#include <stdio.h>
#include <QuickCrypt.h>

#define BUFF_SIZE  1024

/* performs DESX file encryption/decryption in OFB mode */
int EncryptDecryptFile( const char* filenamefrom, const char* filenameto, const unsigned char* iv, const unsigned char* key )
{
    FILE *filefrom, *fileto;
    unsigned char buff[ BUFF_SIZE ];
    unsigned char context[ SLC_DESX_CONTEXTSIZE ];
    int fs = 0;

    /***** Open files ***********************/

    filefrom = fopen( filenamefrom, "rb" );

    if( filefrom == NULL )
    {
        printf( "\nCould not open file: %s", filenamefrom );
        return 0;
    }

    fileto = fopen( filenameto, "wb" );

    if( fileto == NULL )
    {
        printf( "\nCould not open file: %s", filenameto );
        fclose( filefrom );
        return 0;
    }

    /***** Initialize context ****************/

    SL_DESX_Init( context, SLC_ENCRYPT, key, SLC_DESX_DEFAULTKEYSIZE );
    SL_OFB_Init( context, iv, fs );

    /***** Encrypt/Decrypt file **************/

    while( !feof( filefrom ) )
    {
        unsigned int buffsize = fread( buff, sizeof( char ), BUFF_SIZE, filefrom );
        if( ferror( filefrom ) )
        {
            printf( "\nAn error occurred when accessing the file: %s", filenamefrom );
            fclose( filefrom );
            fclose( fileto );
            return 0;
        }

        SL_OFB_Process( context, buff, buff, buffsize ); /* in-place encryption/decryption */

        fwrite( buff, sizeof( char ), buffsize, fileto );
    }

    /***** Close files ***********************/

    fclose( filefrom );
    fclose( fileto );

    return 1;
}

int main()
{
    char buff[10];

    char filename[256];     /* Initial file   */
    char filenameencr[256]; /* Encrypted file */
    char filenamedecr[256]; /* Decrypted file */

    /***** Define key & iv ********************************************************/

    char key[SLC_DESX_DEFAULTKEYSIZE] = 
    {
        's', 'e', 'c', 'r', 'e', 't', 'l', 'y',

        '9', '6', '7', '1', '2', '9', '2', '7',

        '0', '1', '2', '2', '0', '0', '5', '7'
    };

    unsigned char iv[SLC_DESX_BLOCKSIZE] = 
    {
        0x41, 0x3E, 0xF0, 0xA1, 0xC6, 0x11, 0xE5, 0x50
    };

    do
    {
        /***** Get file to encrypt (Initial file) *********************************/

        printf( "Enter the full name of the file to encrypt:\n" );
        gets( filename );

        /***** Get file to store the result of encryption (Encrypted file) ********/

        printf( "Enter the full name of the file to store the result of encryption:\n" );
        gets( filenameencr );

        /***** Encrypt file *******************************************************/

        if( EncryptDecryptFile( filename, filenameencr, iv, (const unsigned char*)key ) )
        {
            /***** Get file to store the result of decryption (Decrypted file) ****/

            printf( "Enter the full name of the file to store the result of decryption:\n" );
            gets( filenamedecr );

            /***** Decrypt file ***************************************************/
            
            EncryptDecryptFile( filenameencr, filenamedecr, iv, (const unsigned char*)key );

            /* At this point compare Initial file with Decrypted file. They must be identical. */
        }

        /***** Continue? **********************************************************/
        
        printf( "\nContinue (Y/N)?" );
        gets( buff );

    } while( *buff == 'Y' || *buff == 'y' );

    return 0;
}