crypto/ec/curve448/ed448.h

   1 /*
   2  * Copyright 2017-2018 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 c448_ed448_derive_public_key(
  41                         OPENSSL_CTX *ctx,
  42                         uint8_t pubkey [EDDSA_448_PUBLIC_BYTES],
  43                         const uint8_t privkey [EDDSA_448_PRIVATE_BYTES]);
  44
  45 /*
  46  * EdDSA signing.
  47  *
  48  * signature (out): The signature.
  49  * privkey (in): The private key.
  50  * pubkey (in):  The public key.
  51  * message (in):  The message to sign.
  52  * message_len (in):  The length of the message.
  53  * prehashed (in):  Nonzero if the message is actually the hash of something
  54  *                  you want to sign.
  55  * context (in):  A "context" for this signature of up to 255 bytes.
  56  * context_len (in):  Length of the context.
  57  *
  58  * For Ed25519, it is unsafe to use the same key for both prehashed and
  59  * non-prehashed messages, at least without some very careful protocol-level
  60  * disambiguation.  For Ed448 it is safe.
  61  */
  62 c448_error_t c448_ed448_sign(
  63                         OPENSSL_CTX *ctx,
  64                         uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
  65                         const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
  66                         const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
  67                         const uint8_t *message, size_t message_len,
  68                         uint8_t prehashed, const uint8_t *context,
  69                         size_t context_len);
  70
  71 /*
  72  * EdDSA signing with prehash.
  73  *
  74  * signature (out): The signature.
  75  * privkey (in): The private key.
  76  * pubkey (in): The public key.
  77  * hash (in): The hash of the message.  This object will not be modified by the
  78  *            call.
  79  * context (in): A "context" for this signature of up to 255 bytes.  Must be the
  80  *               same as what was used for the prehash.
  81  * context_len (in): Length of the context.
  82  *
  83  * For Ed25519, it is unsafe to use the same key for both prehashed and
  84  * non-prehashed messages, at least without some very careful protocol-level
  85  * disambiguation.  For Ed448 it is safe.
  86  */
  87 c448_error_t c448_ed448_sign_prehash(
  88                         OPENSSL_CTX *ctx,
  89                         uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
  90                         const uint8_t privkey[EDDSA_448_PRIVATE_BYTES],
  91                         const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
  92                         const uint8_t hash[64],
  93                         const uint8_t *context,
  94                         size_t context_len);
  95
  96 /*
  97  * EdDSA signature verification.
  98  *
  99  * Uses the standard (i.e. less-strict) verification formula.
 100  *
 101  * signature (in): The signature.
 102  * pubkey (in): The public key.
 103  * message (in): The message to verify.
 104  * message_len (in): The length of the message.
 105  * prehashed (in): Nonzero if the message is actually the hash of something you
 106  *                 want to verify.
 107  * context (in): A "context" for this signature of up to 255 bytes.
 108  * context_len (in): Length of the context.
 109  *
 110  * For Ed25519, it is unsafe to use the same key for both prehashed and
 111  * non-prehashed messages, at least without some very careful protocol-level
 112  * disambiguation.  For Ed448 it is safe.
 113  */
 114 c448_error_t c448_ed448_verify(OPENSSL_CTX *ctx,
 115                                const uint8_t
 116                                signature[EDDSA_448_SIGNATURE_BYTES],
 117                                const uint8_t
 118                                pubkey[EDDSA_448_PUBLIC_BYTES],
 119                                const uint8_t *message, size_t message_len,
 120                                uint8_t prehashed, const uint8_t *context,
 121                                uint8_t context_len);
 122
 123 /*
 124  * EdDSA signature verification.
 125  *
 126  * Uses the standard (i.e. less-strict) verification formula.
 127  *
 128  * signature (in): The signature.
 129  * pubkey (in): The public key.
 130  * hash (in): The hash of the message.  This object will not be modified by the
 131  *            call.
 132  * context (in): A "context" for this signature of up to 255 bytes.  Must be the
 133  *               same as what was used for the prehash.
 134  * context_len (in): Length of the context.
 135  *
 136  * For Ed25519, it is unsafe to use the same key for both prehashed and
 137  * non-prehashed messages, at least without some very careful protocol-level
 138  * disambiguation.  For Ed448 it is safe.
 139  */
 140 c448_error_t c448_ed448_verify_prehash(
 141                     OPENSSL_CTX *ctx,
 142                     const uint8_t signature[EDDSA_448_SIGNATURE_BYTES],
 143                     const uint8_t pubkey[EDDSA_448_PUBLIC_BYTES],
 144                     const uint8_t hash[64],
 145                     const uint8_t *context,
 146                     uint8_t context_len);
 147
 148 /*
 149  * EdDSA point encoding.  Used internally, exposed externally.
 150  * Multiplies by C448_EDDSA_ENCODE_RATIO first.
 151  *
 152  * The multiplication is required because the EdDSA encoding represents
 153  * the cofactor information, but the Decaf encoding ignores it (which
 154  * is the whole point).  So if you decode from EdDSA and re-encode to
 155  * EdDSA, the cofactor info must get cleared, because the intermediate
 156  * representation doesn't track it.
 157  *
 158  * The way we handle this is to multiply by C448_EDDSA_DECODE_RATIO when
 159  * decoding, and by C448_EDDSA_ENCODE_RATIO when encoding.  The product of
 160  * these ratios is always exactly the cofactor 4, so the cofactor ends up
 161  * cleared one way or another.  But exactly how that shakes out depends on the
 162  * base points specified in RFC 8032.
 163  *
 164  * The upshot is that if you pass the Decaf/Ristretto base point to
 165  * this function, you will get C448_EDDSA_ENCODE_RATIO times the
 166  * EdDSA base point.
 167  *
 168  * enc (out): The encoded point.
 169  * p (in): The point.
 170  */
 171 void curve448_point_mul_by_ratio_and_encode_like_eddsa(
 172                                     uint8_t enc [EDDSA_448_PUBLIC_BYTES],
 173                                     const curve448_point_t p);
 174
 175 /*
 176  * EdDSA point decoding.  Multiplies by C448_EDDSA_DECODE_RATIO, and
 177  * ignores cofactor information.
 178  *
 179  * See notes on curve448_point_mul_by_ratio_and_encode_like_eddsa
 180  *
 181  * enc (out): The encoded point.
 182  * p (in): The point.
 183  */
 184 c448_error_t curve448_point_decode_like_eddsa_and_mul_by_ratio(
 185                             curve448_point_t p,
 186                             const uint8_t enc[EDDSA_448_PUBLIC_BYTES]);
 187
 188 /*
 189  * EdDSA to ECDH private key conversion
 190  * Using the appropriate hash function, hash the EdDSA private key
 191  * and keep only the lower bytes to get the ECDH private key
 192  *
 193  * x (out): The ECDH private key as in RFC7748
 194  * ed (in): The EdDSA private key
 195  */
 196 c448_error_t c448_ed448_convert_private_key_to_x448(
 197                             OPENSSL_CTX *ctx,
 198                             uint8_t x[X448_PRIVATE_BYTES],
 199                             const uint8_t ed[EDDSA_448_PRIVATE_BYTES]);
 200
 201 #endif                          /* OSSL_CRYPTO_EC_CURVE448_ED448_H */