/*
 * [PublicKey.java]
 *
 * Summary: Represents a public RSA key.
 *
 * 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.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;

/**
 * Represents a public RSA key.
 *
 * @author Roedy Green, Canadian Mind Products
 * @version 1.4 2006-03-05 reformat with IntelliJ and add Javadoc.
 * @since 2004-06-08
 */
public class PublicKey
    {
    /**
     * product of two large primes.
     */
    public BigInteger n;

    /**
     * size in bits of key, 512 .. 4096
     */
    public int keySize;

    /**
     * constructor
     *
     * @param publicKeyStream where to find serialised public key information.
     *
     * @throws IOException
     */
    public PublicKey( InputStream publicKeyStream ) throws IOException
        {
        loadKey( publicKeyStream );
        }

    /**
     * Constructor. Do not use
     */
    protected PublicKey()
        {
        }

    /**
     * Save the PublicKey as a serialised object.
     *
     * @param os OutputStream to contain the key
     *
     * @throws IOException
     */
    void savePublicKey( OutputStream os ) throws IOException
        {
        // We avoid serialisation here even though the rest of the package
        // depends on it to make it easier for somone to cannibalise
        // a serialisation-free version.
        // O P E N
        DataOutputStream dos = new DataOutputStream( os );
        // W R I T E
        dos.writeInt( keySize );
        byte[] exportn = n.toByteArray();
        dos.writeInt( exportn.length );
        dos.write( exportn, 0, exportn.length );
        // C L O S E
        dos.close();
        }

    /**
     * read a public key off disk
     *
     * @param publicKeyStream stream containing key (public/private?)
     *
     * @throws IOException if cannot load the publickey
     */
    public void loadKey( InputStream publicKeyStream ) throws IOException
        {
        try
            {
            DataInputStream dis = new DataInputStream( publicKeyStream );
            // R E A D
            keySize = dis.readInt();
            // public key preceded by length
            int nsize = dis.readInt();
            byte[] importn = new byte[ nsize ];
            final int actualSize = dis.read( importn );
            if ( actualSize != nsize )
                {
                throw new IOException( "Public key corrupt" );
                }
            n = new BigInteger( importn );
            // C L O S E
            dis.close();
            }
        catch ( IOException e )
            {
            throw new IOException( "Corrupt private key " + e.getMessage() );
            }
        }
    }