_ Git - BoarSSL/blob - Crypto/ECPublicKey.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 public key, consisting of two elements:
  31  * -- an elliptic curve
  32  * -- a non-zero point on that curve (called "Pub")
  33  */
  34
  35 public class ECPublicKey : IPublicKey {
  36
  37         public ECCurve Curve {
  38                 get {
  39                         return curve;
  40                 }
  41         }
  42
  43         public byte[] Pub {
  44                 get {
  45                         return pub;
  46                 }
  47         }
  48
  49         public int KeySizeBits {
  50                 get {
  51                         return BigInt.BitLength(curve.SubgroupOrder);
  52                 }
  53         }
  54
  55         public string AlgorithmName {
  56                 get {
  57                         return "EC";
  58                 }
  59         }
  60
  61         ECCurve curve;
  62         byte[] pub;
  63         int hashCode;
  64
  65         internal MutableECPoint iPub;
  66
  67         /*
  68          * Create a new instance with the provided elements. The
  69          * constructor verifies that the provided point is part of
  70          * the curve.
  71          */
  72         public ECPublicKey(ECCurve curve, byte[] Pub)
  73         {
  74                 this.curve = curve;
  75                 this.pub = Pub;
  76                 iPub = curve.Decode(Pub);
  77                 if (iPub.IsInfinity) {
  78                         throw new CryptoException(
  79                                 "Public key point is infinity");
  80                 }
  81                 hashCode = curve.GetHashCode()
  82                         ^ (int)BigInt.HashInt(iPub.X)
  83                         ^ (int)BigInt.HashInt(iPub.Y);
  84         }
  85
  86         /*
  87          * CheckValid() runs the validity tests on the curve, and
  88          * verifies that provided point is part of a subgroup with
  89          * the advertised subgroup order.
  90          */
  91         public void CheckValid()
  92         {
  93                 curve.CheckValid();
  94                 MutableECPoint P = iPub.Dup();
  95                 if (P.MulSpecCT(curve.SubgroupOrder) == 0
  96                         || !P.IsInfinity)
  97                 {
  98                         throw new CryptoException(
  99                                 "Public key point not on the defined subgroup");
 100                 }
 101         }
 102
 103         public override bool Equals(object obj)
 104         {
 105                 ECPublicKey pk = obj as ECPublicKey;
 106                 if (pk == null) {
 107                         return false;
 108                 }
 109                 if (hashCode != pk.hashCode) {
 110                         return false;
 111                 }
 112                 return iPub.Eq(pk.iPub);
 113         }
 114
 115         public override int GetHashCode()
 116         {
 117                 return hashCode;
 118         }
 119 }
 120
 121 }