crypto/curve25519.cc

   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 #include "crypto/curve25519.h"
   6
   7 // Curve25519 is specified in terms of byte strings, not numbers, so all
   8 // implementations take and return the same sequence of bits. So the byte
   9 // order is implicitly specified as in, say, SHA1.
  10 //
  11 // Prototype for |curve25519_donna| function in
  12 // third_party/curve25519-donna/curve25519-donna.c
  13 extern "C" int curve25519_donna(uint8*, const uint8*, const uint8*);
  14
  15 namespace crypto {
  16
  17 namespace curve25519 {
  18
  19 void ScalarMult(const uint8* private_key,
  20                 const uint8* peer_public_key,
  21                 uint8* shared_key) {
  22   curve25519_donna(shared_key, private_key, peer_public_key);
  23 }
  24
  25 // kBasePoint is the base point (generator) of the elliptic curve group.
  26 // It is little-endian version of '9' followed by 31 zeros.
  27 // See "Computing public keys" section of http://cr.yp.to/ecdh.html.
  28 static const unsigned char kBasePoint[32] = {9};
  29
  30 void ScalarBaseMult(const uint8* private_key, uint8* public_key) {
  31   curve25519_donna(public_key, private_key, kBasePoint);
  32 }
  33
  34 }  // namespace curve25519
  35
  36 }  // namespace crypto