/*
 * [MakeKeys.java]
 *
 * Summary: Create a public and private RSA encryption key pair.
 *
 * Copyright: (c) 2004-2017 Roedy Green, Canadian Mind Products, http://mindprod.com
 *
 * Licence: This software may be copied and used freely for any purpose but military.
 *          http://mindprod.com/contact/nonmil.html
 *
 * Requires: JDK 1.8+
 *
 * Created with: JetBrains IntelliJ IDEA IDE http://www.jetbrains.com/idea/
 *
 * Version History:
 *  1.4 2006-03-05 reformat with IntelliJ and add Javadoc.
 */
package com.mindprod.transporter;

import java.io.FileOutputStream;
import java.io.IOException;

import static java.lang.System.*;

/**
 * Create a public and private RSA encryption key pair.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 1.4 2006-03-05 reformat with IntelliJ and add Javadoc.
 * @since 2004-06-08
 */
public final class MakeKeys
    {
    /**
     * invoke with: java.exe com.mindprod.transporter.MakeKeys name 512 results to files nameprivatekey.ser and
     * namepublickey.ser Generated keys must be tested before deployment. If they don't work, regenerate the keys.
     * Output goes to files current directory namepublickey.ser and nameprivatekey.ser These files are binary serialised
     * objects, not human-readable.
     *
     * @param args first arg is name for the key pair, e.g. jimmy. second arg is keysize 256 .. 4096. Larger values
     *             offer more security but are much slower to generate keys and encrypt/decrypt. 4096 will take almost
     *             forever.
     */
    public static void main( String[] args )
        {
        if ( args.length != 2 )
            {
            err.println(
                    "You must specify a name for the key, and keysize in bits on the command line, e.g. jimmy 1024" );
            System.exit( 1 );
            }
        String keyname = args[ 0 ];
        // how many bits long the key is.
        int keySize = Integer.parseInt( args[ 1 ] );
        if ( keySize < Tools.SMALLEST_KEYSIZE )
            {
            err.println( "KeySize " + keySize + " too small." );
            keySize = Tools.SMALLEST_KEYSIZE;
            }
        else if ( keySize > Tools.BIGGEST_KEYSIZE )
            {
            err.println( "KeySize " + keySize + " too big." );
            keySize = Tools.BIGGEST_KEYSIZE;
            }
        if ( keySize % 8 != 0 )
            {
            err.println( "KeySize " + keySize + " not a multiple of 8." );
            keySize = keySize / 8 * 8;
            }
        int blockSize = keySize / 8;
        out.println( "generating keys for: "
                     + keyname
                     + "publickey.ser and "
                     + keyname
                     + "privatekey.ser\n"
                     + keySize
                     + " bits. blockSize: "
                     + blockSize
                     + " bytes." );
        out.println( "Please be patient.  You only need to do this once." );
        long start = System.currentTimeMillis();
        PrivateKey p = new PrivateKey( keySize );
        long stop = System.currentTimeMillis();
        out.println( "elapsed " + ( stop - start ) + " milliseconds" );
        try
            {
            p
                    .savePrivateKey( new FileOutputStream( keyname
                                                           + "privatekey.ser" ) );
            /* PrivateKey also contains the public key. */
            p.savePublicKey( new FileOutputStream( keyname
                                                   + "publickey.ser" ) );
            out.println(
                    "Make backups of the generated keys. If you lose them there is no way" );
            out.println( "to read your encryted information. " );
            }
        catch ( IOException e )
            {
            err.println( "key generation failed" );
            System.exit( 1 );
            }
        }
    }