Index: crypto/p224.h |
diff --git a/crypto/p224.h b/crypto/p224.h |
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+// Copyright (c) 2011 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+#ifndef CRYPTO_P224_H_ |
+#define CRYPTO_P224_H_ |
+#pragma once |
+ |
+#include "base/basictypes.h" |
+ |
+namespace crypto { |
+ |
+// P224 implements an elliptic curve group, commonly known as P224 and defined |
+// in FIPS 186-3, section D.2.2. |
+class P224 { |
+ public: |
+ struct ExternalPoint { |
+ // The external point representation is an (x, y) pair of a point on the |
+ // curve. Each field element is represented as a big-endian number < p. |
+ uint8 affine[2 * 28]; |
+ }; |
+ |
+ // An element of the field (ℤ/pℤ) is represented with 8, 28-bit limbs in |
+ // little endian order. |
+ typedef uint32 FieldElement[8]; |
+ |
+ struct InternalPoint { |
+ // An InternalPoint is represented in Jacobian form (x/z², y/z³). |
+ FieldElement x, y, z; |
+ }; |
+ |
+ // ToInternal converts a point from external to internal representation. It |
+ // verifies that the external point actually lies of the curve and returns |
+ // true if so. |
+ static bool ToInternal(const ExternalPoint& in, InternalPoint* out); |
Wez
2011/11/02 23:46:06
Why is this a member of P224, rather than of P224:
agl
2011/11/03 17:20:49
I'm not sure that I like it, but meh. Have changed
|
+ |
+ // ToExternal converts an internal point to an external point. |
+ static void ToExternal(const InternalPoint& in, ExternalPoint* out); |
Wez
2011/11/02 23:46:06
Similarly here.
agl
2011/11/03 17:20:49
Done.
|
+ |
+ // ScalarMult computes *out = in*scalar where scalar is a big-endian number. |
Wez
2011/11/02 23:46:06
What format is |scalar| in, besides being big-endi
agl
2011/11/03 17:20:49
None. It's just a big-endian number.
Wez
2011/11/03 20:03:46
But it has to be 224 bits == 28 bytes of big-endia
agl
2011/11/04 20:13:22
Oh, I see. Actually no, it could be shorter but si
|
+ static void ScalarMult(const InternalPoint& in, const uint8* scalar, |
+ InternalPoint* out); |
Wez
2011/11/02 23:46:06
According to style, this should be MultiplyByScala
agl
2011/11/03 17:20:49
ScalarMult is a name taken from EBATS: a standard
Wez
2011/11/03 20:03:46
OK, I wondered if that might be the case. I think
|
+ |
+ // ScalarBaseMult computes *out = g*scalar where g is the base point of the |
+ // curve. |
+ static void ScalarBaseMult(const uint8* scalar, InternalPoint* out); |
+ |
+ // Add computes *out = a+b. |
+ static void Add(const InternalPoint& a, const InternalPoint& b, |
+ InternalPoint* out); |
+ |
+ // Negate calculates out = -a; |
+ static void Negate(const InternalPoint& a, InternalPoint* out); |
+}; |
+ |
+} // namespace crypto |
+ |
+#endif // CRYPTO_P224_H_ |