| /* |
| * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code 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 |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package java.security.spec; |
| |
| import java.math.BigInteger; |
| import java.util.Arrays; |
| |
| /** |
| * This immutable class holds the necessary values needed to represent |
| * an elliptic curve. |
| * |
| * @see ECField |
| * @see ECFieldFp |
| * @see ECFieldF2m |
| * |
| * @author Valerie Peng |
| * |
| * @since 1.5 |
| */ |
| public class EllipticCurve { |
| |
| private final ECField field; |
| private final BigInteger a; |
| private final BigInteger b; |
| private final byte[] seed; |
| |
| // Check coefficient c is a valid element in ECField field. |
| private static void checkValidity(ECField field, BigInteger c, |
| String cName) { |
| // can only perform check if field is ECFieldFp or ECFieldF2m. |
| if (field instanceof ECFieldFp) { |
| BigInteger p = ((ECFieldFp)field).getP(); |
| if (p.compareTo(c) != 1) { |
| throw new IllegalArgumentException(cName + " is too large"); |
| } else if (c.signum() < 0) { |
| throw new IllegalArgumentException(cName + " is negative"); |
| } |
| } else if (field instanceof ECFieldF2m) { |
| int m = ((ECFieldF2m)field).getM(); |
| if (c.bitLength() > m) { |
| throw new IllegalArgumentException(cName + " is too large"); |
| } |
| } |
| } |
| |
| /** |
| * Creates an elliptic curve with the specified elliptic field |
| * <code>field</code> and the coefficients <code>a</code> and |
| * <code>b</code>. |
| * @param field the finite field that this elliptic curve is over. |
| * @param a the first coefficient of this elliptic curve. |
| * @param b the second coefficient of this elliptic curve. |
| * @exception NullPointerException if <code>field</code>, |
| * <code>a</code>, or <code>b</code> is null. |
| * @exception IllegalArgumentException if <code>a</code> |
| * or <code>b</code> is not null and not in <code>field</code>. |
| */ |
| public EllipticCurve(ECField field, BigInteger a, |
| BigInteger b) { |
| this(field, a, b, null); |
| } |
| |
| /** |
| * Creates an elliptic curve with the specified elliptic field |
| * <code>field</code>, the coefficients <code>a</code> and |
| * <code>b</code>, and the <code>seed</code> used for curve generation. |
| * @param field the finite field that this elliptic curve is over. |
| * @param a the first coefficient of this elliptic curve. |
| * @param b the second coefficient of this elliptic curve. |
| * @param seed the bytes used during curve generation for later |
| * validation. Contents of this array are copied to protect against |
| * subsequent modification. |
| * @exception NullPointerException if <code>field</code>, |
| * <code>a</code>, or <code>b</code> is null. |
| * @exception IllegalArgumentException if <code>a</code> |
| * or <code>b</code> is not null and not in <code>field</code>. |
| */ |
| public EllipticCurve(ECField field, BigInteger a, |
| BigInteger b, byte[] seed) { |
| if (field == null) { |
| throw new NullPointerException("field is null"); |
| } |
| if (a == null) { |
| throw new NullPointerException("first coefficient is null"); |
| } |
| if (b == null) { |
| throw new NullPointerException("second coefficient is null"); |
| } |
| checkValidity(field, a, "first coefficient"); |
| checkValidity(field, b, "second coefficient"); |
| this.field = field; |
| this.a = a; |
| this.b = b; |
| if (seed != null) { |
| this.seed = seed.clone(); |
| } else { |
| this.seed = null; |
| } |
| } |
| |
| /** |
| * Returns the finite field <code>field</code> that this |
| * elliptic curve is over. |
| * @return the field <code>field</code> that this curve |
| * is over. |
| */ |
| public ECField getField() { |
| return field; |
| } |
| |
| /** |
| * Returns the first coefficient <code>a</code> of the |
| * elliptic curve. |
| * @return the first coefficient <code>a</code>. |
| */ |
| public BigInteger getA() { |
| return a; |
| } |
| |
| /** |
| * Returns the second coefficient <code>b</code> of the |
| * elliptic curve. |
| * @return the second coefficient <code>b</code>. |
| */ |
| public BigInteger getB() { |
| return b; |
| } |
| |
| /** |
| * Returns the seeding bytes <code>seed</code> used |
| * during curve generation. May be null if not specified. |
| * @return the seeding bytes <code>seed</code>. A new |
| * array is returned each time this method is called. |
| */ |
| public byte[] getSeed() { |
| if (seed == null) return null; |
| else return seed.clone(); |
| } |
| |
| /** |
| * Compares this elliptic curve for equality with the |
| * specified object. |
| * @param obj the object to be compared. |
| * @return true if <code>obj</code> is an instance of |
| * EllipticCurve and the field, A, and B match, false otherwise. |
| */ |
| public boolean equals(Object obj) { |
| if (this == obj) return true; |
| if (obj instanceof EllipticCurve) { |
| EllipticCurve curve = (EllipticCurve) obj; |
| if ((field.equals(curve.field)) && |
| (a.equals(curve.a)) && |
| (b.equals(curve.b))) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| /** |
| * Returns a hash code value for this elliptic curve. |
| * @return a hash code value computed from the hash codes of the field, A, |
| * and B, as follows: |
| * <code> |
| * (field.hashCode() << 6) + (a.hashCode() << 4) + (b.hashCode() << 2) |
| * </code> |
| */ |
| public int hashCode() { |
| return (field.hashCode() << 6 + |
| (a.hashCode() << 4) + |
| (b.hashCode() << 2)); |
| } |
| } |