Class AESCounterRNG

java.lang.Object
java.util.Random
org.uncommons.maths.random.AESCounterRNG
All Implemented Interfaces:
Serializable, RandomGenerator, 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

See Also:
  • Field Details

    • DEFAULT_SEED_SIZE_BYTES

      private static final int DEFAULT_SEED_SIZE_BYTES
      See Also:
    • seed

      private final byte[] seed
    • cipher

      private final Cipher cipher
    • counter

      private final byte[] counter
    • lock

      private final ReentrantLock lock
    • currentBlock

      private byte[] currentBlock
    • index

      private int index
  • Constructor Details

    • 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 Details

    • getSeed

      public byte[] getSeed()
      Specified by:
      getSeed in interface RepeatableRNG
      Returns:
      The seed data used to initialise this pseudo-random number generator.
    • incrementCounter

      private void incrementCounter()
    • nextBlock

      private byte[] nextBlock() throws GeneralSecurityException
      Generates a single 128-bit block (16 bytes).
      Returns:
      A 16-byte block of random data.
      Throws:
      GeneralSecurityException - If there is a problem with the cipher that generates the random data.
    • next

      protected final int next(int bits)
      Overrides:
      next in class Random