2 * Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright 2015-2016 Cryptography Research, Inc.
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
10 * Originally written by Mike Hamburg
13 #ifndef __C448_ED448_H__
14 # define __C448_ED448_H__ 1
16 # include "point_448.h"
22 /* Number of bytes in an EdDSA public key. */
23 # define EDDSA_448_PUBLIC_BYTES 57
25 /* Number of bytes in an EdDSA private key. */
26 # define EDDSA_448_PRIVATE_BYTES EDDSA_448_PUBLIC_BYTES
28 /* Number of bytes in an EdDSA private key. */
29 # define EDDSA_448_SIGNATURE_BYTES (EDDSA_448_PUBLIC_BYTES + \
30 EDDSA_448_PRIVATE_BYTES)
32 /* EdDSA encoding ratio. */
33 # define C448_EDDSA_ENCODE_RATIO 4
35 /* EdDSA decoding ratio. */
36 # define C448_EDDSA_DECODE_RATIO (4 / 4)
39 * EdDSA key generation. This function uses a different (non-Decaf) encoding.
41 * pubkey (out): The public key.
42 * privkey (in): The private key.
44 c448_error_t c448_ed448_derive_public_key(
45 uint8_t pubkey [EDDSA_448_PUBLIC_BYTES],
46 const uint8_t privkey [EDDSA_448_PRIVATE_BYTES]);
51 * signature (out): The signature.
52 * privkey (in): The private key.
53 * pubkey (in): The public key.
54 * message (in): The message to sign.
55 * message_len (in): The length of the message.
56 * prehashed (in): Nonzero if the message is actually the hash of something
58 * context (in): A "context" for this signature of up to 255 bytes.
59 * context_len (in): Length of the context.
61 * For Ed25519, it is unsafe to use the same key for both prehashed and
62 * non-prehashed messages, at least without some very careful protocol-level
63 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
64 * it harder to screw this up, but this C code gives you no seat belt.
66 c448_error_t c448_ed448_sign(
67 uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
68 const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
69 const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
70 const uint8_t *message, size_t message_len,
71 uint8_t prehashed, const uint8_t *context,
73 __attribute__ ((nonnull(1, 2, 3)));
76 * EdDSA signing with prehash.
78 * signature (out): The signature.
79 * privkey (in): The private key.
80 * pubkey (in): The public key.
81 * hash (in): The hash of the message. This object will not be modified by the
83 * context (in): A "context" for this signature of up to 255 bytes. Must be the
84 * same as what was used for the prehash.
85 * context_len (in): Length of the context.
87 * For Ed25519, it is unsafe to use the same key for both prehashed and
88 * non-prehashed messages, at least without some very careful protocol-level
89 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
90 * it harder to screw this up, but this C code gives you no seat belt.
92 c448_error_t c448_ed448_sign_prehash(
93 uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
94 const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
95 const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
96 const uint8_t hash[64],
97 const uint8_t *context,
99 __attribute__ ((nonnull(1, 2, 3, 4)));
102 * EdDSA signature verification.
104 * Uses the standard (i.e. less-strict) verification formula.
106 * signature (in): The signature.
107 * pubkey (in): The public key.
108 * message (in): The message to verify.
109 * message_len (in): The length of the message.
110 * prehashed (in): Nonzero if the message is actually the hash of something you
112 * context (in): A "context" for this signature of up to 255 bytes.
113 * context_len (in): Length of the context.
115 * For Ed25519, it is unsafe to use the same key for both prehashed and
116 * non-prehashed messages, at least without some very careful protocol-level
117 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
118 * it harder to screw this up, but this C code gives you no seat belt.
120 c448_error_t c448_ed448_verify(const uint8_t
121 signature[EDDSA_448_SIGNATURE_BYTES],
123 pubkey[EDDSA_448_PUBLIC_BYTES],
124 const uint8_t *message, size_t message_len,
125 uint8_t prehashed, const uint8_t *context,
127 __attribute__ ((nonnull(1, 2)));
130 * EdDSA signature verification.
132 * Uses the standard (i.e. less-strict) verification formula.
134 * signature (in): The signature.
135 * pubkey (in): The public key.
136 * hash (in): The hash of the message. This object will not be modified by the
138 * context (in): A "context" for this signature of up to 255 bytes. Must be the
139 * same as what was used for the prehash.
140 * context_len (in): Length of the context.
142 * For Ed25519, it is unsafe to use the same key for both prehashed and
143 * non-prehashed messages, at least without some very careful protocol-level
144 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
145 * it harder to screw this up, but this C code gives you no seat belt.
147 c448_error_t c448_ed448_verify_prehash(
148 const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
149 const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
150 const uint8_t hash[64],
151 const uint8_t *context,
153 __attribute__ ((nonnull(1, 2)));
156 * EdDSA point encoding. Used internally, exposed externally.
157 * Multiplies by C448_EDDSA_ENCODE_RATIO first.
159 * The multiplication is required because the EdDSA encoding represents
160 * the cofactor information, but the Decaf encoding ignores it (which
161 * is the whole point). So if you decode from EdDSA and re-encode to
162 * EdDSA, the cofactor info must get cleared, because the intermediate
163 * representation doesn't track it.
165 * The way we handle this is to multiply by C448_EDDSA_DECODE_RATIO when
166 * decoding, and by C448_EDDSA_ENCODE_RATIO when encoding. The product of
167 * these ratios is always exactly the cofactor 4, so the cofactor ends up
168 * cleared one way or another. But exactly how that shakes out depends on the
169 * base points specified in RFC 8032.
171 * The upshot is that if you pass the Decaf/Ristretto base point to
172 * this function, you will get C448_EDDSA_ENCODE_RATIO times the
175 * enc (out): The encoded point.
178 void curve448_point_mul_by_ratio_and_encode_like_eddsa(
179 uint8_t enc [EDDSA_448_PUBLIC_BYTES],
180 const curve448_point_t p);
183 * EdDSA point decoding. Multiplies by C448_EDDSA_DECODE_RATIO, and
184 * ignores cofactor information.
186 * See notes on curve448_point_mul_by_ratio_and_encode_like_eddsa
188 * enc (out): The encoded point.
191 c448_error_t curve448_point_decode_like_eddsa_and_mul_by_ratio(
193 const uint8_t enc[EDDSA_448_PUBLIC_BYTES]);
196 * EdDSA to ECDH private key conversion
197 * Using the appropriate hash function, hash the EdDSA private key
198 * and keep only the lower bytes to get the ECDH private key
200 * x (out): The ECDH private key as in RFC7748
201 * ed (in): The EdDSA private key
203 c448_error_t c448_ed448_convert_private_key_to_x448(
204 uint8_t x[X448_PRIVATE_BYTES],
205 const uint8_t ed[EDDSA_448_PRIVATE_BYTES]);
211 #endif /* __C448_ED448_H__ */