CODEWITHSUNDEEP
c++visual-c++encryptionrsa
Raja
Raja

Reputation: 105

error in encryption program

#include<iostream>
#include<math.h>
#include<string>
#include<cstring>

using namespace std;

 int gcd(int n,int m)
   {
   if(m<=n && n%m ==0)
   return m;
   if(n<m)
   return gcd(m,n);
   else
   return gcd(m,n%m);
  }

 int REncryptText(int m)
  {int b = double(m);
      int p = 11, q = 3;
      int e = 3;
      double n = p * q;
      int phi = (p - 1) * (q - 1);

      int check1 = gcd(e, p - 1);
      int check2 = gcd(e, q - 1);

      int check3 = gcd(e, phi);

            //     // Compute d such that ed ≡ 1 (mod phi)
            //i.e. compute d = e-1 mod phi = 3-1 mod 20
            //i.e. find a value for d such that phi divides (ed-1)
            //i.e. find d such that 20 divides 3d-1.
            //Simple testing (d = 1, 2, ...) gives d = 7

   //   double d = Math.Pow(e, -1) % phi;

      int d = 7;

      // public key = (n,e) // (33,3)
      //private key = (n,d) //(33 ,7)

      double g = pow(b,e);

      double ciphertext = g % n;  // here error
      // Now say we want to encrypt the message m = 7, c = me mod n = 73 mod 33 = 343 mod 33 = 13. Hence the ciphertext c = 13. 

      //double decrypt = Math.Pow(ciphertext, d) % n;
      return int(ciphertext);
  }

int main()
    {
    char plaintext[80],str[80];

    cout<<" enter the text you want to encrpt";
    cin.get(plaintext,79);

    int l =strlen(plaintext);
    for ( int i =0 ; i<l ; i++)
        { 
        char s = plaintext[i];
        str[i]=REncryptText(static_cast<char>(s));
        }

    for ( int i =0 ; i<l ; i++)
        { 
        cout<<"the encryption of string"<<endl;
            cout<<str[i];
        }


    return 0;
    }

now the error coming error C2297: '%' : illegal, right operand has type 'double' error C2668: 'pow' : ambiguous call to overloaded function

Upvotes: 0

Views: 325

Answers (1)

Fred Foo
Fred Foo

Reputation: 363807

  1. You forgot to #include <cstring> to get strlen declared
  2. The line int ciphertext = g % n; in REncryptText won't work since you can't do integer modulo on a double. You need to find a better way to do modular exponentiation; search the web or pick up a good algorithms textbook, this isn't as trivial a problem as it may seem.

Upvotes: 2

Related Questions