RSA Algorithm For Numbers and Char values - c++

Question

I'm not a programming expert. I'm new to cryptography and I had gone through the security algorithm RSA. I wrote the code like this:
#include<math.h>
#include<iostream>
#include<cmath>
#include<Windows.h>
using namespace std;
class rsacrypto
{
long publickey;
long privatekey;
long modl; //Modulus
public :
rsacrypto(); //To be used to just generate private and public keys.
rsacrypto(long &,long &,long &);//To be used just to generate private and public keys.
rsacrypto(long key,long modulus) // Should be used when a data is to be encrypted or decrypted using a key.
{
publickey = privatekey = key;
modl = modulus;
}
long ret_publickey()
{
return publickey;
}
long ret_privatekey()
{
return privatekey;
}
long ret_modulus()
{
return modl;
}
void encrypt(char *);
void decrypt(char *);
int genrndprimes(int, int);
int genrndnum(int, int);
int totient(int);
int gcd (int, int);
int mulinv(int, int);
boolean isPrime(long);
};
rsacrypto::rsacrypto()
{
long p1,p2; //Prime numbers
long n = 0; //Modulus
long phi =0; //Totient value.
long e = 0; //Public key exponent.
long d = 0; //Private key exponent.
p1 = genrndprimes(1,10);
Sleep(1000);
p2 = genrndprimes(1,10);
n = p1*p2;
phi = (p1-1)*(p2-1);
e = genrndnum(2,(phi-1));
while(gcd(e,phi)!=1)
{
e = genrndnum(2,(phi-1));
}
d = mulinv(e, phi);
cout<<"Public Key=("<<e<<","<<n<<")"<<"\n";
cout<<"Private Key=("<<d<<","<<n<<")"<<"\n";
privatekey = e;
publickey = d;
modl = n;
int m=11;
int en=0, decr=0;
//Encryption
en=(long)pow((double)m,d)%n;
cout<<en<<"\n";
//Decryption
decr=(long)pow((double)en,e)%n;
cout<<decr;
}
/*
void rsacrypto::encrypt(char *dat)
{
long siz = strlen(dat);
for(long i=0;i<siz;i++)
{
dat[i]=(long)pow((double)dat[i],publickey)%modl;
cout<<i<<"="<<dat[i]<<"\n";
}
}
void rsacrypto::decrypt(char *datn)
{
long sizz = strlen(datn);
for(long i=0;i<sizz;i++)
{
datn[i]=(long)pow((double)datn[i],privatekey)%modl;
}
cout<<datn;
}*/
int rsacrypto::mulinv(int a, int b)
{
int b0 = b, t, q;
int x0 = 0, x1 = 1;
if (b == 1) return 1;
while (a > 1) {
q = a / b;
t = b, b = a % b, a = t;
t = x0, x0 = x1 - q * x0, x1 = t;
}
if (x1 < 0) x1 += b0;
return x1;
}
int rsacrypto::genrndprimes(int a, int b){
long pivot;
do{
pivot= rand() % b + a;
if (isPrime(pivot))
return pivot;
} while (1==1);
}
boolean rsacrypto::isPrime(long pivot) {
if(pivot <= 1)
return false;
int root = sqrt((double)pivot);
//start at 2 because all numbers are divisible by 1
for(int x = 2; x <= root; x++) //You only need to check up to and including the root
{
if(pivot % x == 0)
return false;
}
return true;
}
int rsacrypto::genrndnum(int a, int b){
long pivot;
pivot= rand() % b + a;
return pivot;
}
int rsacrypto::gcd ( int a, int b )
{
int c;
while ( a != 0 ) {
c = a; a = b%a; b = c;
}
return b;
}
void main()
{
rsacrypto m;
system("pause");
}
But I would like to make this code work for hexa decimal values. I don't know how to do that. I'm not a programming expert. Any help would be sinscierly appreciated. Thankyou.

Answer 1

I guess your problem is to transfer the double values (hex decimal values) into char values first. Then you can use the existing code to encrypt/decrypt the char values.
There are two ways to convert the double values into char values:
Convert each double into two char's as its printable/readable form, e.g., 123.455 -> "123.456";
I refer some code from this discussion:
#include <sstream>
stringstream ss;
ss << myDouble;
const char* str = ss.str().c_str();
ss >> myOtherDouble;
Convert each double into two char's as its byte form;
Please see this discussion:
Use a union:
union {
double d[2];
char b[sizeof(double) * 2];
};
Or reinterpret_cast:
char* b = reinterpret_cast<double*>(d);
Now, after converting your double values into char values, we can directly utilize the existing code to encrypt our data.