rsa2.c

RSA一个简单的C语言算法实现

#include <stdio.h>
int candp(int m_c,int e_d,int n)
{ int r=1;
  e_d=e_d+1;
  while(e_d!=1)
  {
    r=r*m_c;
    r=r%n;
    e_d--;
  }
  printf("%d\n",r);
  return r;
}
void main()
{
  int p,q,e,d,m,n,t,c,r;
  char s;
  printf("please input the p,q: ");
  scanf("%d%d",&p,&q);
  n=p*q;
  printf("the n is %3d\n",n);
  t=(p-1)*(q-1);
  printf("the t is %3d\n",t);
  printf("please input the e: ");
  scanf("%d",&e);
  if(e<1||e>t)
  {
     printf("e is error,please input again: ");
     scanf("%d",&e);
  }
  d=1;
  while(((e*d)%t)!=1)   d++;
  printf("then caculate out that the d is %d\n",d);
  while(r!=0)
  {
    printf("the cipher please input 1\n");
    printf("the plain  please input 2\n");
    scanf("%d",&r);
    switch(r)
    {
      case 1: printf("input the m: ");
              scanf("%d",&m);
              c=candp(m,e,n);
              printf("the cipher is %d\n",c);break;
      case 2: printf("input the c: ");
              scanf("%d",&c);
              m=candp(c,d,n);
              printf("the cipher is %d\n",m);break;
      default: exit(0);
    }
  }
  getch();
}