RSA算法原理的简单实现

#include <stdio.h>int candp(int a,int b,int c){ int r=1;b=b+1;while(b!=1){  r=r*a;  r=r%c;  b--;}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 =\n",n);t=(p-1)*(q-1);printf("the t is =\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);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;}getch();}