release/src/router/mysql/extra/yassl/taocrypt/src/dh.cpp

   1 /*
   2    Copyright (C) 2000-2007 MySQL AB
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; version 2 of the License.
   7
   8    This program is distributed in the hope that it will be useful,
   9    but WITHOUT ANY WARRANTY; without even the implied warranty of
  10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11    GNU General Public License for more details.
  12
  13    You should have received a copy of the GNU General Public License
  14    along with this program; see the file COPYING. If not, write to the
  15    Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
  16    MA  02110-1301  USA.
  17 */
  18
  19
  20 /* dh.cpp implements Diffie-Hellman support
  21 */
  22
  23 #include "runtime.hpp"
  24 #include "dh.hpp"
  25 #include "asn.hpp"
  26 #include <math.h>
  27
  28 namespace TaoCrypt {
  29
  30
  31 namespace {  // locals
  32
  33 unsigned int DiscreteLogWorkFactor(unsigned int n)
  34 {
  35     // assuming discrete log takes about the same time as factoring
  36     if (n<5)
  37         return 0;
  38     else
  39         return (unsigned int)(2.4 * pow((double)n, 1.0/3.0) *
  40                 pow(log(double(n)), 2.0/3.0) - 5);
  41 }
  42
  43 } // namespace locals
  44
  45
  46 // Generate a DH Key Pair
  47 void DH::GenerateKeyPair(RandomNumberGenerator& rng, byte* priv, byte* pub)
  48 {
  49     GeneratePrivate(rng, priv);
  50     GeneratePublic(priv, pub);
  51 }
  52
  53
  54 // Generate private value
  55 void DH::GeneratePrivate(RandomNumberGenerator& rng, byte* priv)
  56 {
  57     Integer x(rng, Integer::One(), min(p_ - 1,
  58         Integer::Power2(2*DiscreteLogWorkFactor(p_.BitCount())) ) );
  59     x.Encode(priv, p_.ByteCount());
  60 }
  61
  62
  63 // Generate public value
  64 void DH::GeneratePublic(const byte* priv, byte* pub)
  65 {
  66     const word32 bc(p_.ByteCount());
  67     Integer x(priv, bc);
  68     Integer y(a_exp_b_mod_c(g_, x, p_));
  69     y.Encode(pub, bc);
  70 }
  71
  72
  73 // Generate Agreement
  74 void DH::Agree(byte* agree, const byte* priv, const byte* otherPub, word32
  75                otherSz)
  76 {
  77     const word32 bc(p_.ByteCount());
  78     Integer x(priv, bc);
  79     Integer y;
  80     if (otherSz)
  81         y.Decode(otherPub, otherSz);
  82     else
  83         y.Decode(otherPub, bc);
  84
  85     Integer z(a_exp_b_mod_c(y, x, p_));
  86     z.Encode(agree, bc);
  87 }
  88
  89
  90 DH::DH(Source& source)
  91 {
  92     Initialize(source);
  93 }
  94
  95
  96 void DH::Initialize(Source& source)
  97 {
  98     DH_Decoder decoder(source);
  99     decoder.Decode(*this);
 100 }
 101
 102
 103 } // namespace