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,
75 * EdDSA signing with prehash.
77 * signature (out): The signature.
78 * privkey (in): The private key.
79 * pubkey (in): The public key.
80 * hash (in): The hash of the message. This object will not be modified by the
82 * context (in): A "context" for this signature of up to 255 bytes. Must be the
83 * same as what was used for the prehash.
84 * context_len (in): Length of the context.
86 * For Ed25519, it is unsafe to use the same key for both prehashed and
87 * non-prehashed messages, at least without some very careful protocol-level
88 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
89 * it harder to screw this up, but this C code gives you no seat belt.
91 c448_error_t c448_ed448_sign_prehash(
92 uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
93 const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
94 const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
95 const uint8_t hash[64],
96 const uint8_t *context,
100 * EdDSA signature verification.
102 * Uses the standard (i.e. less-strict) verification formula.
104 * signature (in): The signature.
105 * pubkey (in): The public key.
106 * message (in): The message to verify.
107 * message_len (in): The length of the message.
108 * prehashed (in): Nonzero if the message is actually the hash of something you
110 * context (in): A "context" for this signature of up to 255 bytes.
111 * context_len (in): Length of the context.
113 * For Ed25519, it is unsafe to use the same key for both prehashed and
114 * non-prehashed messages, at least without some very careful protocol-level
115 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
116 * it harder to screw this up, but this C code gives you no seat belt.
118 c448_error_t c448_ed448_verify(const uint8_t
119 signature[EDDSA_448_SIGNATURE_BYTES],
121 pubkey[EDDSA_448_PUBLIC_BYTES],
122 const uint8_t *message, size_t message_len,
123 uint8_t prehashed, const uint8_t *context,
124 uint8_t context_len);
127 * EdDSA signature verification.
129 * Uses the standard (i.e. less-strict) verification formula.
131 * signature (in): The signature.
132 * pubkey (in): The public key.
133 * hash (in): The hash of the message. This object will not be modified by the
135 * context (in): A "context" for this signature of up to 255 bytes. Must be the
136 * same as what was used for the prehash.
137 * context_len (in): Length of the context.
139 * For Ed25519, it is unsafe to use the same key for both prehashed and
140 * non-prehashed messages, at least without some very careful protocol-level
141 * disambiguation. For Ed448 it is safe. The C++ wrapper is designed to make
142 * it harder to screw this up, but this C code gives you no seat belt.
144 c448_error_t c448_ed448_verify_prehash(
145 const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
146 const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
147 const uint8_t hash[64],
148 const uint8_t *context,
149 uint8_t context_len);
152 * EdDSA point encoding. Used internally, exposed externally.
153 * Multiplies by C448_EDDSA_ENCODE_RATIO first.
155 * The multiplication is required because the EdDSA encoding represents
156 * the cofactor information, but the Decaf encoding ignores it (which
157 * is the whole point). So if you decode from EdDSA and re-encode to
158 * EdDSA, the cofactor info must get cleared, because the intermediate
159 * representation doesn't track it.
161 * The way we handle this is to multiply by C448_EDDSA_DECODE_RATIO when
162 * decoding, and by C448_EDDSA_ENCODE_RATIO when encoding. The product of
163 * these ratios is always exactly the cofactor 4, so the cofactor ends up
164 * cleared one way or another. But exactly how that shakes out depends on the
165 * base points specified in RFC 8032.
167 * The upshot is that if you pass the Decaf/Ristretto base point to
168 * this function, you will get C448_EDDSA_ENCODE_RATIO times the
171 * enc (out): The encoded point.
174 void curve448_point_mul_by_ratio_and_encode_like_eddsa(
175 uint8_t enc [EDDSA_448_PUBLIC_BYTES],
176 const curve448_point_t p);
179 * EdDSA point decoding. Multiplies by C448_EDDSA_DECODE_RATIO, and
180 * ignores cofactor information.
182 * See notes on curve448_point_mul_by_ratio_and_encode_like_eddsa
184 * enc (out): The encoded point.
187 c448_error_t curve448_point_decode_like_eddsa_and_mul_by_ratio(
189 const uint8_t enc[EDDSA_448_PUBLIC_BYTES]);
192 * EdDSA to ECDH private key conversion
193 * Using the appropriate hash function, hash the EdDSA private key
194 * and keep only the lower bytes to get the ECDH private key
196 * x (out): The ECDH private key as in RFC7748
197 * ed (in): The EdDSA private key
199 c448_error_t c448_ed448_convert_private_key_to_x448(
200 uint8_t x[X448_PRIVATE_BYTES],
201 const uint8_t ed[EDDSA_448_PRIVATE_BYTES]);
207 #endif /* __C448_ED448_H__ */