Re: Diffie-Hellman Coding

[James Lee]

hi Wei Dai,

i might use the wrong way to examine the variables. i just use "cout" to 
show the variables. fyi, i used Crypto++ 4.2 on Windows 2000, MS Visual C++ 
(MS Visual Studio).
the output below (it might shows different from what i sent), is based of 
the fixed seed. both PrivateKeys are empty and the Agreed Values are not 
identical.
attached the coding.

thank you very much.

---------------------Output---------------------------------------------
acPrivateKeyA:
acPublicKeyA: �gⁿg/�w��≡─╛�↨[
acPrivateKeyB:
acPublicKeyB: ���S↑�Xδ����╪◄�╛
acAgreedValueA: 
xV/4y�G∩sN╙�4�╩����S↑�Xδ����╪◄�╛
acAgreedValueB: 
xV/4y�G∩sN╙�4�╩�xV/4y�G∩sN╙�4�╩����S↑�Xδ����╪◄�╛

---------------------Code-----------------------------------------------
#include "randpool.h"
#include "dh.h"
#include <iostream>
USING_NAMESPACE(CryptoPP)
USING_NAMESPACE(std)
void main () {

// Alice
// Create auto seeded random number generator
// CryptoPP::AutoSeededRandomPool autorng = 
CryptoPP::AutoSeededRandomPool();

char* Seed = "seed";
RandomPool randPool;
randPool.Put((byte *)Seed, strlen((char*)Seed));
// Create diffie hellman class
CryptoPP::DH dhDHA = CryptoPP::DH(randPool, 128);
// Get prime and generator
CryptoPP::Integer integerPrimeA = dhDHA.GetPrime();
CryptoPP::Integer integerGeneratorA = dhDHA.GetGenerator();
// Store prime and generator values
int iCounter = 0;
byte acPrimeA[16] = {0};
for (iCounter = 0; iCounter < 16; iCounter++)
      {
       acPrimeA[iCounter] = integerPrimeA.GetByte(iCounter);
      }
byte cGeneratorA[16]={0};
for (iCounter = 0; iCounter < 16; iCounter++)
      {
       cGeneratorA[iCounter] = integerGeneratorA.GetByte(iCounter);
      }
// Generate key pair
byte acPrivateKeyA[16] = {0};
byte acPublicKeyA[16] = {0};
dhDHA.GenerateKeyPair(randPool, acPrivateKeyA, acPublicKeyA);
cout << "acPrivateKeyA: " << acPrivateKeyA << endl;
cout << "acPublicKeyA: " << acPublicKeyA << endl;
// Bob
// Get prime and generator from Alice
CryptoPP::Integer integerPrimeB;
for (iCounter = 0; iCounter < 16; iCounter++)
      {
       integerPrimeB.SetByte(iCounter, acPrimeA[iCounter]);
      }
CryptoPP::Integer integerGeneratorB;
for (iCounter = 0; iCounter < 16; iCounter++)
      {
       integerGeneratorB.SetByte(iCounter, cGeneratorA[iCounter]);
      }
// Create diffie hellman class based on Alice's p and g
DH dhDHB (integerPrimeB, integerGeneratorB);
// Generate key pair
byte acPrivateKeyB[16] = {0};
byte acPublicKeyB[16] = {0};
dhDHB.GenerateKeyPair(randPool, acPrivateKeyB, acPublicKeyB);
cout << "acPrivateKeyB: " << acPrivateKeyB << endl;
cout << "acPublicKeyB: " << acPublicKeyB << endl;
// To calculate agreed value between Alice and Bob
byte acAgreedValueA[16] = {0};
dhDHA.Agree(acAgreedValueA, acPrivateKeyA, acPublicKeyB, true);
byte acAgreedValueB[16] = {0};
dhDHB.Agree(acAgreedValueB, acPrivateKeyB, acPublicKeyA, true);
cout << "acAgreedValueA: " << acAgreedValueA<< endl;
cout << "acAgreedValueB: " << acAgreedValueB<< endl;
}

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