www.pudn.com > sanpack_rsa_vs2003sln_src.rar > rsa_draft.cpp

#include "stdafx.h" 
// This is a draft version of RSA encryption 
// Improved by sanicle,2006.1  
// 3mn@3mn.net 
#include "rsa_draft.h" 
 
class prime_factory 
{ 
  unsigned np; 
  unsigned *pl; 
  public: 
  prime_factory(); 
  ~prime_factory(); 
  vlong find_prime( vlong & start ); 
}; 
 
// prime factory implementation 
 
static int is_probable_prime( const vlong &p ) 
{ 
  // Test based on Fermats theorem a**(p-1) = 1 mod p for prime p 
  // For 1000 bit numbers this can take quite a while 
  const rep = 4; 
  const unsigned any[rep] = { 2,3,5,7 }; 
  for ( unsigned i=0; i q ) { vlong tmp = p; p = q; q = tmp; } 
  } 
  // Calculate public key 
  { 
    m = p*q; 
    e = 50001; // must be odd since p-1 and q-1 are even 
    while ( gcd(p-vlong(1),e) != vlong(1) || gcd(q-vlong(1),e) != vlong(1) ) e += 2; 
  } 
} 
 
vlong public_key::encrypt( const vlong& plain ) 
{ 
  return modexp( plain, e, m ); 
} 
 
vlong private_key::decrypt( const vlong& cipher ) 
{ 
  // Calculate values for performing decryption 
  // These could be cached, but the calculation is quite fast 
  vlong d = modinv( e, (p-vlong(1))*(q-vlong(1)) ); 
  vlong u = modinv( p, q ); 
  vlong dp = d % (p-vlong(1)); 
  vlong dq = d % (q-vlong(1)); 
 
  // Apply chinese remainder theorem 
  vlong a = modexp( cipher % p, dp, p ); 
  vlong b = modexp( cipher % q, dq, q ); 
  if ( b < a ) b += q; 
  return a + p * ( ((b-a)*u) % q ); 
}