Package io.github.pr0methean.betterrandom.seed

Class SecureRandomSeedGenerator

java.lang.Object

io.github.pr0methean.betterrandom.seed.SecureRandomSeedGenerator

All Implemented Interfaces:

SeedGenerator, Serializable

public class SecureRandomSeedGenerator
extends Object
implements SeedGenerator, Serializable

SeedGenerator implementation that uses Java's bundled SecureRandom RNG to generate random seed data.

The advantage of using SecureRandom for seeding but not as the primary RNG is that we can use it to seed RNGs that are much faster than SecureRandom.

This is the only seeding strategy that is guaranteed to work on all platforms and therefore is provided as a fall-back option should none of the other provided SeedGenerator implementations be usable.

On Oracle and OpenJDK, SecureRandom uses sun.security.provider.SeedGenerator; when /dev/random isn't available, that SeedGenerator class in turn uses the timing of newly-launched threads as a source of randomness, relying on the unpredictable interactions between different configurations of hardware and software and their workloads.

Author:

Daniel Dyer

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
static SecureRandomSeedGenerator	DEFAULT_INSTANCE	The default instance.

Fields inherited from interface io.github.pr0methean.betterrandom.seed.SeedGenerator

EMPTY_SEED

Constructor Summary

Constructors

Constructor	Description
SecureRandomSeedGenerator(SecureRandom source)	Creates an instance.

Method Summary

Modifier and Type	Method	Description
boolean	equals(Object o)
void	generateSeed(byte[] output)	Generates a seed value for a random number generator in an existing array.
byte[]	generateSeed(int length)	Generates and returns a seed value for a random number generator as a new array.
int	hashCode()
boolean	isWorthTrying()	Returns true if we cannot determine quickly (i.e.
protected Object	readResolve()
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_INSTANCE

public static final SecureRandomSeedGenerator DEFAULT_INSTANCE

The default instance. (This class was formerly a singleton.)

Constructor Detail

SecureRandomSeedGenerator

public SecureRandomSeedGenerator(SecureRandom source)

Creates an instance.

Parameters:

source - the SecureRandom whose SecureRandom.generateSeed(int) method will provide seeds

Method Detail

readResolve

protected Object readResolve()

generateSeed

public byte[] generateSeed(int length)

Generates and returns a seed value for a random number generator as a new array.

Specified by:

generateSeed in interface SeedGenerator

Parameters:

length - The length of the seed to generate (in bytes).

Returns:

A byte array containing the seed data.

Throws:

SeedException - If a seed cannot be generated for any reason.

generateSeed

public void generateSeed(byte[] output)

Description copied from interface: SeedGenerator

Generates a seed value for a random number generator in an existing array.

Specified by:

generateSeed in interface SeedGenerator

Parameters:

output - The array that is to be populated with the seed.

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

isWorthTrying

public boolean isWorthTrying()

Returns true if we cannot determine quickly (i.e. without I/O calls) that this SeedGenerator would throw a SeedException if generateSeed(int) or generateSeed(byte[]) were being called right now.

Specified by:

isWorthTrying in interface SeedGenerator

Returns:

true if this SeedGenerator will get as far as an I/O call or other slow operation in attempting to generate a seed immediately.