crypto/ec/curve448/ed448.h

   1 /*
   2  * Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.
   3  * Copyright 2015-2016 Cryptography Research, Inc.
   4  *
   5  * Licensed under the Apache License 2.0 (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
  13 #ifndef OSSL_CRYPTO_EC_CURVE448_ED448_H
  14 # define OSSL_CRYPTO_EC_CURVE448_ED448_H
  15
  16 # include "point_448.h"
  17
  18 /* Number of bytes in an EdDSA public key. */
  19 # define EDDSA_448_PUBLIC_BYTES 57
  20
  21 /* Number of bytes in an EdDSA private key. */
  22 # define EDDSA_448_PRIVATE_BYTES EDDSA_448_PUBLIC_BYTES
  23
  24 /* Number of bytes in an EdDSA private key. */
  25 # define EDDSA_448_SIGNATURE_BYTES (EDDSA_448_PUBLIC_BYTES + \
  26                                     EDDSA_448_PRIVATE_BYTES)
  27
  28 /* EdDSA encoding ratio. */
  29 # define C448_EDDSA_ENCODE_RATIO 4
  30
  31 /* EdDSA decoding ratio. */
  32 # define C448_EDDSA_DECODE_RATIO (4 / 4)
  33
  34 /*
  35  * EdDSA key generation.  This function uses a different (non-Decaf) encoding.
  36  *
  37  * pubkey (out): The public key.
  38  * privkey (in): The private key.
  39  */
  40 c448_error_t
  41 ossl_c448_ed448_derive_public_key(
  42                               OSSL_LIB_CTX *ctx,
  43                               uint8_t pubkey [EDDSA_448_PUBLIC_BYTES],
  44                               const uint8_t privkey [EDDSA_448_PRIVATE_BYTES],
  45                               const char *propq);
  46
  47 /*
  48  * EdDSA signing.
  49  *
  50  * signature (out): The signature.
  51  * privkey (in): The private key.
  52  * pubkey (in):  The public key.
  53  * message (in):  The message to sign.
  54  * message_len (in):  The length of the message.
  55  * prehashed (in):  Nonzero if the message is actually the hash of something
  56  *                  you want to sign.
  57  * context (in):  A "context" for this signature of up to 255 bytes.
  58  * context_len (in):  Length of the context.
  59  *
  60  * For Ed25519, it is unsafe to use the same key for both prehashed and
  61  * non-prehashed messages, at least without some very careful protocol-level
  62  * disambiguation.  For Ed448 it is safe.
  63  */
  64 c448_error_t
  65 ossl_c448_ed448_sign(OSSL_LIB_CTX *ctx,
  66                      uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
  67                      const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
  68                      const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
  69                      const uint8_t *message, size_t message_len,
  70                      uint8_t prehashed, const uint8_t *context,
  71                      size_t context_len,
  72                      const char *propq);
  73
  74 /*
  75  * EdDSA signing with prehash.
  76  *
  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
  81  *            call.
  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.
  85  *
  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.
  89  */
  90 c448_error_t
  91 ossl_c448_ed448_sign_prehash(OSSL_LIB_CTX *ctx,
  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,
  97                              size_t context_len,
  98                              const char *propq);
  99
 100 /*
 101  * EdDSA signature verification.
 102  *
 103  * Uses the standard (i.e. less-strict) verification formula.
 104  *
 105  * signature (in): The signature.
 106  * pubkey (in): The public key.
 107  * message (in): The message to verify.
 108  * message_len (in): The length of the message.
 109  * prehashed (in): Nonzero if the message is actually the hash of something you
 110  *                 want to verify.
 111  * context (in): A "context" for this signature of up to 255 bytes.
 112  * context_len (in): Length of the context.
 113  *
 114  * For Ed25519, it is unsafe to use the same key for both prehashed and
 115  * non-prehashed messages, at least without some very careful protocol-level
 116  * disambiguation.  For Ed448 it is safe.
 117  */
 118 c448_error_t
 119 ossl_c448_ed448_verify(OSSL_LIB_CTX *ctx,
 120                        const uint8_t
 121                        signature[EDDSA_448_SIGNATURE_BYTES],
 122                        const uint8_t
 123                        pubkey[EDDSA_448_PUBLIC_BYTES],
 124                        const uint8_t *message, size_t message_len,
 125                        uint8_t prehashed, const uint8_t *context,
 126                        uint8_t context_len,
 127                        const char *propq);
 128
 129 /*
 130  * EdDSA signature verification.
 131  *
 132  * Uses the standard (i.e. less-strict) verification formula.
 133  *
 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
 137  *            call.
 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.
 141  *
 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.
 145  */
 146 c448_error_t
 147 ossl_c448_ed448_verify_prehash(
 148                             OSSL_LIB_CTX *ctx,
 149                             const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
 150                             const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
 151                             const uint8_t hash[64],
 152                             const uint8_t *context,
 153                             uint8_t context_len,
 154                             const char *propq);
 155
 156 /*
 157  * EdDSA point encoding.  Used internally, exposed externally.
 158  * Multiplies by C448_EDDSA_ENCODE_RATIO first.
 159  *
 160  * The multiplication is required because the EdDSA encoding represents
 161  * the cofactor information, but the Decaf encoding ignores it (which
 162  * is the whole point).  So if you decode from EdDSA and re-encode to
 163  * EdDSA, the cofactor info must get cleared, because the intermediate
 164  * representation doesn't track it.
 165  *
 166  * The way we handle this is to multiply by C448_EDDSA_DECODE_RATIO when
 167  * decoding, and by C448_EDDSA_ENCODE_RATIO when encoding.  The product of
 168  * these ratios is always exactly the cofactor 4, so the cofactor ends up
 169  * cleared one way or another.  But exactly how that shakes out depends on the
 170  * base points specified in RFC 8032.
 171  *
 172  * The upshot is that if you pass the Decaf/Ristretto base point to
 173  * this function, you will get C448_EDDSA_ENCODE_RATIO times the
 174  * EdDSA base point.
 175  *
 176  * enc (out): The encoded point.
 177  * p (in): The point.
 178  */
 179 void
 180 ossl_curve448_point_mul_by_ratio_and_encode_like_eddsa(
 181                                     uint8_t enc [EDDSA_448_PUBLIC_BYTES],
 182                                     const curve448_point_t p);
 183
 184 /*
 185  * EdDSA point decoding.  Multiplies by C448_EDDSA_DECODE_RATIO, and
 186  * ignores cofactor information.
 187  *
 188  * See notes on curve448_point_mul_by_ratio_and_encode_like_eddsa
 189  *
 190  * enc (out): The encoded point.
 191  * p (in): The point.
 192  */
 193 c448_error_t
 194 ossl_curve448_point_decode_like_eddsa_and_mul_by_ratio(
 195                             curve448_point_t p,
 196                             const uint8_t enc[EDDSA_448_PUBLIC_BYTES]);
 197
 198 /*
 199  * EdDSA to ECDH private key conversion
 200  * Using the appropriate hash function, hash the EdDSA private key
 201  * and keep only the lower bytes to get the ECDH private key
 202  *
 203  * x (out): The ECDH private key as in RFC7748
 204  * ed (in): The EdDSA private key
 205  */
 206 c448_error_t
 207 ossl_c448_ed448_convert_private_key_to_x448(
 208                                     OSSL_LIB_CTX *ctx,
 209                                     uint8_t x[X448_PRIVATE_BYTES],
 210                                     const uint8_t ed[EDDSA_448_PRIVATE_BYTES],
 211                                     const char *propq);
 212
 213 #endif                          /* OSSL_CRYPTO_EC_CURVE448_ED448_H */