Data Communication network(DCN) program to implement RSA algorithm using C.

Write a program to implement RSA algorithm using C.

Program Code:

#include<stdio.h>

#include<conio.h>

#include<math.h>

#include<string.h>

void main()

{

int p,q,n,e=1,j;

int d=1,i1;

int t1,t2,pt[10],ct[10],rt[10];

char i[10];

clrscr();

printf("\n\nEnter the two prime no. : ");

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

printf("\n\nEnter the message to be sent : ");

scanf("%s",i);

i1=strlen(i);

for(j=0;j<i1;j++)

pt[j]=i[j]-96;

n=p*q;

t1=p-1;

t2=q-1;

while((t1*t2)%e==0)

e++;

for(j=0;j<i1;j++)

ct[j]=((int)pow(pt[j],e))%n;

printf("\nSender Side:");

printf("\n----------------");

printf("\nPublic Key(e)=%d",e);

for(j=0;j<i1;j++)

printf("\nCipher Text = %d",ct[j]);

//Receiver side

printf("\n\nReceiver Side:");

printf("\n-----------------");

while((d*e)%(t1*t2)!=1)

d++;

printf("\n\nPrivate key(d)=%d",d);

for(j=0;j<i1;j++)

{

rt[j]=((int)pow(ct[j],d))%n;

printf("\n\nPlain Text=%d",rt[j]);

}

printf("\n\nDecrypted Message:");

for(j=0;j<i1;j++)

{

rt[j]=rt[j]+96;

printf("%c",rt[j]);

}

getch();

}

Output:

Enter the two prime no. : 3

5

Enter the message to be sent : abcdef

Sender Side:

----------------

Public Key(e)=3

Cipher Text = 1

Cipher Text = 8

Cipher Text = 12

Cipher Text = 4

Cipher Text = 5

Cipher Text = 6

Receiver Side:

-----------------

Private key(d)=3

Plain Text=1

Plain Text=2

Plain Text=3

Plain Text=4

Plain Text=5

Plain Text=6

Decrypted Message: abcdef