1 /* Copyright (c) 2023, Google LLC
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15 #include <openssl/base.h>
16
17 #include <string.h>
18
19 #include <openssl/rand.h>
20
21 #include "./address.h"
22 #include "./fors.h"
23 #include "./internal.h"
24 #include "./merkle.h"
25 #include "./params.h"
26 #include "./spx_util.h"
27 #include "./thash.h"
28
spx_generate_key(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],uint8_t out_secret_key[SPX_SECRET_KEY_BYTES])29 void spx_generate_key(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],
30 uint8_t out_secret_key[SPX_SECRET_KEY_BYTES]) {
31 uint8_t seed[3 * SPX_N];
32 RAND_bytes(seed, 3 * SPX_N);
33 spx_generate_key_from_seed(out_public_key, out_secret_key, seed);
34 }
35
spx_generate_key_from_seed(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],uint8_t out_secret_key[SPX_SECRET_KEY_BYTES],const uint8_t seed[3* SPX_N])36 void spx_generate_key_from_seed(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],
37 uint8_t out_secret_key[SPX_SECRET_KEY_BYTES],
38 const uint8_t seed[3 * SPX_N]) {
39 // Initialize SK.seed || SK.prf || PK.seed from seed.
40 memcpy(out_secret_key, seed, 3 * SPX_N);
41
42 // Initialize PK.seed from seed.
43 memcpy(out_public_key, seed + 2 * SPX_N, SPX_N);
44
45 uint8_t addr[32] = {0};
46 spx_set_layer_addr(addr, SPX_D - 1);
47
48 // Set PK.root
49 spx_treehash(out_public_key + SPX_N, out_secret_key, 0, SPX_TREE_HEIGHT,
50 out_public_key, addr);
51 memcpy(out_secret_key + 3 * SPX_N, out_public_key + SPX_N, SPX_N);
52 }
53
spx_sign(uint8_t out_signature[SPX_SIGNATURE_BYTES],const uint8_t secret_key[SPX_SECRET_KEY_BYTES],const uint8_t * msg,size_t msg_len,int randomized)54 void spx_sign(uint8_t out_signature[SPX_SIGNATURE_BYTES],
55 const uint8_t secret_key[SPX_SECRET_KEY_BYTES],
56 const uint8_t *msg, size_t msg_len, int randomized) {
57 uint8_t addr[32] = {0};
58 const uint8_t *sk_seed = secret_key;
59 const uint8_t *sk_prf = secret_key + SPX_N;
60 const uint8_t *pk_seed = secret_key + 2 * SPX_N;
61 const uint8_t *pk_root = secret_key + 3 * SPX_N;
62
63 uint8_t opt_rand[SPX_N] = {0};
64
65 if (randomized) {
66 RAND_bytes(opt_rand, SPX_N);
67 } else {
68 memcpy(opt_rand, pk_seed, SPX_N);
69 }
70
71 // Derive randomizer r and copy it to signature.
72 uint8_t r[SPX_N];
73 spx_thash_prfmsg(r, sk_prf, opt_rand, msg, msg_len);
74 memcpy(out_signature, r, SPX_N);
75
76 uint8_t digest[SPX_DIGEST_SIZE];
77 spx_thash_hmsg(digest, r, pk_seed, pk_root, msg, msg_len);
78
79 uint8_t fors_digest[SPX_FORS_MSG_BYTES];
80 memcpy(fors_digest, digest, SPX_FORS_MSG_BYTES);
81
82 uint8_t *tmp_idx_tree = digest + SPX_FORS_MSG_BYTES;
83 uint8_t *tmp_idx_leaf = tmp_idx_tree + SPX_TREE_BYTES;
84
85 uint64_t idx_tree = spx_to_uint64(tmp_idx_tree, SPX_TREE_BYTES);
86 idx_tree &= (~(uint64_t)0) >> (64 - SPX_TREE_BITS);
87
88 uint32_t idx_leaf = (uint32_t)spx_to_uint64(tmp_idx_leaf, SPX_LEAF_BYTES);
89 idx_leaf &= (~(uint32_t)0) >> (32 - SPX_LEAF_BITS);
90
91 spx_set_tree_addr(addr, idx_tree);
92 spx_set_type(addr, SPX_ADDR_TYPE_FORSTREE);
93 spx_set_keypair_addr(addr, idx_leaf);
94
95 spx_fors_sign(out_signature + SPX_N, fors_digest, sk_seed, pk_seed, addr);
96
97 uint8_t pk_fors[SPX_N];
98 spx_fors_pk_from_sig(pk_fors, out_signature + SPX_N, fors_digest, pk_seed,
99 addr);
100
101 spx_ht_sign(out_signature + SPX_N + SPX_FORS_BYTES, pk_fors, idx_tree,
102 idx_leaf, sk_seed, pk_seed);
103 }
104
spx_verify(const uint8_t signature[SPX_SIGNATURE_BYTES],const uint8_t public_key[SPX_SECRET_KEY_BYTES],const uint8_t * msg,size_t msg_len)105 int spx_verify(const uint8_t signature[SPX_SIGNATURE_BYTES],
106 const uint8_t public_key[SPX_SECRET_KEY_BYTES],
107 const uint8_t *msg, size_t msg_len) {
108 uint8_t addr[32] = {0};
109 const uint8_t *pk_seed = public_key;
110 const uint8_t *pk_root = public_key + SPX_N;
111
112 const uint8_t *r = signature;
113 const uint8_t *sig_fors = signature + SPX_N;
114 const uint8_t *sig_ht = sig_fors + SPX_FORS_BYTES;
115
116 uint8_t digest[SPX_DIGEST_SIZE];
117 spx_thash_hmsg(digest, r, pk_seed, pk_root, msg, msg_len);
118
119 uint8_t fors_digest[SPX_FORS_MSG_BYTES];
120 memcpy(fors_digest, digest, SPX_FORS_MSG_BYTES);
121
122 uint8_t *tmp_idx_tree = digest + SPX_FORS_MSG_BYTES;
123 uint8_t *tmp_idx_leaf = tmp_idx_tree + SPX_TREE_BYTES;
124
125 uint64_t idx_tree = spx_to_uint64(tmp_idx_tree, SPX_TREE_BYTES);
126 idx_tree &= (~(uint64_t)0) >> (64 - SPX_TREE_BITS);
127
128 uint32_t idx_leaf = (uint32_t)spx_to_uint64(tmp_idx_leaf, SPX_LEAF_BYTES);
129 idx_leaf &= (~(uint32_t)0) >> (32 - SPX_LEAF_BITS);
130
131 spx_set_tree_addr(addr, idx_tree);
132 spx_set_type(addr, SPX_ADDR_TYPE_FORSTREE);
133 spx_set_keypair_addr(addr, idx_leaf);
134
135 uint8_t pk_fors[SPX_N];
136 spx_fors_pk_from_sig(pk_fors, sig_fors, fors_digest, pk_seed, addr);
137
138 return spx_ht_verify(sig_ht, pk_fors, idx_tree, idx_leaf, pk_root, pk_seed);
139 }
140