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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 #include <stdint.h> | |
8 | |
9 #include "crypto/secure_util.h" | |
10 | |
11 // Curve25519 is specified in terms of byte strings, not numbers, so all | |
12 // implementations take and return the same sequence of bits. So the byte | |
13 // order is implicitly specified as in, say, SHA1. | |
14 // | |
15 // Prototype for |curve25519_donna| function in | |
16 // third_party/curve25519-donna/curve25519-donna.c | |
17 extern "C" int curve25519_donna(uint8_t*, const uint8_t*, const uint8_t*); | |
18 | |
19 namespace crypto { | |
20 | |
21 namespace curve25519 { | |
22 | |
23 bool ScalarMult(const uint8_t* private_key, | |
24 const uint8_t* peer_public_key, | |
25 uint8_t* shared_key) { | |
26 curve25519_donna(shared_key, private_key, peer_public_key); | |
27 | |
28 // The all-zero output results when the input is a point of small order. | |
29 static const uint8_t kZeros[32] = {0}; | |
30 return !SecureMemEqual(shared_key, kZeros, 32); | |
31 } | |
32 | |
33 // kBasePoint is the base point (generator) of the elliptic curve group. | |
34 // It is little-endian version of '9' followed by 31 zeros. | |
35 // See "Computing public keys" section of http://cr.yp.to/ecdh.html. | |
36 static const uint8_t kBasePoint[32] = {9}; | |
37 | |
38 void ScalarBaseMult(const uint8_t* private_key, uint8_t* public_key) { | |
39 curve25519_donna(public_key, private_key, kBasePoint); | |
40 } | |
41 | |
42 } // namespace curve25519 | |
43 | |
44 } // namespace crypto | |
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