RSA ALGORITHM IMPLEMENTATION



/********** RSA PROGRAM ***********/
/*d value should be less than 11 bcoz (c^d)modn can't be computed using available
datatypes*/
#include<stdio.h>
#include<string.h>
#include<math.h>
void main()
{
char a[]={"0ABCDEFGHIJKLMNOPQRSTUVWXYZ"};
int n,i,j,s,n2,k1,p,q,d,m1,e1,l5,z,p2[30],s1,c[30];
unsigned long int l3,m,l4,k2;
double l2,l1,l6;
float e,l;
char p1[30];
clrscr();
printf("enter two prime numbers p and q\n");
scanf("%d %d",&p,&q);
do{
n=p*q;
if(n<26)
{ printf("\n n value is not large enough.\nplease select p, q value such that p*q is greater than
26");
scanf("%d %d",&p,&q);}
}
while(n<26);
z=((p-1)*(q-1));
printf("enter the value of d:\n");
scanf("%d",&d);
for(j=1;j<z;j++)
{
if((j*d)%z==1)
break;
}
e=j;
printf("%d %d %f\n",n,z,e);
printf("ENCRYPTION-CIPHERTEXT");
printf("enter the plain text\n");
scanf("%s",p1);
for(i=0;i<strlen(p1);i++)
{
for(j=1;j<strlen(a);j++)
{
if(a[j]==p1[i])
{
s=j;
break;
}
else
continue;
}
printf("%d",s);
e1=(int)e;
l1=pow(((double)s),((double)e1));
k2=fmod(l1,(double)n);
printf("\n%lu\n",k2);
c[i]=(int)k2;
printf("cipher:%d\n",c[i]);
}
printf("\n");
for(i=0;i<strlen(p1);i++)
{
l2=(pow(((double)c[i]),((double)d)));
m=fmod(l2,(double)n);
m1=(int)m;
printf(" %c\n",a[m1]);}
getch();
}
RSA OUTPUT
Enter two prime numbers p and q
3 11
enter the value of d:
7
33 20 3.000000
ENCRYPTION-CIPHER TEXT
enter the plain text
SUZANNE
19
28
cipher:28
21
21
cipher:21
26 20 cipher:20
1 1 cipher:1
14 5 cipher:5
14 5 cipher:5
5 26 cipher:26
S U Z A N N E
s

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RSA ALGORITHM IMPLEMENTATION[/b]


This CODING IS NOT WORKING.......
/********** RSA PROGRAM ***********/
/*d value should be less than 11 bcoz (c^d)modn can't be computed using available
datatypes*/
#include<stdio.h>
#include<string.h>
#include<math.h>
void main()
{
char a[]={"0ABCDEFGHIJKLMNOPQRSTUVWXYZ"};
int n,i,j,s,n2,k1,p,q,d,m1,e1,l5,z,p2[30],s1,c[30];
unsigned long int l3,m,l4,k2;
double l2,l1,l6;
float e,l;
char p1[30];
clrscr();
printf("enter two prime numbers p and q\n");
scanf("%d %d",&p,&q);
do{
n=p*q;
if(n<26)
{ printf("\n n value is not large enough.\nplease select p, q value such that p*q is greater than
26");
scanf("%d %d",&p,&q);}
}
while(n<26);
z=((p-1)*(q-1));
printf("enter the value of d:\n");
scanf("%d",&d);
for(j=1;j<z;j++)
{
if((j*d)%z==1)
break;
}
e=j;
printf("%d %d %f\n",n,z,e);
printf("ENCRYPTION-CIPHERTEXT");
printf("enter the plain text\n");
scanf("%s",p1);
for(i=0;i<strlen(p1);i++)
{
for(j=1;j<strlen(a);j++)
{
if(a[j]==p1[i])
{
s=j;
break;
}
else
continue;
}
printf("%d",s);
e1=(int)e;
l1=pow(((double)s),((double)e1));
k2=fmod(l1,(double)n);
printf("\n%lu\n",k2);
c[i]=(int)k2;
printf("cipher:%d\n",c[i]);
}
printf("\n");
for(i=0;i<strlen(p1);i++)
{
l2=(pow(((double)c[i]),((double)d)));
m=fmod(l2,(double)n);
m1=(int)m;
printf(" %c\n",a[m1]);}
getch();
}
RSA OUTPUT
Enter two prime numbers p and q
3 11
enter the value of d:
7
33 20 3.000000
ENCRYPTION-CIPHER TEXT
enter the plain text
SUZANNE
19
28
cipher:28
21
21
cipher:21
26 20 cipher:20
1 1 cipher:1
14 5 cipher:5
14 5 cipher:5
5 26 cipher:26
S U Z A N N E
s

[/quote]