This class generates seeds for the SHA1PRNG cryptographically strong random number generator.

The seed is produced using one of two techniques, via a computation of current system activity or from an entropy gathering device.

In the default technique the seed is produced by counting the number of times the VM manages to loop in a given period. This number roughly reflects the machine load at that point in time. The samples are translated using a permutation (s-box) and then XORed together. This process is non-linear and should prevent the samples from "averaging out". The s-box was designed to have even statistical distribution; its specific values are not crucial for the security of the seed. We also create a number of sleeper threads which add entropy to the system by keeping the scheduler busy. Twenty such samples should give us roughly 160 bits of randomness.

These values are gathered in the background by a daemon thread thus allowing the system to continue performing its different activities, which in turn add entropy to the random seed.

The class also gathers miscellaneous system information, some machine dependent, some not. This information is then hashed together with the 20 seed bytes.

The alternative to the above approach is to acquire seed material from an entropy gathering device, such as /dev/random. This can be accomplished by setting the value of the securerandom.source Security property to a URL specifying the location of the entropy gathering device, or by setting the java.security.egd System property.

In the event the specified URL cannot be accessed the default threading mechanism is used.

Nested and Inner Type Summary

Modifier and Type	Class and Description
private static class	SeedGenerator.ThreadedSeedGenerator
pack-priv static class	SeedGenerator.URLSeedGenerator

Field Summary

Modifier and Type	Field and Description
private static final Debug	debug
private static SeedGenerator	instance

Access	Constructor and Description
pack-priv	SeedGenerator()

Method Summary

Modifier and Type	Method and Description
private static void	addNetworkAdapterInfo(MessageDigest md)
public static void	generateSeed(byte[] result) Fill result with bytes from the queue.
pack-priv abstract void	getSeedBytes(byte[] result)
pack-priv static byte[]	getSystemEntropy() Retrieve some system information, hashed.
private static byte[]	longToByteArray(long l) Helper function to convert a long into a byte array (least significant byte first).

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Field Detail

debug	back to summary
private static final Debug debug

instance	back to summary
private static SeedGenerator instance

SeedGenerator	back to summary
pack-priv SeedGenerator()

Method Detail

addNetworkAdapterInfo	back to summary
private static void addNetworkAdapterInfo(MessageDigest md)

generateSeed	back to summary
public static void generateSeed(byte[] result) Fill result with bytes from the queue. Wait for it if it isn't ready.

getSeedBytes	back to summary
pack-priv abstract void getSeedBytes(byte[] result)

getSystemEntropy	back to summary
pack-priv static byte[] getSystemEntropy() Retrieve some system information, hashed.

longToByteArray	back to summary
private static byte[] longToByteArray(long l) Helper function to convert a long into a byte array (least significant byte first).

sun.security.provider back to summary

private Class SeedGenerator.ThreadedSeedGenerator

Class Inheritance

extends SeedGenerator
implements Runnable

java.lang.Object
sun.security.provider.SeedGenerator
sun.security.provider.SeedGenerator.ThreadedSeedGenerator

All Implemented Interfaces

java.lang.Runnable

Nested and Inner Type Summary

Modifier and Type	Class and Description
private static class	SeedGenerator.ThreadedSeedGenerator.BogusThread This inner thread causes the thread scheduler to become 'noisy', thus adding entropy to the system load.

Field Summary

Modifier and Type	Field and Description
private int	count
private int	end
private final byte[]	pool
private static final byte[]	rndTab
pack-priv ThreadGroup	seedGroup
private int	start

Constructor Summary

Access	Constructor and Description
pack-priv	ThreadedSeedGenerator() The constructor is only called once to construct the one instance we actually use.

Method Summary

Modifier and Type	Method and Description
pack-priv byte	getSeedByte()
pack-priv void	getSeedBytes(byte[] result) Implements abstract sun.security.provider.SeedGenerator.getSeedBytes.
public final void	run() Implements java.lang.Runnable.run. This method does the actual work.

Inherited from sun.security.provider.SeedGenerator:: generateSeed getSystemEntropy

Field Detail

count	back to summary
private int count

end	back to summary
private int end

pool	back to summary
private final byte[] pool

rndTab	back to summary
private static final byte[] rndTab

seedGroup	back to summary
pack-priv ThreadGroup seedGroup

start	back to summary
private int start

Constructor Detail

ThreadedSeedGenerator	back to summary
pack-priv ThreadedSeedGenerator() The constructor is only called once to construct the one instance we actually use. It instantiates the message digest and starts the thread going.

Method Detail

getSeedByte	back to summary
pack-priv byte getSeedByte()

getSeedBytes	back to summary
pack-priv void getSeedBytes(byte[] result) Implements abstract sun.security.provider.SeedGenerator.getSeedBytes. Annotations @Override

getSeedBytes

back to summary

pack-priv void getSeedBytes(byte[] result)

Implements abstract sun.security.provider.SeedGenerator.getSeedBytes.

Annotations

@Override

run	back to summary
public final void run() Implements java.lang.Runnable.run. This method does the actual work. It collects random bytes and pushes them into the queue. Annotations @Override

run

back to summary

public final void run()

Implements java.lang.Runnable.run.

This method does the actual work. It collects random bytes and pushes them into the queue.

Annotations

@Override

sun.security.provider back to summary

private Class SeedGenerator.ThreadedSeedGenerator.BogusThread

Class Inheritance

extends Object
implements Runnable

java.lang.Object
sun.security.provider.SeedGenerator.ThreadedSeedGenerator.BogusThread

All Implemented Interfaces

java.lang.Runnable

This inner thread causes the thread scheduler to become 'noisy', thus adding entropy to the system load. At least one instance of this class is generated for every seed byte.

Constructor Summary

Access	Constructor and Description
private	BogusThread()

Method Summary

Modifier and Type	Method and Description
public final void	run() Implements java.lang.Runnable.run. Runs this operation.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

Constructor Detail

BogusThread	back to summary
private BogusThread()

Method Detail

run	back to summary
public final void run() Implements java.lang.Runnable.run. Doc from java.lang.Runnable.run. Runs this operation. Annotations @Override

run

back to summary

public final void run()

Implements java.lang.Runnable.run.

Doc from java.lang.Runnable.run.

Runs this operation.

Annotations

@Override

sun.security.provider back to summary

pack-priv Class SeedGenerator.URLSeedGenerator

Class Inheritance

extends SeedGenerator

java.lang.Object
sun.security.provider.SeedGenerator
sun.security.provider.SeedGenerator.URLSeedGenerator

Known Direct Subclasses

sun.security.provider.NativeSeedGenerator

Field Summary

Modifier and Type	Field and Description
private final String	deviceName
private InputStream	seedStream

Constructor Summary

Access	Constructor and Description
pack-priv	URLSeedGenerator(String egdurl) The constructor is only called once to construct the one instance we actually use.

Method Summary

Modifier and Type	Method and Description
pack-priv void	getSeedBytes(byte[] result) Implements abstract sun.security.provider.SeedGenerator.getSeedBytes.
private void	init()

Inherited from sun.security.provider.SeedGenerator:: generateSeed getSystemEntropy

Field Detail

deviceName	back to summary
private final String deviceName

seedStream	back to summary
private InputStream seedStream

Constructor Detail

URLSeedGenerator	back to summary
pack-priv URLSeedGenerator(String egdurl) throws IOException The constructor is only called once to construct the one instance we actually use. It opens the entropy gathering device which will supply the randomness.

Method Detail

getSeedBytes	back to summary
pack-priv void getSeedBytes(byte[] result) Implements abstract sun.security.provider.SeedGenerator.getSeedBytes. Annotations @Override

getSeedBytes

back to summary

pack-priv void getSeedBytes(byte[] result)

Implements abstract sun.security.provider.SeedGenerator.getSeedBytes.

Annotations

@Override

init	back to summary
private void init() throws IOException

pack-priv abstract Class SeedGenerator

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private Class SeedGenerator.ThreadedSeedGenerator

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

private Class SeedGenerator.ThreadedSeedGenerator.BogusThread

Constructor Summary

Method Summary

Constructor Detail

Method Detail

pack-priv Class SeedGenerator.URLSeedGenerator

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail