_ Git - BoarSSL/blob - Crypto/ECPrivateKey.cs

   1 /*
   2  * Copyright (c) 2017 Thomas Pornin <pornin@bolet.org>
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining
   5  * a copy of this software and associated documentation files (the
   6  * "Software"), to deal in the Software without restriction, including
   7  * without limitation the rights to use, copy, modify, merge, publish,
   8  * distribute, sublicense, and/or sell copies of the Software, and to
   9  * permit persons to whom the Software is furnished to do so, subject to
  10  * the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be
  13  * included in all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  16  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  17  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  18  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  19  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  20  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  21  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22  * SOFTWARE.
  23  */
  24
  25 using System;
  26
  27 namespace Crypto {
  28
  29 /*
  30  * This class contains an EC private key, consisting of two elements:
  31  * -- an elliptic curve
  32  * -- the private integer (X)
  33  *
  34  * The private integer is always handled as an integer modulo the
  35  * curve subbroup order. Its binary representation is unsigned big-endian
  36  * with exactly the same length as the subgroup order.
  37  */
  38
  39 public class ECPrivateKey : IPrivateKey {
  40
  41         public ECCurve Curve {
  42                 get {
  43                         return curve;
  44                 }
  45         }
  46
  47         public byte[] X {
  48                 get {
  49                         return priv;
  50                 }
  51         }
  52
  53         public int KeySizeBits {
  54                 get {
  55                         return BigInt.BitLength(curve.SubgroupOrder);
  56                 }
  57         }
  58
  59         public string AlgorithmName {
  60                 get {
  61                         return "EC";
  62                 }
  63         }
  64
  65         IPublicKey IPrivateKey.PublicKey {
  66                 get {
  67                         return this.PublicKey;
  68                 }
  69         }
  70
  71         public ECPublicKey PublicKey {
  72                 get {
  73                         if (dpk == null) {
  74                                 MutableECPoint G = curve.MakeGenerator();
  75                                 G.MulSpecCT(priv);
  76                                 dpk = new ECPublicKey(curve, G.Encode(false));
  77                         }
  78                         return dpk;
  79                 }
  80         }
  81
  82         ECCurve curve;
  83         byte[] priv;
  84         ECPublicKey dpk;
  85
  86         /*
  87          * Create a new instance with the provided elements. The
  88          * constructor verifies that the provided private integer
  89          * is non-zero and is less than the subgroup order.
  90          */
  91         public ECPrivateKey(ECCurve curve, byte[] X)
  92         {
  93                 this.curve = curve;
  94                 ModInt ms = new ModInt(curve.SubgroupOrder);
  95                 uint good = ms.Decode(X);
  96                 good &= ~ms.IsZeroCT;
  97                 if (good == 0) {
  98                         throw new CryptoException("Invalid private key");
  99                 }
 100                 priv = ms.Encode();
 101                 dpk = null;
 102         }
 103
 104         /*
 105          * CheckValid() runs the validity tests on the curve.
 106          */
 107         public void CheckValid()
 108         {
 109                 curve.CheckValid();
 110         }
 111 }
 112
 113 }