org.jmrtd.protocol.PACEGMWithECDHAgreement Maven / Gradle / Ivy

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/*
 * JMRTD - A Java API for accessing machine readable travel documents.
 *
 * Copyright (C) 2006 - 2017  The JMRTD team
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * $Id: $
 */

package org.jmrtd.protocol;

import java.security.InvalidKeyException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.interfaces.ECPrivateKey;
import java.security.interfaces.ECPublicKey;
import java.security.spec.ECPoint;

import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.jmrtd.Util;

/**
 * An ECDH key agreement implementation, used by PACE protocol for the Generic Mapping
 * case, which is able to return the shared secret in the form of an EC point.
 * 
 * Specifically this implementation is able to keep both X and Y coordinate instead of
 * only returning the X coordinate.
 * 
 * @author The JMRTD team ([email protected])
 *
 * @version $Revision: $
 */
public class PACEGMWithECDHAgreement {

  private ECPrivateKey privateKey;

  /**
   * Initializes the key agreement implementation.
   * 
   * @param privateKey this party's private key
   * 
   * @throws InvalidKeyException if the private key is not an instance of {@link ECPrivateKey}
   */
  public void init(PrivateKey privateKey) throws InvalidKeyException {
    if (!(privateKey instanceof ECPrivateKey)) {
      throw new InvalidKeyException("Not an ECPrivateKey");
    }
    this.privateKey = (ECPrivateKey)privateKey;
    
  }

  /**
   * Performs a key agreement protocol.
   * 
   * @param publicKey the other party's public key
   * 
   * @return the resulting shared secretin the form of an EC point
   * 
   * @throws InvalidKeyException if the provided key is not an instance of {@link ECPublicKey}
   * @throws IllegalStateException if this key agreement has not been initialized
   */
  public ECPoint doPhase(PublicKey publicKey) throws InvalidKeyException, IllegalStateException {
    if (privateKey == null) {
      throw new IllegalStateException("Not initialized!");
    }
    
    if (!(publicKey instanceof ECPublicKey)) {
      throw new InvalidKeyException("Not an ECPublicKey");
    }
    
    ECPublicKeyParameters pub = Util.toBouncyECPublicKeyParameters((ECPublicKey)publicKey);

    org.bouncycastle.math.ec.ECPoint p = pub.getQ().multiply(Util.toBouncyECPrivateKeyParameters(privateKey).getD()).normalize();
    if (p.isInfinity()) {
      throw new IllegalStateException("Infinity");
    }
    return Util.fromBouncyCastleECPoint(p);
  }
}