RSA.c

//rsa algorithm for encryption
#include<stdio.h>
int modulo(int,int,int);

int main()
{
	int p,q,m;
	printf("\nEnter p and q values (Prime Numbers)");
	scanf("%d%d",&p,&q);
	printf("\nEnter the message:");
	scanf("%d",&m);
	int n=p*q;
	int phi=(p-1)*(q-1);
	
	
	int e=1;
	for (;e<phi;e++)
		if (phi%e!=0) break;

	int d=1;
		for (;d<n;d++)
			if ((d*e)%phi==1) break;


	int c=modulo(m,e,n); //crypt text

	printf("\nc=%d d=%d",c,d);
	printf("\nEncrypted Message=%d",c);
	printf("\nDecrypted Message=%d",modulo(c,d,n));

	return 0;
}

int modulo(int a,int b,int c)
{
	int rem=(a%c);
	b--;
	while (b--)
	{
		rem=(rem*(a%c))%c;
	}
 return rem;
}