umontreal.iro.lecuyer.rng

Class RandRijndael

java.lang.Object

umontreal.iro.lecuyer.rng.RandomStreamBase

umontreal.iro.lecuyer.rng.RandRijndael

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, CloneableRandomStream, RandomStream

public class RandRijndael
extends RandomStreamBase

Implements a RNG using the Rijndael block cipher algorithm (AES) with key and block lengths of 128 bits. A block of 128 bits is encrypted by the Rijndael algorithm to generate 128 pseudo-random bits. Those bits are split into four words of 32 bits which are returned successively by the method nextValue. The unencrypted block is the state of the generator. It is incremented by 1 at every four calls to nextValue. Thus, the period is 2¹³⁰ and jumping ahead is easy. The values of V, W and Z are 2⁴⁰, 2⁴² and 2⁸², respectively (see RandomStream for their definition). Seeds/states must be given as 16-dimensional vectors of bytes (8-bit integers). The default initial seed is a vector filled with zeros.

The Rijndael implementation used here is that of the Cryptix Development Team, which can be found on the Rijndael creators' page .

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
RandRijndael() Constructs a new stream.
RandRijndael(java.lang.String name) Constructs a new stream with the identifier name (used in the toString method).

Method Summary

Modifier and Type	Method and Description
RandRijndael	clone() Clones the current generator and return its copy.
byte[]	getState() Returns the current state of the stream, represented as an array of four integers.
void	resetNextSubstream() Reinitializes the stream to the beginning of its next substream: Ng is computed, and Cg and Bg are set to Ng.
void	resetStartStream() Reinitializes the stream to its initial state Ig: Cg and Bg are set to Ig.
void	resetStartSubstream() Reinitializes the stream to the beginning of its current substream: Cg is set to Bg.
static void	setPackageSeed(byte[] seed) Sets the initial seed for the class RandRijndael to the 16 bytes of the vector seed[0..15].
void	setSeed(byte[] seed) This method is discouraged for normal use.
java.lang.String	toString() Returns a string containing the current state of this stream.

Methods inherited from class umontreal.iro.lecuyer.rng.RandomStreamBase

formatState, formatStateFull, increasedPrecision, nextArrayOfDouble, nextArrayOfInt, nextDouble, nextInt

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

RandRijndael

public RandRijndael()

Constructs a new stream.

RandRijndael

public RandRijndael(java.lang.String name)

Constructs a new stream with the identifier name (used in the toString method).

Parameters:

name - name of the stream

Method Detail

setPackageSeed

public static void setPackageSeed(byte[] seed)

Sets the initial seed for the class RandRijndael to the 16 bytes of the vector seed[0..15]. This will be the initial state (or seed) of the next created stream. The default seed for the first stream is (0, 0,…, 0, 0).

Parameters:

seed - array of 16 elements representing the seed

setSeed

public void setSeed(byte[] seed)

This method is discouraged for normal use. Initializes the stream at the beginning of a stream with the initial seed seed[0..15]. This method only affects the specified stream; the others are not modified, so the beginning of the streams will not be spaced Z values apart. For this reason, this method should only be used in very exceptional cases; proper use of the reset... methods and of the stream constructor is preferable.

Parameters:

seed - array of 16 elements representing the seed

getState

public byte[] getState()

Returns the current state of the stream, represented as an array of four integers. It should be noted that each state of this generator returns 4 successive values. The particular value of these 4 which will be returned next is not given by this method.

Returns:

the current state of the stream

clone

public RandRijndael clone()

Clones the current generator and return its copy.

Specified by:

clone in interface CloneableRandomStream

Overrides:

clone in class RandomStreamBase

Returns:

A deep copy of the current generator

resetStartStream

public void resetStartStream()

Description copied from interface: RandomStream

Reinitializes the stream to its initial state I_g: C_g and B_g are set to I_g.

Specified by:

resetStartStream in interface RandomStream

Specified by:

resetStartStream in class RandomStreamBase

resetStartSubstream

public void resetStartSubstream()

Description copied from interface: RandomStream

Reinitializes the stream to the beginning of its current substream: C_g is set to B_g.

Specified by:

resetStartSubstream in interface RandomStream

Specified by:

resetStartSubstream in class RandomStreamBase

resetNextSubstream

public void resetNextSubstream()

Description copied from interface: RandomStream

Reinitializes the stream to the beginning of its next substream: N_g is computed, and C_g and B_g are set to N_g.

Specified by:

resetNextSubstream in interface RandomStream

Specified by:

resetNextSubstream in class RandomStreamBase

toString

public java.lang.String toString()

Description copied from interface: RandomStream

Returns a string containing the current state of this stream.

Specified by:

toString in interface RandomStream

Specified by:

toString in class RandomStreamBase

Returns:

the state of the generator formated as a string