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25 
26 package com.sun.crypto.provider;
27 
28 import javax.crypto.KeyGeneratorSpi;
29 import javax.crypto.SecretKey;
30 import javax.crypto.spec.DESedeKeySpec;
31 import java.security.SecureRandom;
32 import java.security.InvalidParameterException;
33 import java.security.InvalidAlgorithmParameterException;
34 import java.security.InvalidKeyException;
35 import java.security.spec.AlgorithmParameterSpec;
36 
37 /**
38  * This class generates a Triple DES key.
39  *
40  * @author Jan Luehe
41  *
42  */
43 
44 public final class DESedeKeyGenerator extends KeyGeneratorSpi {
45 
46     private SecureRandom random = null;
47     private int keysize = 168;
48 
49     /**
50      * Empty constructor
51      */
DESedeKeyGenerator()52     public DESedeKeyGenerator() {
53     }
54 
55     /**
56      * Initializes this key generator.
57      *
58      * @param random the source of randomness for this generator
59      */
engineInit(SecureRandom random)60     protected void engineInit(SecureRandom random) {
61         this.random = random;
62     }
63 
64     /**
65      * Initializes this key generator with the specified parameter
66      * set and a user-provided source of randomness.
67      *
68      * @param params the key generation parameters
69      * @param random the source of randomness for this key generator
70      *
71      * @exception InvalidAlgorithmParameterException if <code>params</code> is
72      * inappropriate for this key generator
73      */
engineInit(AlgorithmParameterSpec params, SecureRandom random)74     protected void engineInit(AlgorithmParameterSpec params,
75                               SecureRandom random)
76         throws InvalidAlgorithmParameterException {
77             throw new InvalidAlgorithmParameterException
78                 ("Triple DES key generation does not take any parameters");
79     }
80 
81     /**
82      * Initializes this key generator for a certain keysize, using the given
83      * source of randomness.
84      *
85      * @param keysize the keysize. This is an algorithm-specific
86      * metric specified in number of bits. A keysize with 112 bits of entropy
87      * corresponds to a Triple DES key with 2 intermediate keys, and a keysize
88      * with 168 bits of entropy corresponds to a Triple DES key with 3
89      * intermediate keys.
90      * @param random the source of randomness for this key generator
91      */
engineInit(int keysize, SecureRandom random)92     protected void engineInit(int keysize, SecureRandom random) {
93         if ((keysize != 112) && (keysize != 168)) {
94             throw new InvalidParameterException("Wrong keysize: must be "
95                                                 + "equal to 112 or 168");
96         }
97         this.keysize = keysize;
98         this.engineInit(random);
99     }
100 
101     /**
102      * Generates the Triple DES key.
103      *
104      * @return the new Triple DES key
105      */
engineGenerateKey()106     protected SecretKey engineGenerateKey() {
107         if (this.random == null) {
108             this.random = SunJCE.getRandom();
109         }
110 
111         byte[] rawkey = new byte[DESedeKeySpec.DES_EDE_KEY_LEN];
112 
113         if (keysize == 168) {
114             // 3 intermediate keys
115             this.random.nextBytes(rawkey);
116 
117             // Do parity adjustment for each intermediate key
118             DESKeyGenerator.setParityBit(rawkey, 0);
119             DESKeyGenerator.setParityBit(rawkey, 8);
120             DESKeyGenerator.setParityBit(rawkey, 16);
121         } else {
122             // 2 intermediate keys
123             byte[] tmpkey = new byte[16];
124             this.random.nextBytes(tmpkey);
125             DESKeyGenerator.setParityBit(tmpkey, 0);
126             DESKeyGenerator.setParityBit(tmpkey, 8);
127             System.arraycopy(tmpkey, 0, rawkey, 0, tmpkey.length);
128             // Copy the first 8 bytes into the last
129             System.arraycopy(tmpkey, 0, rawkey, 16, 8);
130             java.util.Arrays.fill(tmpkey, (byte)0x00);
131         }
132 
133         DESedeKey desEdeKey = null;
134         try {
135             desEdeKey = new DESedeKey(rawkey);
136         } catch (InvalidKeyException ike) {
137             // this never happens
138             throw new RuntimeException(ike.getMessage());
139         }
140 
141         java.util.Arrays.fill(rawkey, (byte)0x00);
142 
143         return desEdeKey;
144     }
145 }
146