ecc1-8.java

package orig;
import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.ECFieldFp;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.ECPrivateKeySpec;
import java.security.spec.EllipticCurve;
import java.security.spec.InvalidKeySpecException;
import javax.crypto.KeyAgreement;
import java.security.spec.ECPublicKeySpec;

public class EccJava521 {
    public static void main(String[] args) throws Exception {
        //g the generator which is also known as the base point.
        ECPoint point = new ECPoint(
                // gx
                new BigInteger("26617408020502170632287687167233609607298591687569" +
                        "73147706671368418802944996427808491545080627771902" +
                        "35209424122506555866215711354557091681416163731589" +
                        "5999846"),
                // gy
                new BigInteger("37571800257700204635455072244911836035944551347697" +
                        "62486694567779615544477440556316691234405012945539" +
                        "56214444453728942852258566672919658081012434427757" +
                        "8376784"));
        
        final ECParameterSpec P521 = new ECParameterSpec(
        new EllipticCurve(
            // field the finite field that this elliptic curve is over.
            new ECFieldFp(new BigInteger("68647976601306097149819007990813932172694353001433" +
                    "05409394463459185543183397656052122559640661454554" +
                    "97729631139148085803712198799971664381257402829111" +
                    "5057151")),
            // a the first coefficient of this elliptic curve.
            new BigInteger("68647976601306097149819007990813932172694353001433" +
                    "05409394463459185543183397656052122559640661454554" +
                    "97729631139148085803712198799971664381257402829111" +
                    "5057148"),
            // b the second coefficient of this elliptic curve.
            new BigInteger("10938490380737342745111123907668055699362075989516" +
                    "83748994586394495953116150735016013708737573759623" +
                    "24859213229670631330943845253159101291214232748847" +
                    "8985984")
        ),
       point,
        // Order n
        new BigInteger("68647976601306097149819007990813932172694353001433" +
                "05409394463459185543183397655394245057746333217197" +
                "53296399637136332111386476861244038034037280889270" +
                "7005449"),
        1);
        ECParameterSpec ecParameterSpec = P521;
        KeyFactory keyFactory = KeyFactory.getInstance("EC");
        ECPublicKeySpec pubKeySpec = new ECPublicKeySpec(point, ecParameterSpec);
        PublicKey publicKey = keyFactory.generatePublic(pubKeySpec);
        getAgreedKey(new BigInteger("6864797660130609714981900799081393217269435300143305409394463459185543183397655394245057746333217197532963996371363321113864768612440380340372808892707005431"),keyFactory, publicKey, ecParameterSpec);
    }
    private static byte[] getAgreedKey(BigInteger counter, KeyFactory keyFactory, PublicKey publicKey,  ECParameterSpec ecParameterSpec) throws NoSuchAlgorithmException, InvalidKeyException, InvalidKeySpecException {
        ECPrivateKeySpec privateKeySpec = new ECPrivateKeySpec(counter, ecParameterSpec);
        PrivateKey recoveredPrivateKey = keyFactory.generatePrivate(privateKeySpec);
        KeyAgreement keyAgreement = KeyAgreement.getInstance("ECDH");
        keyAgreement.init(recoveredPrivateKey);
        keyAgreement.doPhase(publicKey, true);
 
        return keyAgreement.generateSecret();
    }
}