001: /*
002: *
003: *
004: * Copyright 1990-2007 Sun Microsystems, Inc. All Rights Reserved.
005: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
006: *
007: * This program is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU General Public License version
009: * 2 only, as published by the Free Software Foundation.
010: *
011: * This program is distributed in the hope that it will be useful, but
012: * WITHOUT ANY WARRANTY; without even the implied warranty of
013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014: * General Public License version 2 for more details (a copy is
015: * included at /legal/license.txt).
016: *
017: * You should have received a copy of the GNU General Public License
018: * version 2 along with this work; if not, write to the Free Software
019: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
020: * 02110-1301 USA
021: *
022: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
023: * Clara, CA 95054 or visit www.sun.com if you need additional
024: * information or have any questions.
025: */
026:
027: package com.sun.midp.crypto;
028:
029: /**
030: * This MessageDigest class provides applications the functionality of a
031: * message digest algorithm, such as MD5 or SHA.
032: * Message digests are secure one-way hash functions that take arbitrary-sized
033: * data and output a fixed-length hash value.
034: *
035: * <p>A <code>MessageDigest</code> object starts out initialized. The data is
036: * processed through it using the <code>update</code>
037: * method. At any point {@link #reset() reset} can be called
038: * to reset the digest. Once all the data to be updated has been
039: * updated, the <code>digest</code> method should
040: * be called to complete the hash computation.
041: *
042: * <p>The <code>digest</code> method can be called once for a given number
043: * of updates. After <code>digest</code> has been called,
044: * the <code>MessageDigest</code>
045: * object is reset to its initialized state.
046: */
047: public abstract class MessageDigest {
048: /** Protected constructor. */
049: protected MessageDigest() {
050: }
051:
052: /**
053: * Generates a <code>MessageDigest</code> object that implements
054: * the specified digest
055: * algorithm.
056: *
057: * @param algorithm the name of the algorithm requested.
058: * See Appendix A in the
059: * Java Cryptography Architecture API Specification & Reference
060: * for information about standard algorithm names.
061: *
062: * @return a MessageDigest object implementing the specified
063: * algorithm.
064: *
065: * @exception NoSuchAlgorithmException if the algorithm is
066: * not available in the caller's environment.
067: */
068: public static MessageDigest getInstance(String algorithm)
069: throws NoSuchAlgorithmException {
070:
071: if (algorithm == null || algorithm.length() == 0) {
072: throw new IllegalArgumentException();
073: }
074:
075: algorithm = algorithm.toUpperCase();
076:
077: if (algorithm.equals("MD2")) {
078: return new MD2();
079: } else if (algorithm.equals("MD5")) {
080: return new MD5();
081: } else if (algorithm.equals("SHA-1")) {
082: return new SHA();
083: }
084:
085: throw new NoSuchAlgorithmException(algorithm);
086: }
087:
088: /**
089: * Gets the message digest algorithm.
090: * @return algorithm implemented by this MessageDigest object
091: */
092: public abstract String getAlgorithm();
093:
094: /**
095: * Gets the length (in bytes) of the hash.
096: * @return byte-length of the hash produced by this object
097: */
098: public abstract int getDigestLength();
099:
100: /**
101: * Accumulates a hash of the input data. This method is useful when
102: * the input data to be hashed is not available in one byte array.
103: * @param inBuf input buffer of data to be hashed
104: * @param inOff offset within inBuf where input data begins
105: * @param inLen length (in bytes) of data to be hashed
106: * @see #doFinal(byte[], int, int, byte[], int)
107: */
108: public abstract void update(byte[] inBuf, int inOff, int inLen);
109:
110: /**
111: * Completes the hash computation by performing final operations
112: * such as padding. The digest is reset after this call is made.
113: *
114: * @param buf output buffer for the computed digest
115: *
116: * @param offset offset into the output buffer to begin storing the digest
117: *
118: * @param len number of bytes within buf allotted for the digest
119: *
120: * @return the number of bytes placed into <code>buf</code>
121: *
122: * @exception DigestException if an error occurs.
123: */
124: public abstract int digest(byte[] buf, int offset, int len)
125: throws DigestException;
126:
127: /**
128: * Resets the MessageDigest to the initial state for further use.
129: */
130: public abstract void reset();
131:
132: /**
133: * Clones the MessageDigest object.
134: * @return a clone of this object
135: */
136: public abstract Object clone();
137: }
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