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 #define OPENSSL_UNSTABLE_EXPERIMENTAL_SPX
20 #include <openssl/experimental/spx.h>
21 #include <openssl/rand.h>
22
23 #include "./address.h"
24 #include "./fors.h"
25 #include "./merkle.h"
26 #include "./params.h"
27 #include "./spx_util.h"
28 #include "./thash.h"
29
SPX_generate_key(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],uint8_t out_secret_key[SPX_SECRET_KEY_BYTES])30 void SPX_generate_key(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],
31 uint8_t out_secret_key[SPX_SECRET_KEY_BYTES]) {
32 uint8_t seed[3 * SPX_N];
33 RAND_bytes(seed, 3 * SPX_N);
34 SPX_generate_key_from_seed(out_public_key, out_secret_key, seed);
35 }
36
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])37 void SPX_generate_key_from_seed(uint8_t out_public_key[SPX_PUBLIC_KEY_BYTES],
38 uint8_t out_secret_key[SPX_SECRET_KEY_BYTES],
39 const uint8_t seed[3 * SPX_N]) {
40 // Initialize SK.seed || SK.prf || PK.seed from seed.
41 memcpy(out_secret_key, seed, 3 * SPX_N);
42
43 // Initialize PK.seed from seed.
44 memcpy(out_public_key, seed + 2 * SPX_N, SPX_N);
45
46 uint8_t addr[32] = {0};
47 spx_set_layer_addr(addr, SPX_D - 1);
48
49 // Set PK.root
50 spx_treehash(out_public_key + SPX_N, out_secret_key, 0, SPX_TREE_HEIGHT,
51 out_public_key, addr);
52 memcpy(out_secret_key + 3 * SPX_N, out_public_key + SPX_N, SPX_N);
53 }
54
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)55 void SPX_sign(uint8_t out_signature[SPX_SIGNATURE_BYTES],
56 const uint8_t secret_key[SPX_SECRET_KEY_BYTES],
57 const uint8_t *msg, size_t msg_len, int randomized) {
58 uint8_t addr[32] = {0};
59 const uint8_t *sk_seed = secret_key;
60 const uint8_t *sk_prf = secret_key + SPX_N;
61 const uint8_t *pk_seed = secret_key + 2 * SPX_N;
62 const uint8_t *pk_root = secret_key + 3 * SPX_N;
63
64 uint8_t opt_rand[SPX_N] = {0};
65
66 if (randomized) {
67 RAND_bytes(opt_rand, SPX_N);
68 } else {
69 memcpy(opt_rand, pk_seed, SPX_N);
70 }
71
72 // Derive randomizer r and copy it to signature.
73 uint8_t r[SPX_N];
74 spx_thash_prfmsg(r, sk_prf, opt_rand, msg, msg_len);
75 memcpy(out_signature, r, SPX_N);
76
77 uint8_t digest[SPX_DIGEST_SIZE];
78 spx_thash_hmsg(digest, r, pk_seed, pk_root, msg, msg_len);
79
80 uint8_t fors_digest[SPX_FORS_MSG_BYTES];
81 memcpy(fors_digest, digest, SPX_FORS_MSG_BYTES);
82
83 uint8_t *tmp_idx_tree = digest + SPX_FORS_MSG_BYTES;
84 uint8_t *tmp_idx_leaf = tmp_idx_tree + SPX_TREE_BYTES;
85
86 uint64_t idx_tree = spx_to_uint64(tmp_idx_tree, SPX_TREE_BYTES);
87 idx_tree &= (~(uint64_t)0) >> (64 - SPX_TREE_BITS);
88
89 uint32_t idx_leaf = (uint32_t)spx_to_uint64(tmp_idx_leaf, SPX_LEAF_BYTES);
90 idx_leaf &= (~(uint32_t)0) >> (32 - SPX_LEAF_BITS);
91
92 spx_set_tree_addr(addr, idx_tree);
93 spx_set_type(addr, SPX_ADDR_TYPE_FORSTREE);
94 spx_set_keypair_addr(addr, idx_leaf);
95
96 spx_fors_sign(out_signature + SPX_N, fors_digest, sk_seed, pk_seed, addr);
97
98 uint8_t pk_fors[SPX_N];
99 spx_fors_pk_from_sig(pk_fors, out_signature + SPX_N, fors_digest, pk_seed,
100 addr);
101
102 spx_ht_sign(out_signature + SPX_N + SPX_FORS_BYTES, pk_fors, idx_tree,
103 idx_leaf, sk_seed, pk_seed);
104 }
105
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)106 int SPX_verify(const uint8_t signature[SPX_SIGNATURE_BYTES],
107 const uint8_t public_key[SPX_SECRET_KEY_BYTES],
108 const uint8_t *msg, size_t msg_len) {
109 uint8_t addr[32] = {0};
110 const uint8_t *pk_seed = public_key;
111 const uint8_t *pk_root = public_key + SPX_N;
112
113 const uint8_t *r = signature;
114 const uint8_t *sig_fors = signature + SPX_N;
115 const uint8_t *sig_ht = sig_fors + SPX_FORS_BYTES;
116
117 uint8_t digest[SPX_DIGEST_SIZE];
118 spx_thash_hmsg(digest, r, pk_seed, pk_root, msg, msg_len);
119
120 uint8_t fors_digest[SPX_FORS_MSG_BYTES];
121 memcpy(fors_digest, digest, SPX_FORS_MSG_BYTES);
122
123 uint8_t *tmp_idx_tree = digest + SPX_FORS_MSG_BYTES;
124 uint8_t *tmp_idx_leaf = tmp_idx_tree + SPX_TREE_BYTES;
125
126 uint64_t idx_tree = spx_to_uint64(tmp_idx_tree, SPX_TREE_BYTES);
127 idx_tree &= (~(uint64_t)0) >> (64 - SPX_TREE_BITS);
128
129 uint32_t idx_leaf = (uint32_t)spx_to_uint64(tmp_idx_leaf, SPX_LEAF_BYTES);
130 idx_leaf &= (~(uint32_t)0) >> (32 - SPX_LEAF_BITS);
131
132 spx_set_tree_addr(addr, idx_tree);
133 spx_set_type(addr, SPX_ADDR_TYPE_FORSTREE);
134 spx_set_keypair_addr(addr, idx_leaf);
135
136 uint8_t pk_fors[SPX_N];
137 spx_fors_pk_from_sig(pk_fors, sig_fors, fors_digest, pk_seed, addr);
138
139 return spx_ht_verify(sig_ht, pk_fors, idx_tree, idx_leaf, pk_root, pk_seed);
140 }
141