gnu.java.security.prng

Interface IRandom

All Superinterfaces:: Cloneable

Known Implementing Classes:: ARCFour, BasePRNG, CSPRNG, Fortuna, Fortuna.Generator, ICMGenerator, MDGenerator, PBKDF2, UMacGenerator

public interface IRandom

extends Cloneable

The basic visible methods of any pseudo-random number generator.

The [HAC] defines a PRNG (as implemented in this library) as follows:

"5.6 Definition: A pseudorandom bit generator (PRBG) is said to pass the next-bit test if there is no polynomial-time algorithm which, on input of the first L bits of an output sequence S, can predict the (L+1)^st bit of S with a probability significantly greater than 1/2."
"5.8 Definition: A PRBG that passes the next-bit test (possibly under some plausible but unproved mathematical assumption such as the intractability of factoring integers) is called a cryptographically secure pseudorandom bit generator (CSPRBG)."

IMPLEMENTATION NOTE: Although all the concrete classes in this package implement the Cloneable interface, it is important to note here that such an operation, for those algorithms that use an underlying symmetric key block cipher, DOES NOT clone any session key material that may have been used in initialising the source PRNG (the instance to be cloned). Instead a clone of an already initialised PRNG, that uses an underlying symmetric key block cipher, is another instance with a clone of the same cipher that operates with the same block size but without any knowledge of neither key material nor key size.

References:

[HAC]: Handbook of Applied Cryptography.
CRC Press, Inc. ISBN 0-8493-8523-7, 1997
Menezes, A., van Oorschot, P. and S. Vanstone.

Method Summary
`void`	`addRandomByte(byte b)` Supplement, or possibly replace, the random state of this PRNG with a random byte.
`void`	`addRandomBytes(byte[] in)` Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.
`void`	`addRandomBytes(byte[] in, int offset, int length)` Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.
`Object`	`clone()` Returns a clone copy of this instance.
`void`	`init(Map<K,V> attributes)` Initialises the pseudo-random number generator scheme with the appropriate attributes.
`String`	`name()` Returns the canonical name of this instance.
`byte`	`nextByte()` Returns the next 8 bits of random data generated from this instance.
`void`	`nextBytes(byte[] out, int offset, int length)` Fills the designated byte array, starting from byte at index `offset`, for a maximum of `length` bytes with the output of this generator instance.

addRandomByte

public void addRandomByte(byte b)

Supplement, or possibly replace, the random state of this PRNG with a random byte.
Implementations are not required to implement this method in any meaningful way; this may be a no-operation, and implementations may throw an UnsupportedOperationException.
Parameters:
b - The byte to add.

addRandomBytes

public void addRandomBytes(byte[] in)

Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.
Implementations are not required to implement this method in any meaningful way; this may be a no-operation, and implementations may throw an UnsupportedOperationException.
Parameters:
in - The buffer of new random bytes to add.

addRandomBytes

public void addRandomBytes(byte[] in,
                           int offset,
                           int length)

Supplement, or possibly replace, the random state of this PRNG with a sequence of new random bytes.
Implementations are not required to implement this method in any meaningful way; this may be a no-operation, and implementations may throw an UnsupportedOperationException.
Parameters:
in - The buffer of new random bytes to add.
offset - The offset from whence to begin reading random bytes.
length - The number of random bytes to add.
Throws:
IndexOutOfBoundsException - If offset, length, or offset+length is out of bounds.

clone

public Object clone()
            throws CloneNotSupportedException

Returns a clone copy of this instance.
Overrides:
clone in interface Object
Returns:
a clone copy of this instance.

init

public void init(Map<K,V> attributes)

Initialises the pseudo-random number generator scheme with the appropriate attributes.
Parameters:
attributes - a set of name-value pairs that describe the desired future instance behaviour.
Throws:
IllegalArgumentException - if at least one of the defined name/ value pairs contains invalid data.

name

public String name()

Returns the canonical name of this instance.
Returns:
the canonical name of this instance.

nextByte

public byte nextByte()
            throws IllegalStateException,
                   LimitReachedException

Returns the next 8 bits of random data generated from this instance.
Returns:
the next 8 bits of random data generated from this instance.
Throws:
IllegalStateException - if the instance is not yet initialised.
LimitReachedException - if this instance has reached its theoretical limit for generating non-repetitive pseudo-random data.

nextBytes

public void nextBytes(byte[] out,
                      int offset,
                      int length)
            throws IllegalStateException,
                   LimitReachedException

Fills the designated byte array, starting from byte at index offset, for a maximum of length bytes with the output of this generator instance.
Parameters:
out - the placeholder to contain the generated random bytes.
offset - the starting index in out to consider. This method does nothing if this parameter is not within 0 and out.length.
length - the maximum number of required random bytes. This method does nothing if this parameter is less than 1.
Throws:
IllegalStateException - if the instance is not yet initialised.
LimitReachedException - if this instance has reached its theoretical limit for generating non-repetitive pseudo-random data.

IRandom.java -- Copyright (C) 2001, 2002, 2003, 2006 Free Software Foundation, Inc. This file is a part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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gnu.java.security.prng

Interface IRandom

Method Summary

Method Details

addRandomByte

addRandomBytes

addRandomBytes

clone

init

name

nextByte

nextBytes