I just have a program to implement RSA encryption, and it runs but when I try to encrypt a message it crashes. When I bebug it won't show any error, What is the issue,How Can I fix the program?
#include<iostream>
#include<cmath>
using namespace std;
#define MAXLENGTH 500
int size = 0;
int p, q; //the two prime numbers
int n, phi; //n = p * q，phi = (p-1) * (q-1)
int e; //{e, n}the public key
int d; //{d, n}the private key
int i, j ;
int clear[MAXLENGTH], Ciphertext[MAXLENGTH];//used to store add // dense before the bright // text and encrypted ciphertext
int DecryptionText[MAXLENGTH];//Store the decrypted plaintext
void Encryption()
{
//encrypt method
cout << " enter two prime number p and q：" ;
cin >> p >> q ;
cout << " p = " << p << ", q = " << q << endl;
n = p * q;//compute n，
phi = (p - 1) * ( q - 1 );//compute the totient of the product
cout << " n = " << n << ", phi = " << phi << endl;
cout << " choose number between[0，" << phi - 1 << "] " << phi << " coprime to 3120：";
cin >> e;
float d0;
for( int i = 1; ; i++)
{///compute modular multiplicative inverse of e * d ≡ 1 (mod phi)
d0 = (float)(phi*i+1) / e;
if( d0 - (int)d0 == 0 )
break;
}
d = (int)d0;
cout << endl;
cout << " e = " << e << ", d = " << d << endl;
cout << " The public key is {e,n} = {" << e << "," << n << "}" << endl;
cout << " The private key is {d,n} = {" << d << "," << n << "}" << endl;
cout << endl;
cout << " enter a prime number to encrypt less than " << n << " positive integer（ -1 to end）：" << endl;
cout << " The plaintext before encryption：";
for( i = 0; i < MAXLENGTH; i++)
Ciphertext[i] = 1;
int count;
for(int j = 0; j<MAXLENGTH; j++)
{
cin >> clear[j];
if( clear[j] == -1 )
break;
count = e;
while(count > 0)
{
//to encrypt Ciphertext =（clear）^ e mod n
Ciphertext[j] = (Ciphertext[j] * clear[j]) % n;
count-- ;
}
}
cout << " the Ciphertext is：" ;
size = j;//the length of ciphertext
for(int k=0; k<j; k ++)
cout << Ciphertext[k] << " ";
cout << endl ;
}
void Decryption()
{
//decrypt method
for(int i = 0; i < MAXLENGTH; i++)
DecryptionText[i] = 1;
int count;
for(int j = 0; j < size; j++)
{
count = d;
while(count > 0)
{//compute DecryptionText =（Ciphertext）^ d (mod n)
DecryptionText[j] = ((DecryptionText[j] * Ciphertext[j]) %n);
count-- ;
}
}
cout << " ：";
int k;
for( int k = 0; k < size; k ++)
cout << DecryptionText[k] << " ";
cout << endl ;
cout << " The plaintext before encryption：";
for( k = 0; k < size; k++)
cout << clear[k] << " ";
cout << endl;
}
void main()
{
Encryption();
char c;
cout << endl;
cout << "want decrypt （Y or N）: ";
cin >> c;
if(c == 'y' || c == 'Y')
Decryption();
else
return ;
}
