eckey.java

来自「java写的椭圆曲线加密(ECC)算法源码」· Java 代码 · 共 72 行

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);
	if (mother.getOrder() != null) sk=sk.mod(mother.getOrder());
	beta=(mother.getGenerator()).multiply(sk);
	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;
    }
}