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1308e022 | 1 | /* |
f53c7764 | 2 | * Copyright 2017-2018 The OpenSSL Project Authors. All Rights Reserved. |
1308e022 | 3 | * Copyright 2015-2016 Cryptography Research, Inc. |
7324473f | 4 | * |
1308e022 MC |
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 | |
7324473f | 9 | * |
1308e022 | 10 | * Originally written by Mike Hamburg |
7324473f MC |
11 | */ |
12 | ||
68b20c00 MC |
13 | #ifndef HEADER_ED448_H |
14 | # define HEADER_ED448_H | |
7324473f | 15 | |
205fd638 | 16 | # include "point_448.h" |
7324473f | 17 | |
8d55f844 | 18 | /* Number of bytes in an EdDSA public key. */ |
db90b274 | 19 | # define EDDSA_448_PUBLIC_BYTES 57 |
7324473f | 20 | |
8d55f844 | 21 | /* Number of bytes in an EdDSA private key. */ |
db90b274 | 22 | # define EDDSA_448_PRIVATE_BYTES EDDSA_448_PUBLIC_BYTES |
7324473f | 23 | |
8d55f844 | 24 | /* Number of bytes in an EdDSA private key. */ |
db90b274 MC |
25 | # define EDDSA_448_SIGNATURE_BYTES (EDDSA_448_PUBLIC_BYTES + \ |
26 | EDDSA_448_PRIVATE_BYTES) | |
7324473f | 27 | |
8d55f844 | 28 | /* EdDSA encoding ratio. */ |
db90b274 | 29 | # define C448_EDDSA_ENCODE_RATIO 4 |
7324473f | 30 | |
8d55f844 | 31 | /* EdDSA decoding ratio. */ |
db90b274 | 32 | # define C448_EDDSA_DECODE_RATIO (4 / 4) |
7324473f | 33 | |
8d55f844 MC |
34 | /* |
35 | * EdDSA key generation. This function uses a different (non-Decaf) encoding. | |
7324473f | 36 | * |
8d55f844 MC |
37 | * pubkey (out): The public key. |
38 | * privkey (in): The private key. | |
205fd638 | 39 | */ |
aeeef83c | 40 | c448_error_t c448_ed448_derive_public_key( |
db90b274 MC |
41 | uint8_t pubkey [EDDSA_448_PUBLIC_BYTES], |
42 | const uint8_t privkey [EDDSA_448_PRIVATE_BYTES]); | |
8d55f844 MC |
43 | |
44 | /* | |
45 | * EdDSA signing. | |
46 | * | |
47 | * signature (out): The signature. | |
48 | * privkey (in): The private key. | |
49 | * pubkey (in): The public key. | |
50 | * message (in): The message to sign. | |
51 | * message_len (in): The length of the message. | |
52 | * prehashed (in): Nonzero if the message is actually the hash of something | |
53 | * you want to sign. | |
54 | * context (in): A "context" for this signature of up to 255 bytes. | |
55 | * context_len (in): Length of the context. | |
56 | * | |
57 | * For Ed25519, it is unsafe to use the same key for both prehashed and | |
58 | * non-prehashed messages, at least without some very careful protocol-level | |
59 | * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make | |
60 | * it harder to screw this up, but this C code gives you no seat belt. | |
205fd638 | 61 | */ |
aeeef83c | 62 | c448_error_t c448_ed448_sign( |
db90b274 MC |
63 | uint8_t signature[EDDSA_448_SIGNATURE_BYTES], |
64 | const uint8_t privkey[EDDSA_448_PRIVATE_BYTES], | |
65 | const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES], | |
8d55f844 MC |
66 | const uint8_t *message, size_t message_len, |
67 | uint8_t prehashed, const uint8_t *context, | |
575d5afc | 68 | size_t context_len); |
8d55f844 MC |
69 | |
70 | /* | |
71 | * EdDSA signing with prehash. | |
72 | * | |
73 | * signature (out): The signature. | |
74 | * privkey (in): The private key. | |
75 | * pubkey (in): The public key. | |
76 | * hash (in): The hash of the message. This object will not be modified by the | |
77 | * call. | |
78 | * context (in): A "context" for this signature of up to 255 bytes. Must be the | |
79 | * same as what was used for the prehash. | |
80 | * context_len (in): Length of the context. | |
81 | * | |
82 | * For Ed25519, it is unsafe to use the same key for both prehashed and | |
83 | * non-prehashed messages, at least without some very careful protocol-level | |
84 | * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make | |
85 | * it harder to screw this up, but this C code gives you no seat belt. | |
205fd638 | 86 | */ |
aeeef83c | 87 | c448_error_t c448_ed448_sign_prehash( |
db90b274 MC |
88 | uint8_t signature[EDDSA_448_SIGNATURE_BYTES], |
89 | const uint8_t privkey[EDDSA_448_PRIVATE_BYTES], | |
90 | const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES], | |
8d55f844 MC |
91 | const uint8_t hash[64], |
92 | const uint8_t *context, | |
575d5afc | 93 | size_t context_len); |
8d55f844 MC |
94 | |
95 | /* | |
96 | * EdDSA signature verification. | |
7324473f MC |
97 | * |
98 | * Uses the standard (i.e. less-strict) verification formula. | |
99 | * | |
8d55f844 MC |
100 | * signature (in): The signature. |
101 | * pubkey (in): The public key. | |
102 | * message (in): The message to verify. | |
103 | * message_len (in): The length of the message. | |
104 | * prehashed (in): Nonzero if the message is actually the hash of something you | |
105 | * want to verify. | |
106 | * context (in): A "context" for this signature of up to 255 bytes. | |
107 | * context_len (in): Length of the context. | |
108 | * | |
109 | * For Ed25519, it is unsafe to use the same key for both prehashed and | |
110 | * non-prehashed messages, at least without some very careful protocol-level | |
68b20c00 | 111 | * disambiguation. For Ed448 it is safe. |
7324473f | 112 | */ |
aeeef83c | 113 | c448_error_t c448_ed448_verify(const uint8_t |
db90b274 | 114 | signature[EDDSA_448_SIGNATURE_BYTES], |
205fd638 | 115 | const uint8_t |
db90b274 | 116 | pubkey[EDDSA_448_PUBLIC_BYTES], |
205fd638 MC |
117 | const uint8_t *message, size_t message_len, |
118 | uint8_t prehashed, const uint8_t *context, | |
575d5afc | 119 | uint8_t context_len); |
7324473f | 120 | |
8d55f844 MC |
121 | /* |
122 | * EdDSA signature verification. | |
7324473f MC |
123 | * |
124 | * Uses the standard (i.e. less-strict) verification formula. | |
125 | * | |
8d55f844 MC |
126 | * signature (in): The signature. |
127 | * pubkey (in): The public key. | |
128 | * hash (in): The hash of the message. This object will not be modified by the | |
129 | * call. | |
130 | * context (in): A "context" for this signature of up to 255 bytes. Must be the | |
131 | * same as what was used for the prehash. | |
132 | * context_len (in): Length of the context. | |
133 | * | |
134 | * For Ed25519, it is unsafe to use the same key for both prehashed and | |
135 | * non-prehashed messages, at least without some very careful protocol-level | |
136 | * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make | |
137 | * it harder to screw this up, but this C code gives you no seat belt. | |
7324473f | 138 | */ |
aeeef83c | 139 | c448_error_t c448_ed448_verify_prehash( |
db90b274 MC |
140 | const uint8_t signature[EDDSA_448_SIGNATURE_BYTES], |
141 | const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES], | |
8d55f844 MC |
142 | const uint8_t hash[64], |
143 | const uint8_t *context, | |
575d5afc | 144 | uint8_t context_len); |
8d55f844 MC |
145 | |
146 | /* | |
147 | * EdDSA point encoding. Used internally, exposed externally. | |
db90b274 | 148 | * Multiplies by C448_EDDSA_ENCODE_RATIO first. |
7324473f MC |
149 | * |
150 | * The multiplication is required because the EdDSA encoding represents | |
151 | * the cofactor information, but the Decaf encoding ignores it (which | |
152 | * is the whole point). So if you decode from EdDSA and re-encode to | |
153 | * EdDSA, the cofactor info must get cleared, because the intermediate | |
154 | * representation doesn't track it. | |
155 | * | |
db90b274 MC |
156 | * The way we handle this is to multiply by C448_EDDSA_DECODE_RATIO when |
157 | * decoding, and by C448_EDDSA_ENCODE_RATIO when encoding. The product of | |
aeeef83c MC |
158 | * these ratios is always exactly the cofactor 4, so the cofactor ends up |
159 | * cleared one way or another. But exactly how that shakes out depends on the | |
160 | * base points specified in RFC 8032. | |
7324473f MC |
161 | * |
162 | * The upshot is that if you pass the Decaf/Ristretto base point to | |
db90b274 | 163 | * this function, you will get C448_EDDSA_ENCODE_RATIO times the |
7324473f MC |
164 | * EdDSA base point. |
165 | * | |
8d55f844 MC |
166 | * enc (out): The encoded point. |
167 | * p (in): The point. | |
205fd638 | 168 | */ |
8d55f844 | 169 | void curve448_point_mul_by_ratio_and_encode_like_eddsa( |
db90b274 | 170 | uint8_t enc [EDDSA_448_PUBLIC_BYTES], |
8d55f844 | 171 | const curve448_point_t p); |
7324473f | 172 | |
8d55f844 | 173 | /* |
db90b274 | 174 | * EdDSA point decoding. Multiplies by C448_EDDSA_DECODE_RATIO, and |
8d55f844 | 175 | * ignores cofactor information. |
7324473f | 176 | * |
e7772577 | 177 | * See notes on curve448_point_mul_by_ratio_and_encode_like_eddsa |
7324473f | 178 | * |
8d55f844 MC |
179 | * enc (out): The encoded point. |
180 | * p (in): The point. | |
205fd638 | 181 | */ |
aeeef83c | 182 | c448_error_t curve448_point_decode_like_eddsa_and_mul_by_ratio( |
8d55f844 | 183 | curve448_point_t p, |
db90b274 | 184 | const uint8_t enc[EDDSA_448_PUBLIC_BYTES]); |
8d55f844 | 185 | |
8d55f844 MC |
186 | /* |
187 | * EdDSA to ECDH private key conversion | |
7324473f MC |
188 | * Using the appropriate hash function, hash the EdDSA private key |
189 | * and keep only the lower bytes to get the ECDH private key | |
190 | * | |
8d55f844 MC |
191 | * x (out): The ECDH private key as in RFC7748 |
192 | * ed (in): The EdDSA private key | |
7324473f | 193 | */ |
aeeef83c | 194 | c448_error_t c448_ed448_convert_private_key_to_x448( |
db90b274 MC |
195 | uint8_t x[X448_PRIVATE_BYTES], |
196 | const uint8_t ed[EDDSA_448_PRIVATE_BYTES]); | |
7324473f | 197 | |
68b20c00 | 198 | #endif /* HEADER_ED448_H */ |