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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // This is an implementation of the P224 elliptic curve group. It's written to | 5 // This is an implementation of the P224 elliptic curve group. It's written to |
6 // be short and simple rather than fast, although it's still constant-time. | 6 // be short and simple rather than fast, although it's still constant-time. |
7 // | 7 // |
8 // See http://www.imperialviolet.org/2010/12/04/ecc.html ([1]) for background. | 8 // See http://www.imperialviolet.org/2010/12/04/ecc.html ([1]) for background. |
9 | 9 |
10 #include "crypto/p224.h" | 10 #include "crypto/p224.h" |
11 | 11 |
12 #include <string.h> | 12 #include <string.h> |
13 | 13 |
14 #include "base/sys_byteorder.h" | 14 #include "base/sys_byteorder.h" |
15 | 15 |
| 16 #if defined(OS_WIN) |
| 17 // Allow htonl/ntohl to be called without requiring ws2_32.dll to be loaded, |
| 18 // which isn't available in Chrome's sandbox. See crbug.com/116591. |
| 19 // TODO(wez): Replace these calls with base::htonl() etc when available. |
| 20 #define ntohl(x) _byteswap_ulong(x) |
| 21 #define htonl(x) _byteswap_ulong(x) |
| 22 #endif // OS_WIN |
| 23 |
16 namespace { | 24 namespace { |
17 | 25 |
18 // Field element functions. | 26 // Field element functions. |
19 // | 27 // |
20 // The field that we're dealing with is ℤ/pℤ where p = 2**224 - 2**96 + 1. | 28 // The field that we're dealing with is ℤ/pℤ where p = 2**224 - 2**96 + 1. |
21 // | 29 // |
22 // Field elements are represented by a FieldElement, which is a typedef to an | 30 // Field elements are represented by a FieldElement, which is a typedef to an |
23 // array of 8 uint32's. The value of a FieldElement, a, is: | 31 // array of 8 uint32's. The value of a FieldElement, a, is: |
24 // a[0] + 2**28·a[1] + 2**56·a[1] + ... + 2**196·a[7] | 32 // a[0] + 2**28·a[1] + 2**56·a[1] + ... + 2**196·a[7] |
25 // | 33 // |
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669 Subtract(&out->y, kP, y); | 677 Subtract(&out->y, kP, y); |
670 Reduce(&out->y); | 678 Reduce(&out->y); |
671 | 679 |
672 memset(&out->z, 0, sizeof(out->z)); | 680 memset(&out->z, 0, sizeof(out->z)); |
673 out->z[0] = 1; | 681 out->z[0] = 1; |
674 } | 682 } |
675 | 683 |
676 } // namespace p224 | 684 } // namespace p224 |
677 | 685 |
678 } // namespace crypto | 686 } // namespace crypto |
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