Program crashed at the start of third loop.

[bdtilove]

Hello every one, I am newbie in C++ Programming, my program always crash at the start of the third loop. Hope every one can help me fix it, here is my code:

  #include <iostream>
#include <iomanip>
#include <bitset>
#include <random>
using namespace std;


/* Hàm chuyển chuỗi sang mã nhị phân */

string nhiphan( string chuoi )
{
    string chuoixuatra;
    for (size_t i = 0; i < chuoi.size(); ++i)
    {
        bitset<8> b = chuoi.c_str()[i];
        chuoixuatra += b.to_string();
    }
    return chuoixuatra;
}

/* Hàm sinh mã khóa ngẫu nhiên */
string khoangaunhien(string dodai)
{

    string ngaunhien;
    for(int i = 0; i < dodai.length(); i++)
    {
        int songaunhien = rand()%2;
        ngaunhien += to_string(songaunhien);
    }
    return ngaunhien;
}


/* Hàm mã hóa */
string mahoa( string chuoicanmahoa)
{
    cout << "Chuyen chuoi tu dang ASCII sang nhi phan:..." << endl;
    string chuoinhinphan = nhiphan(chuoicanmahoa);
    cout << chuoinhinphan << endl;
    cout << "Sinh khoa ma ngau nhien:..." << endl;
    string khoann = khoangaunhien(chuoinhinphan);
    cout << khoann << endl;
    cout << "Chuoi duoc ma hoa o dang Nhi phan la: " << endl;
    for(int i = 0; i<chuoinhinphan.size(); i++)
    {
        cout << (chuoinhinphan[i] ^ khoann[i]);
    }
}

int main()
{
    string khoa;
    cout << endl;
    cout << "Nhap chuoi can ma hoa: " << endl;
    getline(cin, khoa);
    mahoa(khoa);
    cin.ignore();
    return main();
}

[SamuelAdams]

You have multiple loops, which one ?

[bdtilove]

the mahoa() function in main() always crash at third loop