WAP of Rivets Shamir Adelman(RSA) algorithm

#include<stdio.h>

#include<conio.h>

int phi,M,n,e,d,C,FLAG;

int check()

{

int i;

for(i=3;e%i==0 && phi%i==0;i+2)

{

FLAG = 1;

return 0;

}

FLAG = 0;

}

void encrypt()

{

int i;

C = 1;

for(i=0;i< e;i++)

C=C*M%n;

C = C%n;

printf("\n\tEncrypted keyword : %d",C);

}

void decrypt()

{

int i;

M = 1;

for(i=0;i< d;i++)

M=M*C%n;

M = M%n;

printf("\n\tDecrypted keyword : %d",M);

}

int main()

{

int p,q,s;

printf("Enter Two Relatively Prime Numbers\t: ");

scanf("%d%d",&p,&q);

n = p*q;

phi=(p-1)*(q-1);

printf("\n\tF(n)\t= %d",phi);

do

{

printf("\n\nEnter e\t: ");

scanf("%d",&e);

check();

}while(FLAG==1);

d = 1;

do

{

s = (d*e)%phi;

d++;

}while(s!=1);

d = d-1;

printf("\n\tPublic Key\t: {%d,%d}",e,n);

printf("\n\tPrivate Key\t: {%d,%d}",d,n);

printf("\n\nEnter The Plain Text\t: ");

scanf("%d",&M);

encrypt();

printf("\n\nEnter the Cipher text\t: ");

scanf("%d",&C);

decrypt();

getch();

}

/*************** OUTPUT *****************

Enter Two Relatively Prime Numbers : 7 17

F(n) = 96

Enter e : 5

Public Key : {5,119}

Private Key : {77,119}

Enter The Plain Text : 19

Encrypted keyword : 66

Enter the Cipher text : 66

Decrypted keyword : 19 */