ECKey.java

/* This file is part of Wattzap Community Edition.
 *
 * Wattzap Community Edtion is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Wattzap Community Edition is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Wattzap.  If not, see <http://www.gnu.org/licenses/>.
*/
package ecc.elliptic;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigInteger;

import ecc.Key;
import ecc.Rand;

public class ECKey implements Key {
	/** There are to kinds of keys secret and public */
	protected boolean secret;
	protected BigInteger sk;
	protected ECPoint beta;
	protected EllipticCurve mother;

	/** ECKey generates a random secret key (contains also the public key) */
	public ECKey(EllipticCurve ec) {
		mother = ec;
		secret = true;
		sk = new BigInteger(ec.getp().bitLength() + 17, Rand.om);
		if (mother.getOrder() != null)
			sk = sk.mod(mother.getOrder());
		beta = (mother.getGenerator()).multiply(sk);
		beta.fastCache();
	}

	public ECKey() {
	}

	public String toString() {
		if (secret)
			return ("Secret key: " + sk + " " + beta + " " + mother);
		else
			return ("Public key:" + beta + " " + mother);
	}

	public boolean isPublic() {
		return (!secret);
	}

	public void writeKey(OutputStream out) throws IOException {
		DataOutputStream output = new DataOutputStream(out);
		mother.writeCurve(output);
		output.writeBoolean(secret);
		if (secret) {
			byte[] skb = sk.toByteArray();
			output.writeInt(skb.length);
			output.write(skb);
		}
		byte[] betab = beta.compress();
		output.writeInt(betab.length);
		output.write(betab);
	}

	public Key readKey(InputStream in) throws IOException {
		DataInputStream input = new DataInputStream(in);
		ECKey k = new ECKey(new EllipticCurve(input));
		k.secret = input.readBoolean();
		if (k.secret) {
			byte[] skb = new byte[input.readInt()];
			input.read(skb);
			k.sk = new BigInteger(skb);
		}
		byte[] betab = new byte[input.readInt()];
		input.read(betab);
		k.beta = new ECPoint(betab, k.mother);
		return k;
	}

	/** Turns this key into a public key (does nothing if this key is public) */
	public Key getPublic() {
		Key temp = new ECKey(mother);
		((ECKey) temp).beta = beta;
		((ECKey) temp).sk = BigInteger.ZERO;
		((ECKey) temp).secret = false;
		System.gc();
		return temp;
	}
}