71757157036143a2e2c0c18685de1e57dfc90158
[openssl.git] / crypto / ec / curve448 / eddsa.c
1 /*
2  * Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved.
3  * Copyright 2015-2016 Cryptography Research, Inc.
4  *
5  * Licensed under the OpenSSL license (the "License").  You may not use
6  * this file except in compliance with the License.  You can obtain a copy
7  * in the file LICENSE in the source distribution or at
8  * https://www.openssl.org/source/license.html
9  *
10  * Originally written by Mike Hamburg
11  */
12 #include <string.h>
13 #include <openssl/crypto.h>
14 #include <openssl/evp.h>
15 #include "curve448_lcl.h"
16 #include "word.h"
17 #include "ed448.h"
18 #include "internal/numbers.h"
19
20 #define COFACTOR 4
21
22 static c448_error_t oneshot_hash(uint8_t *out, size_t outlen,
23                                  const uint8_t *in, size_t inlen)
24 {
25     EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
26
27     if (hashctx == NULL)
28         return C448_FAILURE;
29
30     if (!EVP_DigestInit_ex(hashctx, EVP_shake256(), NULL)
31             || !EVP_DigestUpdate(hashctx, in, inlen)
32             || !EVP_DigestFinalXOF(hashctx, out, outlen)) {
33         EVP_MD_CTX_free(hashctx);
34         return C448_FAILURE;
35     }
36
37     EVP_MD_CTX_free(hashctx);
38     return C448_SUCCESS;
39 }
40
41 static void clamp(uint8_t secret_scalar_ser[EDDSA_448_PRIVATE_BYTES])
42 {
43     secret_scalar_ser[0] &= -COFACTOR;
44     secret_scalar_ser[EDDSA_448_PRIVATE_BYTES - 1] = 0;
45     secret_scalar_ser[EDDSA_448_PRIVATE_BYTES - 2] |= 0x80;
46 }
47
48 static c448_error_t hash_init_with_dom(EVP_MD_CTX *hashctx, uint8_t prehashed,
49                                        uint8_t for_prehash,
50                                        const uint8_t *context,
51                                        size_t context_len)
52 {
53     const char *dom_s = "SigEd448";
54     uint8_t dom[2];
55
56     if (context_len > UINT8_MAX)
57         return C448_FAILURE;
58
59     dom[0] = (uint8_t)(2 - (prehashed == 0 ? 1 : 0)
60                        - (for_prehash == 0 ? 1 : 0));
61     dom[1] = (uint8_t)context_len;
62
63     if (!EVP_DigestInit_ex(hashctx, EVP_shake256(), NULL)
64             || !EVP_DigestUpdate(hashctx, dom_s, strlen(dom_s))
65             || !EVP_DigestUpdate(hashctx, dom, sizeof(dom))
66             || !EVP_DigestUpdate(hashctx, context, context_len))
67         return C448_FAILURE;
68
69     return C448_SUCCESS;
70 }
71
72 /* In this file because it uses the hash */
73 c448_error_t c448_ed448_convert_private_key_to_x448(
74                             uint8_t x[X448_PRIVATE_BYTES],
75                             const uint8_t ed [EDDSA_448_PRIVATE_BYTES])
76 {
77     /* pass the private key through oneshot_hash function */
78     /* and keep the first X448_PRIVATE_BYTES bytes */
79     return oneshot_hash(x, X448_PRIVATE_BYTES, ed,
80                         EDDSA_448_PRIVATE_BYTES);
81 }
82
83 c448_error_t c448_ed448_derive_public_key(
84                         uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
85                         const uint8_t privkey[EDDSA_448_PRIVATE_BYTES])
86 {
87     /* only this much used for keygen */
88     uint8_t secret_scalar_ser[EDDSA_448_PRIVATE_BYTES];
89     curve448_scalar_t secret_scalar;
90     unsigned int c;
91     curve448_point_t p;
92
93     if (!oneshot_hash(secret_scalar_ser, sizeof(secret_scalar_ser), privkey,
94                       EDDSA_448_PRIVATE_BYTES))
95         return C448_FAILURE;
96
97     clamp(secret_scalar_ser);
98
99     curve448_scalar_decode_long(secret_scalar, secret_scalar_ser,
100                                 sizeof(secret_scalar_ser));
101
102     /*
103      * Since we are going to mul_by_cofactor during encoding, divide by it
104      * here. However, the EdDSA base point is not the same as the decaf base
105      * point if the sigma isogeny is in use: the EdDSA base point is on
106      * Etwist_d/(1-d) and the decaf base point is on Etwist_d, and when
107      * converted it effectively picks up a factor of 2 from the isogenies.  So
108      * we might start at 2 instead of 1.
109      */
110     for (c = 1; c < C448_EDDSA_ENCODE_RATIO; c <<= 1)
111         curve448_scalar_halve(secret_scalar, secret_scalar);
112
113     curve448_precomputed_scalarmul(p, curve448_precomputed_base, secret_scalar);
114
115     curve448_point_mul_by_ratio_and_encode_like_eddsa(pubkey, p);
116
117     /* Cleanup */
118     curve448_scalar_destroy(secret_scalar);
119     curve448_point_destroy(p);
120     OPENSSL_cleanse(secret_scalar_ser, sizeof(secret_scalar_ser));
121
122     return C448_SUCCESS;
123 }
124
125 c448_error_t c448_ed448_sign(
126                         uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
127                         const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
128                         const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
129                         const uint8_t *message, size_t message_len,
130                         uint8_t prehashed, const uint8_t *context,
131                         size_t context_len)
132 {
133     curve448_scalar_t secret_scalar;
134     EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
135     c448_error_t ret = C448_FAILURE;
136     curve448_scalar_t nonce_scalar;
137     uint8_t nonce_point[EDDSA_448_PUBLIC_BYTES] = { 0 };
138     unsigned int c;
139     curve448_scalar_t challenge_scalar;
140
141     if (hashctx == NULL)
142         return C448_FAILURE;
143
144     {
145         /*
146          * Schedule the secret key, First EDDSA_448_PRIVATE_BYTES is serialised
147          * secret scalar,next EDDSA_448_PRIVATE_BYTES bytes is the seed.
148          */
149         uint8_t expanded[EDDSA_448_PRIVATE_BYTES * 2];
150
151         if (!oneshot_hash(expanded, sizeof(expanded), privkey,
152                           EDDSA_448_PRIVATE_BYTES))
153             goto err;
154         clamp(expanded);
155         curve448_scalar_decode_long(secret_scalar, expanded,
156                                     EDDSA_448_PRIVATE_BYTES);
157
158         /* Hash to create the nonce */
159         if (!hash_init_with_dom(hashctx, prehashed, 0, context, context_len)
160                 || !EVP_DigestUpdate(hashctx,
161                                      expanded + EDDSA_448_PRIVATE_BYTES,
162                                      EDDSA_448_PRIVATE_BYTES)
163                 || !EVP_DigestUpdate(hashctx, message, message_len)) {
164             OPENSSL_cleanse(expanded, sizeof(expanded));
165             goto err;
166         }
167         OPENSSL_cleanse(expanded, sizeof(expanded));
168     }
169
170     /* Decode the nonce */
171     {
172         uint8_t nonce[2 * EDDSA_448_PRIVATE_BYTES];
173
174         if (!EVP_DigestFinalXOF(hashctx, nonce, sizeof(nonce)))
175             goto err;
176         curve448_scalar_decode_long(nonce_scalar, nonce, sizeof(nonce));
177         OPENSSL_cleanse(nonce, sizeof(nonce));
178     }
179
180     {
181         /* Scalarmul to create the nonce-point */
182         curve448_scalar_t nonce_scalar_2;
183         curve448_point_t p;
184
185         curve448_scalar_halve(nonce_scalar_2, nonce_scalar);
186         for (c = 2; c < C448_EDDSA_ENCODE_RATIO; c <<= 1)
187             curve448_scalar_halve(nonce_scalar_2, nonce_scalar_2);
188
189         curve448_precomputed_scalarmul(p, curve448_precomputed_base,
190                                        nonce_scalar_2);
191         curve448_point_mul_by_ratio_and_encode_like_eddsa(nonce_point, p);
192         curve448_point_destroy(p);
193         curve448_scalar_destroy(nonce_scalar_2);
194     }
195
196     {
197         uint8_t challenge[2 * EDDSA_448_PRIVATE_BYTES];
198
199         /* Compute the challenge */
200         if (!hash_init_with_dom(hashctx, prehashed, 0, context, context_len)
201                 || !EVP_DigestUpdate(hashctx, nonce_point, sizeof(nonce_point))
202                 || !EVP_DigestUpdate(hashctx, pubkey, EDDSA_448_PUBLIC_BYTES)
203                 || !EVP_DigestUpdate(hashctx, message, message_len)
204                 || !EVP_DigestFinalXOF(hashctx, challenge, sizeof(challenge)))
205             goto err;
206
207         curve448_scalar_decode_long(challenge_scalar, challenge,
208                                     sizeof(challenge));
209         OPENSSL_cleanse(challenge, sizeof(challenge));
210     }
211
212     curve448_scalar_mul(challenge_scalar, challenge_scalar, secret_scalar);
213     curve448_scalar_add(challenge_scalar, challenge_scalar, nonce_scalar);
214
215     OPENSSL_cleanse(signature, EDDSA_448_SIGNATURE_BYTES);
216     memcpy(signature, nonce_point, sizeof(nonce_point));
217     curve448_scalar_encode(&signature[EDDSA_448_PUBLIC_BYTES],
218                            challenge_scalar);
219
220     curve448_scalar_destroy(secret_scalar);
221     curve448_scalar_destroy(nonce_scalar);
222     curve448_scalar_destroy(challenge_scalar);
223
224     ret = C448_SUCCESS;
225  err:
226     EVP_MD_CTX_free(hashctx);
227     return ret;
228 }
229
230 c448_error_t c448_ed448_sign_prehash(
231                         uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
232                         const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
233                         const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
234                         const uint8_t hash[64], const uint8_t *context,
235                         size_t context_len)
236 {
237     return c448_ed448_sign(signature, privkey, pubkey, hash, 64, 1, context,
238                            context_len);
239 }
240
241 c448_error_t c448_ed448_verify(
242                     const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
243                     const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
244                     const uint8_t *message, size_t message_len,
245                     uint8_t prehashed, const uint8_t *context,
246                     uint8_t context_len)
247 {
248     curve448_point_t pk_point, r_point;
249     c448_error_t error =
250         curve448_point_decode_like_eddsa_and_mul_by_ratio(pk_point, pubkey);
251     curve448_scalar_t challenge_scalar;
252     curve448_scalar_t response_scalar;
253     unsigned int c;
254
255     if (C448_SUCCESS != error)
256         return error;
257
258     error =
259         curve448_point_decode_like_eddsa_and_mul_by_ratio(r_point, signature);
260     if (C448_SUCCESS != error)
261         return error;
262
263     {
264         /* Compute the challenge */
265         EVP_MD_CTX *hashctx = EVP_MD_CTX_new();
266         uint8_t challenge[2 * EDDSA_448_PRIVATE_BYTES];
267
268         if (hashctx == NULL
269                 || !hash_init_with_dom(hashctx, prehashed, 0, context,
270                                        context_len)
271                 || !EVP_DigestUpdate(hashctx, signature, EDDSA_448_PUBLIC_BYTES)
272                 || !EVP_DigestUpdate(hashctx, pubkey, EDDSA_448_PUBLIC_BYTES)
273                 || !EVP_DigestUpdate(hashctx, message, message_len)
274                 || !EVP_DigestFinalXOF(hashctx, challenge, sizeof(challenge))) {
275             EVP_MD_CTX_free(hashctx);
276             return C448_FAILURE;
277         }
278
279         EVP_MD_CTX_free(hashctx);
280         curve448_scalar_decode_long(challenge_scalar, challenge,
281                                     sizeof(challenge));
282         OPENSSL_cleanse(challenge, sizeof(challenge));
283     }
284     curve448_scalar_sub(challenge_scalar, curve448_scalar_zero,
285                         challenge_scalar);
286
287     curve448_scalar_decode_long(response_scalar,
288                                 &signature[EDDSA_448_PUBLIC_BYTES],
289                                 EDDSA_448_PRIVATE_BYTES);
290
291     for (c = 1; c < C448_EDDSA_DECODE_RATIO; c <<= 1)
292         curve448_scalar_add(response_scalar, response_scalar, response_scalar);
293
294     /* pk_point = -c(x(P)) + (cx + k)G = kG */
295     curve448_base_double_scalarmul_non_secret(pk_point,
296                                               response_scalar,
297                                               pk_point, challenge_scalar);
298     return c448_succeed_if(curve448_point_eq(pk_point, r_point));
299 }
300
301 c448_error_t c448_ed448_verify_prehash(
302                     const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
303                     const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
304                     const uint8_t hash[64], const uint8_t *context,
305                     uint8_t context_len)
306 {
307     return c448_ed448_verify(signature, pubkey, hash, 64, 1, context,
308                              context_len);
309 }
310
311 int ED448_sign(uint8_t *out_sig, const uint8_t *message, size_t message_len,
312                const uint8_t public_key[57], const uint8_t private_key[57],
313                const uint8_t *context, size_t context_len)
314 {
315     return c448_ed448_sign(out_sig, private_key, public_key, message,
316                            message_len, 0, context, context_len)
317         == C448_SUCCESS;
318 }
319
320 int ED448_verify(const uint8_t *message, size_t message_len,
321                  const uint8_t signature[114], const uint8_t public_key[57],
322                  const uint8_t *context, size_t context_len)
323 {
324     return c448_ed448_verify(signature, public_key, message, message_len, 0,
325                              context, (uint8_t)context_len) == C448_SUCCESS;
326 }
327
328 int ED448ph_sign(uint8_t *out_sig, const uint8_t hash[64],
329                  const uint8_t public_key[57], const uint8_t private_key[57],
330                  const uint8_t *context, size_t context_len)
331 {
332     return c448_ed448_sign_prehash(out_sig, private_key, public_key, hash,
333                                    context, context_len) == C448_SUCCESS;
334
335 }
336
337 int ED448ph_verify(const uint8_t hash[64], const uint8_t signature[114],
338                    const uint8_t public_key[57], const uint8_t *context,
339                    size_t context_len)
340 {
341     return c448_ed448_verify_prehash(signature, public_key, hash, context,
342                                      (uint8_t)context_len) == C448_SUCCESS;
343 }
344
345 int ED448_public_from_private(uint8_t out_public_key[57],
346                               const uint8_t private_key[57])
347 {
348     return c448_ed448_derive_public_key(out_public_key, private_key)
349         == C448_SUCCESS;
350 }