crypto/curve25519.h

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CRYPTO_CURVE25519_H
   6 #define CRYPTO_CURVE25519_H
   7
   8 #include "base/basictypes.h"
   9 #include "crypto/crypto_export.h"
  10
  11 namespace crypto {
  12
  13 // Curve25519 implements the elliptic curve group known as Curve25519, as
  14 // described in "Curve 25519: new Diffie-Hellman Speed Records",
  15 // by D.J. Bernstein. Additional information is available at
  16 // http://cr.yp.to/ecdh.html.
  17 namespace curve25519 {
  18
  19 // kBytes is the number of bytes in the result of the Diffie-Hellman operation,
  20 // which is an element of GF(2^255-19).
  21 static const size_t kBytes = 32;
  22
  23 // kScalarBytes is the number of bytes in an element of the scalar field:
  24 // GF(2^252 + 27742317777372353535851937790883648493).
  25 static const size_t kScalarBytes = 32;
  26
  27 // ScalarMult computes the |shared_key| from |private_key| and
  28 // |peer_public_key|. This method is a wrapper for |curve25519_donna()|. It
  29 // calls that function with |private_key| as |secret| and |peer_public_key| as
  30 // basepoint. |private_key| should be of length |kScalarBytes| and
  31 // |peer_public_key| should be of length |kBytes|.
  32 // See "Computing shared secrets" section of/ http://cr.yp.to/ecdh.html.
  33 CRYPTO_EXPORT void ScalarMult(const uint8* private_key,
  34                               const uint8* peer_public_key,
  35                               uint8* shared_key);
  36
  37 // ScalarBaseMult computes the |public_key| from |private_key|. This method is a
  38 // wrapper for |curve25519_donna()|. It calls that function with |private_key|
  39 // as |secret| and |kBasePoint| as basepoint. |private_key| should be of length
  40 // |kScalarBytes|. See "Computing public keys" section of
  41 // http://cr.yp.to/ecdh.html.
  42 CRYPTO_EXPORT void ScalarBaseMult(const uint8* private_key, uint8* public_key);
  43
  44 }  // namespace curve25519
  45
  46 }  // namespace crypto
  47
  48 #endif  // CRYPTO_CURVE25519_H