freenet.crypt

Class Yarrow

java.lang.Object

java.util.Random

freenet.crypt.RandomSource

freenet.crypt.Yarrow

All Implemented Interfaces:

PersistentRandomSource, java.io.Serializable

public class Yarrow
extends RandomSource
implements PersistentRandomSource

An implementation of the Yarrow PRNG in Java.

This class implements Yarrow-160, a cryptraphically secure PRNG developed by John Kelsey, Bruce Schneier, and Neils Ferguson. It was designed to follow the specification (www.counterpane.com/labs) given in the paper by the same authors, with the following exceptions:

• Instead of 3DES as the output cipher, Rijndael was chosen. It was my belief that an AES candidate should be selected. Twofish was an alternate choice, but the AES implementation does not allow easy selection of a faster key-schedule, so twofish's severely impaired performance.
• h prime, described as a 'size adaptor' was not used, since its function is only to constrain the size of a byte array, our own key generation routine was used instead (See freenet.crypt.Util.makeKey)
• Our own entropy estimation routines are used, as they use a third-order delta calculation that is quite conservative. Still, its used along side the global multiplier and program- supplied guesses, as suggested.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
java.io.File	seedfile

Constructor Summary

Constructors

Constructor and Description
Yarrow()
Yarrow(boolean canBlock)
Yarrow(java.io.File seed)
Yarrow(java.io.File seed, java.lang.String digest, java.lang.String cipher, boolean updateSeed, boolean canBlock)
Yarrow(java.lang.String seed, java.lang.String digest, java.lang.String cipher, boolean updateSeed, boolean canBlock)

Method Summary

Modifier and Type	Method and Description
int	acceptEntropy(EntropySource source, long data, int entropyGuess) Accepts entropy data from a source
int	acceptEntropyBytes(EntropySource source, byte[] buf, int offset, int length, double bias) Accepts larger amounts of entropy data from a source, with a bias
int	acceptTimerEntropy(EntropySource timer) Accepts entropy in the form of timing data from a source
int	acceptTimerEntropy(EntropySource timer, double bias) Accept entropy from a source with a bias
void	close() If the RandomSource has any resources it wants to close, it can do so when this method is called
static void	main(java.lang.String[] args) Test routine
protected int	next(int bits)
protected void	readStartupEntropy(EntropySource startupEntropy)
void	waitForEntropy(int bits) If entropy estimation is supported, this method will block until the specified number of bits of entropy are available.
void	write_seed(boolean force) Explanation of the purpose of this mechanism is at its interface PersistentRandomSource.

Methods inherited from class freenet.crypt.RandomSource

nextFullDouble, nextFullFloat

Methods inherited from class java.util.Random

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, 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

Field Detail

seedfile

public final java.io.File seedfile

Constructor Detail

Yarrow

public Yarrow()

Yarrow

public Yarrow(boolean canBlock)

Yarrow

public Yarrow(java.io.File seed)

Yarrow

public Yarrow(java.lang.String seed,
              java.lang.String digest,
              java.lang.String cipher,
              boolean updateSeed,
              boolean canBlock)

Yarrow

public Yarrow(java.io.File seed,
              java.lang.String digest,
              java.lang.String cipher,
              boolean updateSeed,
              boolean canBlock)

Method Detail

readStartupEntropy

protected void readStartupEntropy(EntropySource startupEntropy)

write_seed

public void write_seed(boolean force)

Explanation of the purpose of this mechanism is at its interface PersistentRandomSource.

Specified by:

write_seed in interface PersistentRandomSource

Parameters:

force - If false, the implementation might decide to ignore this function call if the seed file was written to disk a short time ago already.

next

protected int next(int bits)

Overrides:

next in class RandomSource

acceptEntropy

public int acceptEntropy(EntropySource source,
                         long data,
                         int entropyGuess)

Description copied from class: RandomSource

Accepts entropy data from a source

Specified by:

acceptEntropy in class RandomSource

acceptEntropyBytes

public int acceptEntropyBytes(EntropySource source,
                              byte[] buf,
                              int offset,
                              int length,
                              double bias)

Description copied from class: RandomSource

Accepts larger amounts of entropy data from a source, with a bias

Specified by:

acceptEntropyBytes in class RandomSource

Parameters:

source - The source from which the data has come.

buf - The buffer to read bytes from.

offset - The offset to start reading from.

length - The number of bytes to read.

bias - The bias. Value by which we multiply the entropy before counting it. Must be <= 1.0.

acceptTimerEntropy

public int acceptTimerEntropy(EntropySource timer)

Description copied from class: RandomSource

Accepts entropy in the form of timing data from a source

Specified by:

acceptTimerEntropy in class RandomSource

acceptTimerEntropy

public int acceptTimerEntropy(EntropySource timer,
                              double bias)

Description copied from class: RandomSource

Accept entropy from a source with a bias

Specified by:

acceptTimerEntropy in class RandomSource

bias - Value by which we multiply the entropy before counting it. Must be <= 1.0.

waitForEntropy

public void waitForEntropy(int bits)

If entropy estimation is supported, this method will block until the specified number of bits of entropy are available. If estimation isn't supported, this method will return immediately.

Overrides:

waitForEntropy in class RandomSource

close

public void close()

If the RandomSource has any resources it wants to close, it can do so when this method is called

Specified by:

close in class RandomSource

main

public static void main(java.lang.String[] args)
                 throws java.lang.Exception

Test routine

Throws:

java.lang.Exception