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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 #ifndef CRYPTO_CURVE25519_H | |
6 #define CRYPTO_CURVE25519_H | |
7 | |
8 #include <stddef.h> | |
9 #include <stdint.h> | |
10 | |
11 #include "crypto/crypto_export.h" | |
12 | |
13 namespace crypto { | |
14 | |
15 // Curve25519 implements the elliptic curve group known as Curve25519, as | |
16 // described in "Curve 25519: new Diffie-Hellman Speed Records", | |
17 // by D.J. Bernstein. Additional information is available at | |
18 // http://cr.yp.to/ecdh.html. | |
19 // | |
20 // TODO(davidben): Once iOS is switched to BoringSSL (https://crbug.com/338886), | |
21 // remove this file altogether and switch callers to using BoringSSL's | |
22 // curve25519.h directly. | |
23 namespace curve25519 { | |
24 | |
25 // kBytes is the number of bytes in the result of the Diffie-Hellman operation, | |
26 // which is an element of GF(2^255-19). | |
27 static const size_t kBytes = 32; | |
28 | |
29 // kScalarBytes is the number of bytes in an element of the scalar field: | |
30 // GF(2^252 + 27742317777372353535851937790883648493). | |
31 static const size_t kScalarBytes = 32; | |
32 | |
33 // ScalarMult computes the |shared_key| from |private_key| and | |
34 // |peer_public_key|. This method is a wrapper for |curve25519_donna()|. It | |
35 // calls that function with |private_key| as |secret| and |peer_public_key| as | |
36 // basepoint. |private_key| should be of length |kScalarBytes| and | |
37 // |peer_public_key| should be of length |kBytes|. It returns true on success | |
38 // and false if |peer_public_key| was invalid. | |
39 // See the "Computing shared secrets" section of http://cr.yp.to/ecdh.html. | |
40 CRYPTO_EXPORT bool ScalarMult(const uint8_t* private_key, | |
41 const uint8_t* peer_public_key, | |
42 uint8_t* shared_key); | |
43 | |
44 // ScalarBaseMult computes the |public_key| from |private_key|. This method is a | |
45 // wrapper for |curve25519_donna()|. It calls that function with |private_key| | |
46 // as |secret| and |kBasePoint| as basepoint. |private_key| should be of length | |
47 // |kScalarBytes|. See "Computing public keys" section of | |
48 // http://cr.yp.to/ecdh.html. | |
49 CRYPTO_EXPORT void ScalarBaseMult(const uint8_t* private_key, | |
50 uint8_t* public_key); | |
51 | |
52 } // namespace curve25519 | |
53 | |
54 } // namespace crypto | |
55 | |
56 #endif // CRYPTO_CURVE25519_H | |
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