77 lines
1.4 KiB
C++
77 lines
1.4 KiB
C++
/*
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* Cramer-Shoup Public Key Cryptography
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*
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* This program generates the common values q, p, g1 and g2 to a file
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* common.crs
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*
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* Requires: big.cpp
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*/
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#include <iostream>
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#include <fstream>
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#include "big.h"
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using namespace std;
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#define PBITS 1024
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#define QBITS 160
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Miracl precision=100;
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int main()
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{
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ofstream common("common.crs"); // construct file I/O streams
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Big p,q,h,t,s,r,n,g;
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long seed;
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cout << "Enter 9 digit random number seed = ";
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cin >> seed;
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irand(seed);
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get_mip()->IOBASE=16;
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/* generate q */
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forever
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{
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n=rand(QBITS-2,2); /* QBIT-2 bit number, base 2 */
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q=2*n+1;
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while (!prime(q)) q+=2;
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if (bits(q)>=QBITS) continue;
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break;
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}
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cout << "q= " << q << endl;
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common << PBITS << endl;
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common << q << endl;
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/* generate p */
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t=(pow((Big)2,PBITS)-1)/(2*q);
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s=(pow((Big)2,PBITS-1)-1)/(2*q);
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forever
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{
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n=rand(t);
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if (n<s) continue;
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p=2*n*q+1;
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if (prime(p)) break;
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}
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cout << "p= " << p << endl;
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common << p << endl;
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/* generate g1 */
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do {
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h=rand(p-1);
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g=pow(h,(p-1)/q,p);
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} while (g==1);
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cout << "g1= " << g << endl;
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common << g << endl;
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/* generate g2 */
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do {
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h=rand(p-1);
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g=pow(h,(p-1)/q,p);
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} while (g==1);
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cout << "g2= " << g << endl;
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common << g << endl;
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return 0;
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}
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