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.security.*;
29 import java.security.spec.*;
30 import javax.crypto.spec.DHParameterSpec;
31 import javax.crypto.spec.DHGenParameterSpec;
32
33 /*
34 * This class generates parameters for the Diffie-Hellman algorithm.
35 * The parameters are a prime, a base, and optionally the length in bits of
36 * the private value.
37 *
38 * <p>The Diffie-Hellman parameter generation accepts the size in bits of the
39 * prime modulus and the size in bits of the random exponent as input.
40 * The size of the prime modulus defaults to 1024 bits.
41 *
42 * @author Jan Luehe
43 *
44 *
45 * @see java.security.AlgorithmParameters
46 * @see java.security.spec.AlgorithmParameterSpec
47 * @see DHParameters
48 */
49 public final class DHParameterGenerator
50 extends AlgorithmParameterGeneratorSpi {
51
52 // The size in bits of the prime modulus
53 private int primeSize = 1024;
54
55 // The size in bits of the random exponent (private value)
56 private int exponentSize = 0;
57
58 // The source of randomness
59 private SecureRandom random = null;
60
61 private static void checkKeySize(int keysize)
62 throws InvalidParameterException {
63 if ((keysize != 2048) &&
64 ((keysize < 512) || (keysize > 1024) || (keysize % 64 != 0))) {
65 throw new InvalidParameterException(
66 "DH key size must be multiple of 64 and range " +
67 "from 512 to 1024 (inclusive), or 2048. " +
68 "The specific key size " + keysize + " is not supported");
69 }
70 }
71
72 /**
73 * Initializes this parameter generator for a certain keysize
74 * and source of randomness.
75 * The keysize is specified as the size in bits of the prime modulus.
76 *
77 * @param keysize the keysize (size of prime modulus) in bits
78 * @param random the source of randomness
79 */
80 protected void engineInit(int keysize, SecureRandom random) {
81 // Re-uses DSA parameters and thus have the same range
82 checkKeySize(keysize);
83 this.primeSize = keysize;
84 this.random = random;
85 }
86
87 /**
88 * Initializes this parameter generator with a set of parameter
89 * generation values, which specify the size of the prime modulus and
90 * the size of the random exponent, both in bits.
91 *
92 * @param params the set of parameter generation values
93 * @param random the source of randomness
94 *
95 * @exception InvalidAlgorithmParameterException if the given parameter
96 * generation values are inappropriate for this parameter generator
97 */
98 protected void engineInit(AlgorithmParameterSpec genParamSpec,
99 SecureRandom random)
100 throws InvalidAlgorithmParameterException {
101 if (!(genParamSpec instanceof DHGenParameterSpec)) {
102 throw new InvalidAlgorithmParameterException
103 ("Inappropriate parameter type");
104 }
105
106 DHGenParameterSpec dhParamSpec = (DHGenParameterSpec)genParamSpec;
107
108 primeSize = dhParamSpec.getPrimeSize();
109
110 // Re-uses DSA parameters and thus have the same range
111 try {
112 checkKeySize(primeSize);
113 } catch (InvalidParameterException ipe) {
114 throw new InvalidAlgorithmParameterException(ipe.getMessage());
115 }
116
117 exponentSize = dhParamSpec.getExponentSize();
118 if (exponentSize <= 0) {
119 throw new InvalidAlgorithmParameterException
120 ("Exponent size must be greater than zero");
121 }
122
123 // Require exponentSize < primeSize
124 if (exponentSize >= primeSize) {
125 throw new InvalidAlgorithmParameterException
126 ("Exponent size must be less than modulus size");
127 }
128 }
129
130 /**
131 * Generates the parameters.
132 *
133 * @return the new AlgorithmParameters object
134 */
135 protected AlgorithmParameters engineGenerateParameters() {
136 AlgorithmParameters algParams = null;
137
138 if (this.exponentSize == 0) {
139 this.exponentSize = this.primeSize - 1;
140 }
141
142 if (this.random == null)
143 this.random = SunJCE.getRandom();
144
145 try {
146 AlgorithmParameterGenerator paramGen;
147 DSAParameterSpec dsaParamSpec;
148
149 paramGen = AlgorithmParameterGenerator.getInstance("DSA");
150 paramGen.init(this.primeSize, random);
151 algParams = paramGen.generateParameters();
152 dsaParamSpec = algParams.getParameterSpec(DSAParameterSpec.class);
153
154 DHParameterSpec dhParamSpec;
155 if (this.exponentSize > 0) {
156 dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),
157 dsaParamSpec.getG(),
158 this.exponentSize);
159 } else {
160 dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),
161 dsaParamSpec.getG());
162 }
163 algParams = AlgorithmParameters.getInstance("DH",
164 SunJCE.getInstance());
165 algParams.init(dhParamSpec);
166 } catch (InvalidParameterSpecException e) {
167 // this should never happen
168 throw new RuntimeException(e.getMessage());
169 } catch (NoSuchAlgorithmException e) {
170 // this should never happen, because we provide it
171 throw new RuntimeException(e.getMessage());
172 }
173 return algParams;
174 }
175 }