org.uncommons.maths.random
Class AESCounterRNG

java.lang.Object
  java.util.Random
      org.uncommons.maths.random.AESCounterRNG

All Implemented Interfaces:

Serializable, RepeatableRNG

public class AESCounterRNG
extends Random
implements RepeatableRNG

Non-linear random number generator based on the AES block cipher in counter mode. Uses the seed as a key to encrypt a 128-bit counter using AES(Rijndael).

By default, we only use a 128-bit key for the cipher because any larger key requires the inconvenience of installing the unlimited strength cryptography policy files for the Java platform. Larger keys may be used (192 or 256 bits) but if the cryptography policy files are not installed, a GeneralSecurityException will be thrown.

NOTE: Because instances of this class require 128-bit seeds, it is not possible to seed this RNG using the Random.setSeed(long) method inherited from Random. Calls to this method will have no effect. Instead the seed must be set by a constructor.

NOTE: THIS CLASS IS NOT SERIALIZABLE

Author:

Daniel Dyer

See Also:

Serialized Form

Constructor Summary

AESCounterRNG()
Creates a new RNG and seeds it using 128 bits from the default seeding strategy.

AESCounterRNG(byte[] seed)
Creates an RNG and seeds it with the specified seed data.

AESCounterRNG(int seedSizeBytes)
Seed the RNG using the default seed generation strategy to create a seed of the specified size.

AESCounterRNG(SeedGenerator seedGenerator)
Seed the RNG using the provided seed generation strategy to create a 128-bit seed.

Method Summary

byte[]	getSeed()
protected int	next(int bits)

Methods inherited from class java.util.Random

nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong, setSeed

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AESCounterRNG

public AESCounterRNG()
              throws GeneralSecurityException

Creates a new RNG and seeds it using 128 bits from the default seeding strategy.

Throws:

GeneralSecurityException - If there is a problem initialising the AES cipher.

AESCounterRNG

public AESCounterRNG(SeedGenerator seedGenerator)
              throws SeedException,
                     GeneralSecurityException

Seed the RNG using the provided seed generation strategy to create a 128-bit seed.

Parameters:

seedGenerator - The seed generation strategy that will provide the seed value for this RNG.

Throws:

SeedException - If there is a problem generating a seed.

GeneralSecurityException - If there is a problem initialising the AES cipher.

AESCounterRNG

public AESCounterRNG(int seedSizeBytes)
              throws GeneralSecurityException

Seed the RNG using the default seed generation strategy to create a seed of the specified size.

Parameters:

seedSizeBytes - The number of bytes to use for seed data. Valid values are 16 (128 bits), 24 (192 bits) and 32 (256 bits). Any other values will result in an exception from the AES implementation.

Throws:

GeneralSecurityException - If there is a problem initialising the AES cipher.

Since:

1.0.2

AESCounterRNG

public AESCounterRNG(byte[] seed)
              throws GeneralSecurityException

Creates an RNG and seeds it with the specified seed data.

Parameters:

seed - The seed data used to initialise the RNG.

Throws:

GeneralSecurityException - If there is a problem initialising the AES cipher.

Method Detail

getSeed

public byte[] getSeed()

Specified by:

getSeed in interface RepeatableRNG

Returns:

The seed data used to initialise this pseudo-random number generator.

next

protected final int next(int bits)

Overrides:

next in class Random