1 /*
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package com.sun.crypto.provider;
27
28 import java.math.BigInteger;
29 import java.security.*;
30 import java.security.spec.AlgorithmParameterSpec;
31 import java.security.spec.InvalidParameterSpecException;
32 import javax.crypto.spec.DHParameterSpec;
33 import javax.crypto.spec.DHGenParameterSpec;
34
35 import sun.security.provider.ParameterCache;
36
37 /**
38 * This class represents the key pair generator for Diffie-Hellman key pairs.
39 *
40 * <p>This key pair generator may be initialized in two different ways:
41 *
42 * <ul>
43 * <li>By providing the size in bits of the prime modulus -
44 * This will be used to create a prime modulus and base generator, which will
45 * then be used to create the Diffie-Hellman key pair. The default size of the
46 * prime modulus is 1024 bits.
47 * <li>By providing a prime modulus and base generator
48 * </ul>
49 *
50 * @author Jan Luehe
51 *
52 *
53 * @see java.security.KeyPairGenerator
54 */
55 public final class DHKeyPairGenerator extends KeyPairGeneratorSpi {
56
57 // parameters to use or null if not specified
58 private DHParameterSpec params;
59
60 // The size in bits of the prime modulus
61 private int pSize;
62
63 // The size in bits of the random exponent (private value)
64 private int lSize;
65
66 // The source of randomness
67 private SecureRandom random;
68
69 public DHKeyPairGenerator() {
70 super();
71 initialize(1024, null);
72 }
73
74 private static void checkKeySize(int keysize)
75 throws InvalidParameterException {
76
77 if ((keysize < 512) || (keysize > 2048) || ((keysize & 0x3F) != 0)) {
78 throw new InvalidParameterException(
79 "DH key size must be multiple of 64, and can only range " +
80 "from 512 to 2048 (inclusive). " +
81 "The specific key size " + keysize + " is not supported");
82 }
83 }
84
85 /**
86 * Initializes this key pair generator for a certain keysize and source of
87 * randomness.
88 * The keysize is specified as the size in bits of the prime modulus.
89 *
90 * @param keysize the keysize (size of prime modulus) in bits
91 * @param random the source of randomness
92 */
93 public void initialize(int keysize, SecureRandom random) {
94 checkKeySize(keysize);
95
96 this.pSize = keysize;
97 this.lSize = 0;
98 this.random = random;
99 this.params = null;
100 }
101
102 /**
103 * Initializes this key pair generator for the specified parameter
104 * set and source of randomness.
105 *
106 * <p>The given parameter set contains the prime modulus, the base
107 * generator, and optionally the requested size in bits of the random
108 * exponent (private value).
109 *
110 * @param params the parameter set used to generate the key pair
111 * @param random the source of randomness
112 *
113 * @exception InvalidAlgorithmParameterException if the given parameters
114 * are inappropriate for this key pair generator
115 */
116 public void initialize(AlgorithmParameterSpec algParams,
117 SecureRandom random) throws InvalidAlgorithmParameterException {
118 if (!(algParams instanceof DHParameterSpec)){
119 throw new InvalidAlgorithmParameterException
120 ("Inappropriate parameter type");
121 }
122
123 params = (DHParameterSpec)algParams;
124 pSize = params.getP().bitLength();
125 try {
126 checkKeySize(pSize);
127 } catch (InvalidParameterException ipe) {
128 throw new InvalidAlgorithmParameterException(ipe.getMessage());
129 }
130
131 // exponent size is optional, could be 0
132 lSize = params.getL();
133
134 // Require exponentSize < primeSize
135 if ((lSize != 0) && (lSize > pSize)) {
136 throw new InvalidAlgorithmParameterException
137 ("Exponent size must not be larger than modulus size");
138 }
139 this.random = random;
140 }
141
142 /**
143 * Generates a key pair.
144 *
145 * @return the new key pair
146 */
147 public KeyPair generateKeyPair() {
148 if (random == null) {
149 random = SunJCE.getRandom();
150 }
151
152 if (params == null) {
153 try {
154 params = ParameterCache.getDHParameterSpec(pSize, random);
155 } catch (GeneralSecurityException e) {
156 // should never happen
157 throw new ProviderException(e);
158 }
159 }
160
161 BigInteger p = params.getP();
162 BigInteger g = params.getG();
163
164 if (lSize <= 0) {
165 lSize = pSize >> 1;
166 // use an exponent size of (pSize / 2) but at least 384 bits
167 if (lSize < 384) {
168 lSize = 384;
169 }
170 }
171
172 BigInteger x;
173 BigInteger pMinus2 = p.subtract(BigInteger.valueOf(2));
174
175 //
176 // PKCS#3 section 7.1 "Private-value generation"
177 // Repeat if either of the followings does not hold:
178 // 0 < x < p-1
179 // 2^(lSize-1) <= x < 2^(lSize)
180 //
181 do {
182 // generate random x up to 2^lSize bits long
183 x = new BigInteger(lSize, random);
184 } while ((x.compareTo(BigInteger.ONE) < 0) ||
185 ((x.compareTo(pMinus2) > 0)) || (x.bitLength() != lSize));
186
187 // calculate public value y
188 BigInteger y = g.modPow(x, p);
189
190 DHPublicKey pubKey = new DHPublicKey(y, p, g, lSize);
191 DHPrivateKey privKey = new DHPrivateKey(x, p, g, lSize);
192 return new KeyPair(pubKey, privKey);
193 }
194 }