Imported GNU Classpath 0.90
[official-gcc.git] / libjava / classpath / gnu / java / security / prng / IRandom.java
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1 /* IRandom.java --
2 Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc.
4 This file is a part of GNU Classpath.
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21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
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27 permission to link this library with independent modules to produce an
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31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
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34 this exception to your version of the library, but you are not
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36 exception statement from your version. */
39 package gnu.java.security.prng;
41 import java.util.Map;
43 /**
44 * <p>The basic visible methods of any pseudo-random number generator.</p>
46 * <p>The [HAC] defines a PRNG (as implemented in this library) as follows:</p>
48 * <ul>
49 * <li>"5.6 Definition: A pseudorandom bit generator (PRBG) is said to pass
50 * the <em>next-bit test</em> if there is no polynomial-time algorithm which,
51 * on input of the first <code>L</code> bits of an output sequence <code>S</code>,
52 * can predict the <code>(L+1)</code>st bit of <code>S</code> with a
53 * probability significantly grater than <code>1/2</code>."</li>
55 * <li>"5.8 Definition: A PRBG that passes the <em>next-bit test</em>
56 * (possibly under some plausible but unproved mathematical assumption such
57 * as the intractability of factoring integers) is called a
58 * <em>cryptographically secure pseudorandom bit generator</em> (CSPRBG)."</li>
59 * </ul>
61 * <p><b>IMPLEMENTATION NOTE</b>: Although all the concrete classes in this
62 * package implement the {@link Cloneable} interface, it is important to note
63 * here that such an operation, for those algorithms that use an underlting
64 * symmetric key block cipher, <b>DOES NOT</b> clone any session key material
65 * that may have been used in initialising the source PRNG (the instance to be
66 * cloned). Instead a clone of an already initialised PRNG, that uses and
67 * underlying symmetric key block cipher, is another instance with a clone of
68 * the same cipher that operates with the <b>same block size</b> but without any
69 * knowledge of neither key material nor key size.</p>
71 * <p>References:</p>
73 * <ol>
74 * <li><a href="http://www.cacr.math.uwaterloo.ca/hac">[HAC]</a>: Handbook of
75 * Applied Cryptography.<br>
76 * CRC Press, Inc. ISBN 0-8493-8523-7, 1997<br>
77 * Menezes, A., van Oorschot, P. and S. Vanstone.</li>
78 * </ol>
80 public interface IRandom extends Cloneable
83 // Constants
84 // -------------------------------------------------------------------------
86 // Methods
87 // -------------------------------------------------------------------------
89 /**
90 * <p>Returns the canonical name of this instance.</p>
92 * @return the canonical name of this instance. */
93 String name();
95 /**
96 * <p>Initialises the pseudo-random number generator scheme with the
97 * appropriate attributes.</p>
99 * @param attributes a set of name-value pairs that describe the desired
100 * future instance behaviour.
101 * @exception IllegalArgumentException if at least one of the defined name/
102 * value pairs contains invalid data.
104 void init(Map attributes);
107 * <p>Returns the next 8 bits of random data generated from this instance.</p>
109 * @return the next 8 bits of random data generated from this instance.
110 * @exception IllegalStateException if the instance is not yet initialised.
111 * @exception LimitReachedException if this instance has reached its
112 * theoretical limit for generating non-repetitive pseudo-random data.
114 byte nextByte() throws IllegalStateException, LimitReachedException;
117 * <p>Fills the designated byte array, starting from byte at index
118 * <code>offset</code>, for a maximum of <code>length</code> bytes with the
119 * output of this generator instance.
121 * @param out the placeholder to contain the generated random bytes.
122 * @param offset the starting index in <i>out</i> to consider. This method
123 * does nothing if this parameter is not within <code>0</code> and
124 * <code>out.length</code>.
125 * @param length the maximum number of required random bytes. This method
126 * does nothing if this parameter is less than <code>1</code>.
127 * @exception IllegalStateException if the instance is not yet initialised.
128 * @exception LimitReachedException if this instance has reached its
129 * theoretical limit for generating non-repetitive pseudo-random data.
131 void nextBytes(byte[] out, int offset, int length)
132 throws IllegalStateException, LimitReachedException;
135 * <p>Supplement, or possibly replace, the random state of this PRNG with
136 * a random byte.</p>
138 * <p>Implementations are not required to implement this method in any
139 * meaningful way; this may be a no-operation, and implementations may
140 * throw an {@link UnsupportedOperationException}.</p>
142 * @param b The byte to add.
144 void addRandomByte(byte b);
147 * <p>Supplement, or possibly replace, the random state of this PRNG with
148 * a sequence of new random bytes.</p>
150 * <p>Implementations are not required to implement this method in any
151 * meaningful way; this may be a no-operation, and implementations may
152 * throw an {@link UnsupportedOperationException}.</p>
154 * @param in The buffer of new random bytes to add.
156 void addRandomBytes(byte[] in);
159 * <p>Supplement, or possibly replace, the random state of this PRNG with
160 * a sequence of new random bytes.</p>
162 * <p>Implementations are not required to implement this method in any
163 * meaningful way; this may be a no-operation, and implementations may
164 * throw an {@link UnsupportedOperationException}.</p>
166 * @param in The buffer of new random bytes to add.
167 * @param offset The offset from whence to begin reading random bytes.
168 * @param length The number of random bytes to add.
169 * @exception IndexOutOfBoundsException If <i>offset</i>, <i>length</i>,
170 * or <i>offset</i>+<i>length</i> is out of bounds.
172 void addRandomBytes(byte[] in, int offset, int length);
175 * <p>Returns a clone copy of this instance.</p>
177 * @return a clone copy of this instance.
179 Object clone() throws CloneNotSupportedException;