RSA暗号　p,q,dを自分で入力するタイプ。

rsa.c

#include <stdio.h>

int bainari(int e_10to2,int n,int m)
{
int num_2[200],amari,count,i=0,bi,bi1,ri,ri1;
	while(e_10to2 >= 1){
		amari = e_10to2 % 2;
		e_10to2 = e_10to2 / 2;
		num_2[i] = amari;
		i++;
	}num_2[i] = 0;
	num_2[i] = 0;

	count = i - 1;

	bi1 = m;
	bi  = m;
	ri1 = 1;
	for (int k = 0; k <= count; k++)
	{
		if(k == 0 && num_2[k] == 1){
		ri = bi * ri1 % n;
		ri1 = ri;
		bi1 = bi;
		}else if(k == 0 && num_2[k] == 0){
		bi = bi1 * bi1 % n;
		ri1 = ri;
		bi1 = bi;
		}else if(num_2[k] == 0){
		bi = bi1 * bi1 % n;
		ri1 = ri;
		bi1 = bi;
		}else{
		bi = bi1 * bi1 % n;
		ri = bi * ri1 % n;
		ri1 = ri;
		bi1 = bi;
		}
	}

	return ri;

}


int yukuri(int modafter,int ddd){
	int gi,gi1,gi2,ri,ri1,ri2,ti,ti1=1,ti2=0;

	gi2 = 0;
	ri2 = modafter;
	gi1 = modafter / ddd;
	ri1 = ddd;
	do{
		ri = ri2 - gi1 * ri1;
		ti = ti2 - gi1 * ti1;
		gi = ri1 / ri;

		gi2 = gi1;
		gi1 = gi;
		ri2 = ri1;
		ri1 = ri;
		ti2 = ti1;
		ti1 = ti;
	}while(ri != 1);

	ti = modafter + ti;

	return ti;
}


int main()
{
	int p,q,d,n,e,m,modafter,c,search,flag;

	printf("秘密鍵p(素数)を入力\n>>");
	scanf("%d",&p);
	printf("秘密鍵q(素数)を入力\n>>");
	scanf("%d",&q);
	printf("秘密鍵d(整数)を入力\n>>");
	scanf("%d",&d);

	printf("秘密鍵：p->%d,q->%d,d->%d\n",p,q,d);

	modafter = (p-1)*(q-1);
	e = yukuri(modafter,d);
	n = p * q;
	printf("公開鍵：n->%d,e->%d\n",n,e );


	do{
		printf("暗号化したいときは「0」を\n復号したい時は「1」を入力\n>>");
		scanf("%d",&search);
		if(search == 0){
			printf("暗号化したい数字を入力\n>>");
			scanf("%d",&m);	
		
			c = bainari(e,n,m);		

			printf("暗号化：c->%d\n\n",c );

			printf("まだ暗号化、復号を続けたい場合は「1」を\n終了する場合はそれ以外の数字を入力\n>>");
			scanf("%d",&flag);
		}else if(search == 1){
			printf("復号したい数字を入力\n>>");
			scanf("%d",&c);	
		
			m = bainari(d,n,c);		

			printf("復号結果：m->%d\n\n",m );	

			printf("まだ暗号化、復号を続けたい場合は「1」を\n終了する場合はそれ以外の数字を入力\n>>");
			scanf("%d",&flag);
		}else{
			printf("「0」か「1」を入力してください。\n");
			flag = 1;
		}
	}while(flag == 1);

	printf("終了\n");


	return 0;


}