#include <iostream>
#include <fstream>
#include <iomanip>
#include <stdio.h>

using namespace std;



void swap ( unsigned char* S, unsigned char* B ){

	char temp = *S;
	*S = *B;
	*B = temp;
}

unsigned char* KeyInit ( char* key, int key_length ){

	unsigned char* s = ( unsigned char* ) calloc ( 256, sizeof ( unsigned char ) );

	for ( int k = 0; k < 256; k++ )
	{
		s[k] = k;
	}

	int j = 0;

	for ( int i = 0; i < 256; i++ )
	{
		j = ( j + s[i] + key[i % key_length] ) % 256;
		swap ( s[i], s[j] );
	}

	return s;

}

void RandomGen ( unsigned char* S, int len, unsigned char* w ){

	int i = 0;
	int j = 0;

	for ( int k = 0; k < len; k++ ){
		i = ( i + 1 ) % 256;
		j = ( j + S[i] ) % 256;
		swap ( S[i], S[j] );
		w[k] = ( S[( S[i] + S[j] ) % 256] );
	}

}

void Encrypt ( char* S, int len, unsigned char* w, unsigned char* X ){

	for ( int k = 0; k < len; k++ )
		X[k] = S[k] ^ w[k];
}

int main ()
{
	char key[] = "Secret";

	/*ifstream file;
	file.open ( "message.txt", ios::binary );
	if ( !file ){

		perror ( "file not found" );
		return 1;
	}*/
	FILE* fin = NULL;
	fpos_t length = 0;
	fin = fopen ( "message.txt", "rb" );
	if ( !fin ){
		perror ( "file not found" );
		return 1;

	}
	fseek ( fin, 0, SEEK_END );
	fgetpos ( fin, &length );

	char* message = ( char* ) calloc ( length, sizeof ( char ) );
	rewind ( fin );

	for ( int i = 0; i < length; i++ )
		fscanf ( fin, "%c", &message[i] );

	fclose ( fin );

	unsigned char* w = ( unsigned char* ) calloc ( length, sizeof ( unsigned char ) );

	unsigned char* S = KeyInit ( key, ( sizeof ( key ) / sizeof ( char ) ) - 1 );

	RandomGen ( S, length, w );

	unsigned char* X = ( unsigned char* ) calloc ( length, sizeof ( unsigned char ) );

	Encrypt ( message, length, w, X );


	FILE* fout = NULL;
	fout = fopen ( "result.txt", "w" );
	if ( !fout ){
		perror ( "file not found" );
		return 2;
	}



	for ( size_t i = 0; i < length; i++ )
		//fputc ((int)i, fout );
		//fwrite ( (int)5, sizeof ( char ), length, fout ) ;
		fprintf ( fout, "%02x", X[i] );
		//printf ( "%02x\n", X[i] );

		fclose ( fout );




	return 0;

}