361 }
362 else {
363 low = treehash_minheight_on_stack(state, params, &(state->treehash[i]));
364 }
365 if (low < l_min) {
366 level = i;
367 l_min = low;
368 }
369 }
370 if (level == h - k) {
371 break;
372 }
373 treehash_update(&(state->treehash[level]), state, sk_seed, params, pub_seed, addr);
374 used++;
375 }
376 return updates - used;
377}
378
379/**
380 * Updates the state (typically NEXT_i) by adding a leaf and updating the stack
381 * Returns 1 if all leaf nodes have already been processed
382 **/
383static 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]) {
384 uint32_t ltree_addr[8];
385 uint32_t node_addr[8];
386 uint32_t ots_addr[8];
387
388 int n = params->n;
389 int h = params->h;
390 int k = params->k;
391
392 int nodeh;
393 int idx = state->next_leaf;
394 if (idx == 1 << h) {
395 return 1;
396 }
397
398 // only copy layer and tree address parts
399 memcpy(ots_addr, addr, 12);
400 // type = ots
401 setType(ots_addr, 0);
402 memcpy(ltree_addr, addr, 12);
403 setType(ltree_addr, 1);
404 memcpy(node_addr, addr, 12);
405 setType(node_addr, 2);
406
407 setOTSADRS(ots_addr, idx);
408 setLtreeADRS(ltree_addr, idx);
409
410 gen_leaf_wots(state->stack+state->stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr);
411
412 state->stacklevels[state->stackoffset] = 0;
413 state->stackoffset++;
414 if (h - k > 0 && idx == 3) {
415 memcpy(state->treehash[0].node, state->stack+state->stackoffset*n, n);
416 }
417 while (state->stackoffset>1 && state->stacklevels[state->stackoffset-1] == state->stacklevels[state->stackoffset-2]) {
418 nodeh = state->stacklevels[state->stackoffset-1];
419 if (idx >> nodeh == 1) {
420 memcpy(state->auth + nodeh*n, state->stack+(state->stackoffset-1)*n, n);
421 }
422 else {
423 if (nodeh < h - k && idx >> nodeh == 3) {
424 memcpy(state->treehash[nodeh].node, state->stack+(state->stackoffset-1)*n, n);
425 }
426 else if (nodeh >= h - k) {
427 memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((idx >> nodeh) - 3) >> 1)) * n, state->stack+(state->stackoffset-1)*n, n);
428 }
429 }
430 setTreeHeight(node_addr, state->stacklevels[state->stackoffset-1]);
431 setTreeIndex(node_addr, (idx >> (state->stacklevels[state->stackoffset-1]+1)));
432 hash_h(state->stack+(state->stackoffset-2)*n, state->stack+(state->stackoffset-2)*n, pub_seed, node_addr, n);
433
434 state->stacklevels[state->stackoffset-2]++;
435 state->stackoffset--;
436 }
437 state->next_leaf++;
438 return 0;
439}
440
441/**
442 * Returns the auth path for node leaf_idx and computes the auth path for the
443 * next leaf node, using the algorithm described by Buchmann, Dahmen and Szydlo
444 * in "Post Quantum Cryptography", Springer 2009.
445 */
446static 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])
447{
448 unsigned int i;
449 unsigned int n = params->n;
450 unsigned int h = params->h;
451 unsigned int k = params->k;
452
453 unsigned int tau = h;
454 unsigned int startidx;
455 unsigned int offset, rowidx;
456 unsigned char buf[2 * n];
457
458 uint32_t ots_addr[8];
459 uint32_t ltree_addr[8];
460 uint32_t node_addr[8];
461 // only copy layer and tree address parts
462 memcpy(ots_addr, addr, 12);
463 // type = ots
464 setType(ots_addr, 0);
465 memcpy(ltree_addr, addr, 12);
466 setType(ltree_addr, 1);
467 memcpy(node_addr, addr, 12);
468 setType(node_addr, 2);
469
470 for (i = 0; i < h; i++) {
471 if (! ((leaf_idx >> i) & 1)) {
472 tau = i;
473 break;
474 }
475 }
476
477 if (tau > 0) {
478 memcpy(buf, state->auth + (tau-1) * n, n);
479 // we need to do this before refreshing state->keep to prevent overwriting
480 memcpy(buf + n, state->keep + ((tau-1) >> 1) * n, n);
481 }
482 if (!((leaf_idx >> (tau + 1)) & 1) && (tau < h - 1)) {
483 memcpy(state->keep + (tau >> 1)*n, state->auth + tau*n, n);
484 }
485 if (tau == 0) {
486 setLtreeADRS(ltree_addr, leaf_idx);
487 setOTSADRS(ots_addr, leaf_idx);
488 gen_leaf_wots(state->auth, sk_seed, params, pub_seed, ltree_addr, ots_addr);
489 }
490 else {
491 setTreeHeight(node_addr, (tau-1));
492 setTreeIndex(node_addr, leaf_idx >> tau);
493 hash_h(state->auth + tau * n, buf, pub_seed, node_addr, n);
494 for (i = 0; i < tau; i++) {
495 if (i < h - k) {
496 memcpy(state->auth + i * n, state->treehash[i].node, n);
497 }
498 else {
499 offset = (1 << (h - 1 - i)) + i - h;
500 rowidx = ((leaf_idx >> i) - 1) >> 1;
501 memcpy(state->auth + i * n, state->retain + (offset + rowidx) * n, n);
502 }
503 }
504
505 for (i = 0; i < ((tau < h - k) ? tau : (h - k)); i++) {
506 startidx = leaf_idx + 1 + 3 * (1 << i);
507 if (startidx < 1U << h) {
508 state->treehash[i].h = i;
509 state->treehash[i].next_idx = startidx;
510 state->treehash[i].completed = 0;
511 state->treehash[i].stackusage = 0;
512 }
513 }
514 }
515}
516
517/*
518 * Generates a XMSS key pair for a given parameter set.
519 * Format sk: [(32bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
520 * Format pk: [root || PUB_SEED] omitting algo oid.
521 */
522int xmss_keypair(unsigned char *pk, unsigned char *sk, bds_state *state, xmss_params *params)
523{
524 unsigned int n = params->n;
525 // Set idx = 0
526 sk[0] = 0;
527 sk[1] = 0;
528 sk[2] = 0;
529 sk[3] = 0;
530 // Init SK_SEED (n byte), SK_PRF (n byte), and PUB_SEED (n byte)
531 randombytes(sk+4, 3*n);
532 // Copy PUB_SEED to public key
533 memcpy(pk+n, sk+4+2*n, n);
534
535 uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
536
537 // Compute root
538 treehash_setup(pk, params->h, 0, state, sk+4, params, sk+4+2*n, addr);
539 // copy root to sk
540 memcpy(sk+4+3*n, pk, n);
541 return 0;
542}
543
544/**
545 * Signs a message.
546 * Returns
547 * 1. an array containing the signature followed by the message AND
548 * 2. an updated secret key!
549 *
550 */
551int 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)
552{
553 unsigned int h = params->h;
554 unsigned int n = params->n;
555 unsigned int k = params->k;
556 uint16_t i = 0;
557
558 // Extract SK
559 unsigned long idx = ((unsigned long)sk[0] << 24) | ((unsigned long)sk[1] << 16) | ((unsigned long)sk[2] << 8) | sk[3];
560 unsigned char sk_seed[n];
561 memcpy(sk_seed, sk+4, n);
562 unsigned char sk_prf[n];
563 memcpy(sk_prf, sk+4+n, n);
564 unsigned char pub_seed[n];
565 memcpy(pub_seed, sk+4+2*n, n);
566
567 // index as 32 bytes string
568 unsigned char idx_bytes_32[32];
569 to_byte(idx_bytes_32, idx, 32);
570
571 unsigned char hash_key[3*n];
572
573 // Update SK
574 sk[0] = ((idx + 1) >> 24) & 255;
575 sk[1] = ((idx + 1) >> 16) & 255;
576 sk[2] = ((idx + 1) >> 8) & 255;
577 sk[3] = (idx + 1) & 255;
578 // -- Secret key for this non-forward-secure version is now updated.
579 // -- A productive implementation should use a file handle instead and write the updated secret key at this point!
580
581 // Init working params
582 unsigned char R[n];
583 unsigned char msg_h[n];
584 unsigned char ots_seed[n];
585 uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
586
587 // ---------------------------------
588 // Message Hashing
589 // ---------------------------------
590
591 // Message Hash:
592 // First compute pseudorandom value
593 prf(R, idx_bytes_32, sk_prf, n);
594 // Generate hash key (R || root || idx)
595 memcpy(hash_key, R, n);
596 memcpy(hash_key+n, sk+4+3*n, n);
597 to_byte(hash_key+2*n, idx, n);
598 // Then use it for message digest
599 h_msg(msg_h, msg, msglen, hash_key, 3*n, n);
600
601 // Start collecting signature
602 *sig_msg_len = 0;
603
604 // Copy index to signature
605 sig_msg[0] = (idx >> 24) & 255;
606 sig_msg[1] = (idx >> 16) & 255;
607 sig_msg[2] = (idx >> 8) & 255;
608 sig_msg[3] = idx & 255;
609
610 sig_msg += 4;
611 *sig_msg_len += 4;
612
613 // Copy R to signature
614 for (i = 0; i < n; i++)
615 sig_msg[i] = R[i];
616
617 sig_msg += n;
618 *sig_msg_len += n;
619
620 // ----------------------------------
621 // Now we start to "really sign"
622 // ----------------------------------
623
624 // Prepare Address
625 setType(ots_addr, 0);
626 setOTSADRS(ots_addr, idx);
627
628 // Compute seed for OTS key pair
629 get_seed(ots_seed, sk_seed, n, ots_addr);
630
631 // Compute WOTS signature
632 wots_sign(sig_msg, msg_h, ots_seed, &(params->wots_par), pub_seed, ots_addr);
633
634 sig_msg += params->wots_par.keysize;
635 *sig_msg_len += params->wots_par.keysize;
636
637 // the auth path was already computed during the previous round
638 memcpy(sig_msg, state->auth, h*n);
639
640 if (idx < (1U << h) - 1) {
641 bds_round(state, idx, sk_seed, params, pub_seed, ots_addr);
642 bds_treehash_update(state, (h - k) >> 1, sk_seed, params, pub_seed, ots_addr);
643 }
644
645/* TODO: save key/bds state here! */
646
647 sig_msg += params->h*n;
648 *sig_msg_len += params->h*n;
649
650 //Whipe secret elements?
651 //zerobytes(tsk, CRYPTO_SECRETKEYBYTES);
652
653
654 memcpy(sig_msg, msg, msglen);
655 *sig_msg_len += msglen;
656
657 return 0;
658}
659
660/**
661 * Verifies a given message signature pair under a given public key.
662 */
663int 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)
664{
665 unsigned int n = params->n;
666
667 unsigned long long i, m_len;
668 unsigned long idx=0;
669 unsigned char wots_pk[params->wots_par.keysize];
670 unsigned char pkhash[n];
671 unsigned char root[n];
672 unsigned char msg_h[n];
673 unsigned char hash_key[3*n];
674
675 unsigned char pub_seed[n];
676 memcpy(pub_seed, pk+n, n);
677
678 // Init addresses
679 uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
680 uint32_t ltree_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
681 uint32_t node_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
682
683 setType(ots_addr, 0);
684 setType(ltree_addr, 1);
685 setType(node_addr, 2);
686
687 // Extract index
688 idx = ((unsigned long)sig_msg[0] << 24) | ((unsigned long)sig_msg[1] << 16) | ((unsigned long)sig_msg[2] << 8) | sig_msg[3];
689 printf("verify:: idx = %lu\n", idx);
690
691 // Generate hash key (R || root || idx)
692 memcpy(hash_key, sig_msg+4,n);
693 memcpy(hash_key+n, pk, n);
694 to_byte(hash_key+2*n, idx, n);
695
696 sig_msg += (n+4);
697 sig_msg_len -= (n+4);
698
699 // hash message
700 unsigned long long tmp_sig_len = params->wots_par.keysize+params->h*n;
701 m_len = sig_msg_len - tmp_sig_len;
702 h_msg(msg_h, sig_msg + tmp_sig_len, m_len, hash_key, 3*n, n);
703
704 //-----------------------
705 // Verify signature
706 //-----------------------
707
708 // Prepare Address
709 setOTSADRS(ots_addr, idx);
710 // Check WOTS signature
711 wots_pkFromSig(wots_pk, sig_msg, msg_h, &(params->wots_par), pub_seed, ots_addr);
712
713 sig_msg += params->wots_par.keysize;
714 sig_msg_len -= params->wots_par.keysize;
715
716 // Compute Ltree
717 setLtreeADRS(ltree_addr, idx);
718 l_tree(pkhash, wots_pk, params, pub_seed, ltree_addr);
719
720 // Compute root
721 validate_authpath(root, pkhash, idx, sig_msg, params, pub_seed, node_addr);
722
723 sig_msg += params->h*n;
724 sig_msg_len -= params->h*n;
725
726 for (i = 0; i < n; i++)
727 if (root[i] != pk[i])
728 goto fail;
729
730 *msglen = sig_msg_len;
731 for (i = 0; i < *msglen; i++)
732 msg[i] = sig_msg[i];
733
734 return 0;
735
736
737fail:
738 *msglen = sig_msg_len;
739 for (i = 0; i < *msglen; i++)
740 msg[i] = 0;
741 *msglen = -1;
742 return -1;
743}
744
745/*
746 * Generates a XMSSMT key pair for a given parameter set.
747 * Format sk: [(ceil(h/8) bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
748 * Format pk: [root || PUB_SEED] omitting algo oid.
749 */
750int xmssmt_keypair(unsigned char *pk, unsigned char *sk, bds_state *states, unsigned char *wots_sigs, xmssmt_params *params)
751{
752 unsigned int n = params->n;
753 unsigned int i;
754 unsigned char ots_seed[params->n];
755 // Set idx = 0
756 for (i = 0; i < params->index_len; i++) {
757 sk[i] = 0;
758 }
759 // Init SK_SEED (n byte), SK_PRF (n byte), and PUB_SEED (n byte)
760 randombytes(sk+params->index_len, 3*n);
761 // Copy PUB_SEED to public key
762 memcpy(pk+n, sk+params->index_len+2*n, n);
763
764 // Set address to point on the single tree on layer d-1
765 uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
766 setLayerADRS(addr, (params->d-1));
767 // Set up state and compute wots signatures for all but topmost tree root
768 for (i = 0; i < params->d - 1; i++) {
769 // Compute seed for OTS key pair
770 treehash_setup(pk, params->xmss_par.h, 0, states + i, sk+params->index_len, &(params->xmss_par), pk+n, addr);
771 setLayerADRS(addr, (i+1));
772 get_seed(ots_seed, sk+params->index_len, n, addr);
773 wots_sign(wots_sigs + i*params->xmss_par.wots_par.keysize, pk, ots_seed, &(params->xmss_par.wots_par), pk+n, addr);
774 }
775 treehash_setup(pk, params->xmss_par.h, 0, states + i, sk+params->index_len, &(params->xmss_par), pk+n, addr);
776 memcpy(sk+params->index_len+3*n, pk, n);
777 return 0;
778}
779
780/**
781 * Signs a message.
782 * Returns
783 * 1. an array containing the signature followed by the message AND
784 * 2. an updated secret key!
785 *
786 */
787int 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)
788{
789 unsigned int n = params->n;
790
791 unsigned int tree_h = params->xmss_par.h;
792 unsigned int h = params->h;
793 unsigned int k = params->xmss_par.k;
794 unsigned int idx_len = params->index_len;
795 uint64_t idx_tree;
796 uint32_t idx_leaf;
797 uint64_t i, j;
798 int needswap_upto = -1;
799 unsigned int updates;
800
801 unsigned char sk_seed[n];
802 unsigned char sk_prf[n];
803 unsigned char pub_seed[n];
804 // Init working params
805 unsigned char R[n];
806 unsigned char msg_h[n];
807 unsigned char hash_key[3*n];
808 unsigned char ots_seed[n];
809 uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
810 uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
811 unsigned char idx_bytes_32[32];
812 bds_state tmp;
813
814 // Extract SK
815 unsigned long long idx = 0;
816 for (i = 0; i < idx_len; i++) {
817 idx |= ((unsigned long long)sk[i]) << 8*(idx_len - 1 - i);
818 }
819
820 memcpy(sk_seed, sk+idx_len, n);
821 memcpy(sk_prf, sk+idx_len+n, n);
822 memcpy(pub_seed, sk+idx_len+2*n, n);
823
824 // Update SK
825 for (i = 0; i < idx_len; i++) {
826 sk[i] = ((idx + 1) >> 8*(idx_len - 1 - i)) & 255;
827 }
828 // -- Secret key for this non-forward-secure version is now updated.
829 // -- A productive implementation should use a file handle instead and write the updated secret key at this point!
830
831
832 // ---------------------------------
833 // Message Hashing
834 // ---------------------------------
835
836 // Message Hash:
837 // First compute pseudorandom value
838 to_byte(idx_bytes_32, idx, 32);
839 prf(R, idx_bytes_32, sk_prf, n);
840 // Generate hash key (R || root || idx)
841 memcpy(hash_key, R, n);
842 memcpy(hash_key+n, sk+idx_len+3*n, n);
843 to_byte(hash_key+2*n, idx, n);
844
845 // Then use it for message digest
846 h_msg(msg_h, msg, msglen, hash_key, 3*n, n);
847
848 // Start collecting signature
849 *sig_msg_len = 0;
850
851 // Copy index to signature
852 for (i = 0; i < idx_len; i++) {
853 sig_msg[i] = (idx >> 8*(idx_len - 1 - i)) & 255;
854 }
855
856 sig_msg += idx_len;
857 *sig_msg_len += idx_len;
858
859 // Copy R to signature
860 for (i = 0; i < n; i++)
861 sig_msg[i] = R[i];
862
863 sig_msg += n;
864 *sig_msg_len += n;
865
866 // ----------------------------------
867 // Now we start to "really sign"
868 // ----------------------------------
869
870 // Handle lowest layer separately as it is slightly different...
871
872 // Prepare Address
873 setType(ots_addr, 0);
874 idx_tree = idx >> tree_h;
875 idx_leaf = (idx & ((1 << tree_h)-1));
876 setLayerADRS(ots_addr, 0);
877 setTreeADRS(ots_addr, idx_tree);
878 setOTSADRS(ots_addr, idx_leaf);
879
880 // Compute seed for OTS key pair
881 get_seed(ots_seed, sk_seed, n, ots_addr);
882
883 // Compute WOTS signature
884 wots_sign(sig_msg, msg_h, ots_seed, &(params->xmss_par.wots_par), pub_seed, ots_addr);
885
886 sig_msg += params->xmss_par.wots_par.keysize;
887 *sig_msg_len += params->xmss_par.wots_par.keysize;
888
889 memcpy(sig_msg, states[0].auth, tree_h*n);
890 sig_msg += tree_h*n;
891 *sig_msg_len += tree_h*n;
892
893 // prepare signature of remaining layers
894 for (i = 1; i < params->d; i++) {
895 // put WOTS signature in place
896 memcpy(sig_msg, wots_sigs + (i-1)*params->xmss_par.wots_par.keysize, params->xmss_par.wots_par.keysize);
897
898 sig_msg += params->xmss_par.wots_par.keysize;
899 *sig_msg_len += params->xmss_par.wots_par.keysize;
900
901 // put AUTH nodes in place
902 memcpy(sig_msg, states[i].auth, tree_h*n);
903 sig_msg += tree_h*n;
904 *sig_msg_len += tree_h*n;
905 }
906
907 updates = (tree_h - k) >> 1;
908
909 setTreeADRS(addr, (idx_tree + 1));
910 // mandatory update for NEXT_0 (does not count towards h-k/2) if NEXT_0 exists
911 if ((1 + idx_tree) * (1 << tree_h) + idx_leaf < (1ULL << h)) {
912 bds_state_update(&states[params->d], sk_seed, &(params->xmss_par), pub_seed, addr);
913 }
914
915 for (i = 0; i < params->d; i++) {
916 // check if we're not at the end of a tree
917 if (! (((idx + 1) & ((1ULL << ((i+1)*tree_h)) - 1)) == 0)) {
918 idx_leaf = (idx >> (tree_h * i)) & ((1 << tree_h)-1);
919 idx_tree = (idx >> (tree_h * (i+1)));
920 setLayerADRS(addr, i);
921 setTreeADRS(addr, idx_tree);
922 if (i == (unsigned int) (needswap_upto + 1)) {
923 bds_round(&states[i], idx_leaf, sk_seed, &(params->xmss_par), pub_seed, addr);
924 }
925 updates = bds_treehash_update(&states[i], updates, sk_seed, &(params->xmss_par), pub_seed, addr);
926 setTreeADRS(addr, (idx_tree + 1));
927 // if a NEXT-tree exists for this level;
928 if ((1 + idx_tree) * (1 << tree_h) + idx_leaf < (1ULL << (h - tree_h * i))) {
929 if (i > 0 && updates > 0 && states[params->d + i].next_leaf < (1ULL << h)) {
930 bds_state_update(&states[params->d + i], sk_seed, &(params->xmss_par), pub_seed, addr);
931 updates--;
932 }
933 }
934 }
935 else if (idx < (1ULL << h) - 1) {
936 memcpy(&tmp, states+params->d + i, sizeof(bds_state));
937 memcpy(states+params->d + i, states + i, sizeof(bds_state));
938 memcpy(states + i, &tmp, sizeof(bds_state));
939
940 setLayerADRS(ots_addr, (i+1));
941 setTreeADRS(ots_addr, ((idx + 1) >> ((i+2) * tree_h)));
942 setOTSADRS(ots_addr, (((idx >> ((i+1) * tree_h)) + 1) & ((1 << tree_h)-1)));
943
944 get_seed(ots_seed, sk+params->index_len, n, ots_addr);
945 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);
946
947 states[params->d + i].stackoffset = 0;
948 states[params->d + i].next_leaf = 0;
949
950 updates--; // WOTS-signing counts as one update
951 needswap_upto = i;
952 for (j = 0; j < tree_h-k; j++) {
953 states[i].treehash[j].completed = 1;
954 }
955 }
956 }
957
958 //Whipe secret elements?
959 //zerobytes(tsk, CRYPTO_SECRETKEYBYTES);
960
961 memcpy(sig_msg, msg, msglen);
962 *sig_msg_len += msglen;
963
964 return 0;
965}
966
967/**
968 * Verifies a given message signature pair under a given public key.
969 */
970int 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)
971{
972 unsigned int n = params->n;
973
974 unsigned int tree_h = params->xmss_par.h;
975 unsigned int idx_len = params->index_len;
976 uint64_t idx_tree;
977 uint32_t idx_leaf;
978
979 unsigned long long i, m_len;
980 unsigned long long idx=0;
981 unsigned char wots_pk[params->xmss_par.wots_par.keysize];
982 unsigned char pkhash[n];
983 unsigned char root[n];
984 unsigned char msg_h[n];
985 unsigned char hash_key[3*n];
986
987 unsigned char pub_seed[n];
988 memcpy(pub_seed, pk+n, n);
989
990 // Init addresses
991 uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
992 uint32_t ltree_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
993 uint32_t node_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
994
995 // Extract index
996 for (i = 0; i < idx_len; i++) {
997 idx |= ((unsigned long long)sig_msg[i]) << (8*(idx_len - 1 - i));
998 }
999 printf("verify:: idx = %llu\n", idx);
1000 sig_msg += idx_len;
1001 sig_msg_len -= idx_len;
1002
1003 // Generate hash key (R || root || idx)
1004 memcpy(hash_key, sig_msg,n);
1005 memcpy(hash_key+n, pk, n);
1006 to_byte(hash_key+2*n, idx, n);
1007
1008 sig_msg += n;
1009 sig_msg_len -= n;
1010
1011
1012 // hash message (recall, R is now on pole position at sig_msg
1013 unsigned long long tmp_sig_len = (params->d * params->xmss_par.wots_par.keysize) + (params->h * n);
1014 m_len = sig_msg_len - tmp_sig_len;
1015 h_msg(msg_h, sig_msg + tmp_sig_len, m_len, hash_key, 3*n, n);
1016
1017
1018 //-----------------------
1019 // Verify signature
1020 //-----------------------
1021
1022 // Prepare Address
1023 idx_tree = idx >> tree_h;
1024 idx_leaf = (idx & ((1 << tree_h)-1));
1025 setLayerADRS(ots_addr, 0);
1026 setTreeADRS(ots_addr, idx_tree);
1027 setType(ots_addr, 0);
1028
1029 memcpy(ltree_addr, ots_addr, 12);
1030 setType(ltree_addr, 1);
1031
1032 memcpy(node_addr, ltree_addr, 12);
1033 setType(node_addr, 2);
1034
1035 setOTSADRS(ots_addr, idx_leaf);
1036
1037 // Check WOTS signature
1038 wots_pkFromSig(wots_pk, sig_msg, msg_h, &(params->xmss_par.wots_par), pub_seed, ots_addr);
1039
1040 sig_msg += params->xmss_par.wots_par.keysize;
1041 sig_msg_len -= params->xmss_par.wots_par.keysize;
1042
1043 // Compute Ltree
1044 setLtreeADRS(ltree_addr, idx_leaf);
1045 l_tree(pkhash, wots_pk, &(params->xmss_par), pub_seed, ltree_addr);
1046
1047 // Compute root
1048 validate_authpath(root, pkhash, idx_leaf, sig_msg, &(params->xmss_par), pub_seed, node_addr);
1049
1050 sig_msg += tree_h*n;
1051 sig_msg_len -= tree_h*n;
1052
1053 for (i = 1; i < params->d; i++) {
1054 // Prepare Address
1055 idx_leaf = (idx_tree & ((1 << tree_h)-1));
1056 idx_tree = idx_tree >> tree_h;
1057
1058 setLayerADRS(ots_addr, i);
1059 setTreeADRS(ots_addr, idx_tree);
1060 setType(ots_addr, 0);
1061
1062 memcpy(ltree_addr, ots_addr, 12);
1063 setType(ltree_addr, 1);
1064
1065 memcpy(node_addr, ltree_addr, 12);
1066 setType(node_addr, 2);
1067
1068 setOTSADRS(ots_addr, idx_leaf);
1069
1070 // Check WOTS signature
1071 wots_pkFromSig(wots_pk, sig_msg, root, &(params->xmss_par.wots_par), pub_seed, ots_addr);
1072
1073 sig_msg += params->xmss_par.wots_par.keysize;
1074 sig_msg_len -= params->xmss_par.wots_par.keysize;
1075
1076 // Compute Ltree
1077 setLtreeADRS(ltree_addr, idx_leaf);
1078 l_tree(pkhash, wots_pk, &(params->xmss_par), pub_seed, ltree_addr);
1079
1080 // Compute root
1081 validate_authpath(root, pkhash, idx_leaf, sig_msg, &(params->xmss_par), pub_seed, node_addr);
1082
1083 sig_msg += tree_h*n;
1084 sig_msg_len -= tree_h*n;
1085
1086 }
1087
1088 for (i = 0; i < n; i++)
1089 if (root[i] != pk[i])
1090 goto fail;
1091
1092 *msglen = sig_msg_len;
1093 for (i = 0; i < *msglen; i++)
1094 msg[i] = sig_msg[i];
1095
1096 return 0;
1097
1098
1099fail:
1100 *msglen = sig_msg_len;
1101 for (i = 0; i < *msglen; i++)
1102 msg[i] = 0;
1103 *msglen = -1;
1104 return -1;
1105}
Darren Tuckera10d8552018-02-27 14:45:17 +11001106#endif /* WITH_XMSS */