RSA Algorithm Network Security

This program is for implementing RSA Algorithm. This is a part of Mumbai University MCA Colleges Data Communication and Networking MCA Sem 4
#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;

}

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);

}

void main()

{

int p,q,s;

clrscr();

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();

}



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