ECKey.java

//package ecc.elliptic;

//import ecc.Key;
//import ecc.Rand;
import java.math.BigInteger;
import java.io.*;

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);			//sk is a random num.
		if (mother.getOrder() != null) sk=sk.mod(mother.getOrder());		//sk=sk%order
		beta=(mother.getGenerator()).multiply(sk);				//beta=generator*sk (public key)
		beta.fastCache();
	}

	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;
	}

	/** Turns this key into a public key (does nothing if this key is public) */
	public Key getpublic() throws Exception 
	{
		Key temp = new ECKey(mother);

		int[] k = new int[mother.ppodbf.intValue()];

		for(int i=0;i<mother.ppodbf.intValue();i++) 
		{
			if(i==0) k[i] =0;
			else if(k[i-1]==0) k[i]=1;
			else k[i]=0;
		}

		ECPoint R0 = ((ECKey)temp).beta;
		ECPoint R1 = ((ECKey)temp).beta.multiply(new BigInteger("2"));

		for(int i=mother.ppodbf.intValue();i>=0;i--) 
		{
			if(k[i]==0)       
			{
				R1 = R0.add(R1);
				R0 = R0.multiply(new BigInteger("2"));
			}
			else 
			{
				R0 = R0.add(R1);
				R1 = R1.multiply(new BigInteger("2"));
			}
		}

		((ECKey)temp).beta = R0;
		((ECKey)temp).sk = BigInteger.ZERO;       
		((ECKey)temp).secret = false;
		System.gc();
		return temp;
	}
}