1 /*
2 * Copyright (c) 1997, 2007, 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 javax.crypto;
27
28 import java.security;
29 import java.security.spec;
30
31 /**
32 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
33 * for the <code>KeyAgreement</code> class.
34 * All the abstract methods in this class must be implemented by each
35 * cryptographic service provider who wishes to supply the implementation
36 * of a particular key agreement algorithm.
37 *
38 * <p> The keys involved in establishing a shared secret are created by one
39 * of the
40 * key generators (<code>KeyPairGenerator</code> or
41 * <code>KeyGenerator</code>), a <code>KeyFactory</code>, or as a result from
42 * an intermediate phase of the key agreement protocol
43 * ({@link #engineDoPhase(java.security.Key, boolean) engineDoPhase}).
44 *
45 * <p> For each of the correspondents in the key exchange,
46 * <code>engineDoPhase</code>
47 * needs to be called. For example, if the key exchange is with one other
48 * party, <code>engineDoPhase</code> needs to be called once, with the
49 * <code>lastPhase</code> flag set to <code>true</code>.
50 * If the key exchange is
51 * with two other parties, <code>engineDoPhase</code> needs to be called twice,
52 * the first time setting the <code>lastPhase</code> flag to
53 * <code>false</code>, and the second time setting it to <code>true</code>.
54 * There may be any number of parties involved in a key exchange.
55 *
56 * @author Jan Luehe
57 *
58 * @see KeyGenerator
59 * @see SecretKey
60 * @since 1.4
61 */
62
63 public abstract class KeyAgreementSpi {
64
65 /**
66 * Initializes this key agreement with the given key and source of
67 * randomness. The given key is required to contain all the algorithm
68 * parameters required for this key agreement.
69 *
70 * <p> If the key agreement algorithm requires random bytes, it gets them
71 * from the given source of randomness, <code>random</code>.
72 * However, if the underlying
73 * algorithm implementation does not require any random bytes,
74 * <code>random</code> is ignored.
75 *
76 * @param key the party's private information. For example, in the case
77 * of the Diffie-Hellman key agreement, this would be the party's own
78 * Diffie-Hellman private key.
79 * @param random the source of randomness
80 *
81 * @exception InvalidKeyException if the given key is
82 * inappropriate for this key agreement, e.g., is of the wrong type or
83 * has an incompatible algorithm type.
84 */
85 protected abstract void engineInit(Key key, SecureRandom random)
86 throws InvalidKeyException;
87
88 /**
89 * Initializes this key agreement with the given key, set of
90 * algorithm parameters, and source of randomness.
91 *
92 * @param key the party's private information. For example, in the case
93 * of the Diffie-Hellman key agreement, this would be the party's own
94 * Diffie-Hellman private key.
95 * @param params the key agreement parameters
96 * @param random the source of randomness
97 *
98 * @exception InvalidKeyException if the given key is
99 * inappropriate for this key agreement, e.g., is of the wrong type or
100 * has an incompatible algorithm type.
101 * @exception InvalidAlgorithmParameterException if the given parameters
102 * are inappropriate for this key agreement.
103 */
104 protected abstract void engineInit(Key key, AlgorithmParameterSpec params,
105 SecureRandom random)
106 throws InvalidKeyException, InvalidAlgorithmParameterException;
107
108 /**
109 * Executes the next phase of this key agreement with the given
110 * key that was received from one of the other parties involved in this key
111 * agreement.
112 *
113 * @param key the key for this phase. For example, in the case of
114 * Diffie-Hellman between 2 parties, this would be the other party's
115 * Diffie-Hellman public key.
116 * @param lastPhase flag which indicates whether or not this is the last
117 * phase of this key agreement.
118 *
119 * @return the (intermediate) key resulting from this phase, or null if
120 * this phase does not yield a key
121 *
122 * @exception InvalidKeyException if the given key is inappropriate for
123 * this phase.
124 * @exception IllegalStateException if this key agreement has not been
125 * initialized.
126 */
127 protected abstract Key engineDoPhase(Key key, boolean lastPhase)
128 throws InvalidKeyException, IllegalStateException;
129
130 /**
131 * Generates the shared secret and returns it in a new buffer.
132 *
133 * <p>This method resets this <code>KeyAgreementSpi</code> object,
134 * so that it
135 * can be reused for further key agreements. Unless this key agreement is
136 * reinitialized with one of the <code>engineInit</code> methods, the same
137 * private information and algorithm parameters will be used for
138 * subsequent key agreements.
139 *
140 * @return the new buffer with the shared secret
141 *
142 * @exception IllegalStateException if this key agreement has not been
143 * completed yet
144 */
145 protected abstract byte[] engineGenerateSecret()
146 throws IllegalStateException;
147
148 /**
149 * Generates the shared secret, and places it into the buffer
150 * <code>sharedSecret</code>, beginning at <code>offset</code> inclusive.
151 *
152 * <p>If the <code>sharedSecret</code> buffer is too small to hold the
153 * result, a <code>ShortBufferException</code> is thrown.
154 * In this case, this call should be repeated with a larger output buffer.
155 *
156 * <p>This method resets this <code>KeyAgreementSpi</code> object,
157 * so that it
158 * can be reused for further key agreements. Unless this key agreement is
159 * reinitialized with one of the <code>engineInit</code> methods, the same
160 * private information and algorithm parameters will be used for
161 * subsequent key agreements.
162 *
163 * @param sharedSecret the buffer for the shared secret
164 * @param offset the offset in <code>sharedSecret</code> where the
165 * shared secret will be stored
166 *
167 * @return the number of bytes placed into <code>sharedSecret</code>
168 *
169 * @exception IllegalStateException if this key agreement has not been
170 * completed yet
171 * @exception ShortBufferException if the given output buffer is too small
172 * to hold the secret
173 */
174 protected abstract int engineGenerateSecret(byte[] sharedSecret,
175 int offset)
176 throws IllegalStateException, ShortBufferException;
177
178 /**
179 * Creates the shared secret and returns it as a secret key object
180 * of the requested algorithm type.
181 *
182 * <p>This method resets this <code>KeyAgreementSpi</code> object,
183 * so that it
184 * can be reused for further key agreements. Unless this key agreement is
185 * reinitialized with one of the <code>engineInit</code> methods, the same
186 * private information and algorithm parameters will be used for
187 * subsequent key agreements.
188 *
189 * @param algorithm the requested secret key algorithm
190 *
191 * @return the shared secret key
192 *
193 * @exception IllegalStateException if this key agreement has not been
194 * completed yet
195 * @exception NoSuchAlgorithmException if the requested secret key
196 * algorithm is not available
197 * @exception InvalidKeyException if the shared secret key material cannot
198 * be used to generate a secret key of the requested algorithm type (e.g.,
199 * the key material is too short)
200 */
201 protected abstract SecretKey engineGenerateSecret(String algorithm)
202 throws IllegalStateException, NoSuchAlgorithmException,
203 InvalidKeyException;
204 }