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oracle.security.crypto.core
Class SpinnerEntropySource

java.lang.Object
oracle.security.crypto.core.EntropySource
oracle.security.crypto.core.SpinnerEntropySource

All Implemented Interfaces:

java.lang.Runnable

public class SpinnerEntropySource

extends EntropySource

implements java.lang.Runnable

A source of seeding entropy based on the presumption of intrinsic randomness in JVM thread scheduling, comparable to the "generateSeed" method in java.security.SecureRandom.

IMPORTANT: This class uses an experimental algorithm, which does not meet strong cryptographic standards for scalable entropy sources, which can only be provided by dedicated hardware or external signal sources. However, as such it is probably comparable to other software-only entropy-gathering techniques commonly in use, e.g. AWT- or keyboard-based entropy extractors, so-called entropy generating daemons (EGDs) based on periodic hashing of running system states, etc., and should be considered susceptible to similar vulnerabilities and performance constraints.

Also note that, since this is an experimental algorithm, its real entropy-gathering effectiveness is not well understood. Therefore, estimates of the entropy gathered should be very conservative. For example, if a lower bound of 1 bit of "true" randomness per byte generated is assumed, and if 160 bits of entropy are needed for secure seeding, then 160 bytes should be generated as PRNG seed material.

See Also:

RandomBitsSource

Constructor Summary

SpinnerEntropySource()
Create a new SpinnerEntropySource that will use the default thread sleep time (100 ms).

SpinnerEntropySource(int sleepTime)
Create a new SpinnerEntropySource that will use the given thread sleep time.

Method Summary

void	clear() Overrides the corresponding abstract method in the EntropySource class, but has no effect since there is no sensitive state data contained here for the JVM's thread scheduler.
byte	generateByte() Generate a byte of seeding material, obtained by casting the lowest 8 bits of a raw counter value.
int	getSleepTime() Return the delay parameter for the timeslice counter.
void	run() run() method from the Runnable interface.
void	setSleepTime(int sleepTime) Set the delay parameter for the timeslice counter.
java.lang.String	toString() Returns a description of this SpinnerEntropySource.

Methods inherited from class oracle.security.crypto.core.EntropySource

generateBytes, getDefault, setDefault

Methods inherited from class java.lang.Object

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

Constructor Detail

SpinnerEntropySource

public SpinnerEntropySource()

Create a new SpinnerEntropySource that will use the default thread sleep time (100 ms).

SpinnerEntropySource

public SpinnerEntropySource(int sleepTime)

Create a new SpinnerEntropySource that will use the given thread sleep time.

Parameters:

sleepTime - The thread sleep time, in milliseconds, that the spinner algorithm will use. Must be greater than 0, and should be greater than 10 for statistical reliability.

Method Detail

setSleepTime

public void setSleepTime(int sleepTime)

Set the delay parameter for the timeslice counter. (Default is 100 milliseconds.)

Parameters:

sleepTime - The thread sleep time, in milliseconds, that the spinner algorithm will use. Must be greater than 0, and should be greater than 10 for statistical reliability.

getSleepTime

public int getSleepTime()

Return the delay parameter for the timeslice counter.

generateByte

public byte generateByte()

Generate a byte of seeding material, obtained by casting the lowest 8 bits of a raw counter value.

Specified by:

generateByte in class EntropySource

run

public void run()

run() method from the Runnable interface.

Specified by:

run in interface java.lang.Runnable

clear

public void clear()

Overrides the corresponding abstract method in the EntropySource class, but has no effect since there is no sensitive state data contained here for the JVM's thread scheduler.

Specified by:

clear in class EntropySource

toString

public java.lang.String toString()

Returns a description of this SpinnerEntropySource.

Overrides:

toString in class java.lang.Object

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