net.i2p.util

Class FortunaRandomSource

java.lang.Object

java.util.Random

java.security.SecureRandom

net.i2p.util.RandomSource

net.i2p.util.FortunaRandomSource

All Implemented Interfaces:

Serializable, EntropyHarvester

public class FortunaRandomSource
extends RandomSource
implements EntropyHarvester

Wrapper around GNU-Crypto's Fortuna PRNG. This seeds from /dev/urandom and ./prngseed.rnd on startup (if they exist), writing a new seed to ./prngseed.rnd on an explicit call to saveSeed().

See Also:

Serialized Form

Field Summary

Fields inherited from class net.i2p.util.RandomSource

_context

Constructor Summary

Constructors

Constructor and Description
FortunaRandomSource(I2PAppContext context) May block up to 10 seconds or forever

Method Summary

Modifier and Type	Method and Description
void	feedEntropy(String source, byte[] data, int offset, int len) reseed the fortuna
void	feedEntropy(String source, long data, int bitoffset, int bits) reseed the fortuna
static void	main(String[] args) Outputs to stdout for dieharder: java -cp build/i2p.jar net.i2p.util.FortunaRandomSource | dieharder -a -g 200
protected int	nextBits(int numBits) Pull the next numBits of random data off the fortuna instance (returning 0 through 2^numBits-1 Caller must synchronize!
boolean	nextBoolean()
byte	nextByte() Not part of java.util.SecureRandom, but added for efficiency, since Fortuna supports it.
void	nextBytes(byte[] buf)
void	nextBytes(byte[] buf, int offset, int length) Not part of java.util.SecureRandom, but added for efficiency, since Fortuna supports it.
double	nextDouble() Implementation from sun's java.util.Random javadocs
float	nextFloat() Implementation from sun's java.util.Random javadocs
double	nextGaussian() Implementation from sun's java.util.Random javadocs
int	nextInt()
int	nextInt(int n) According to the java docs (http://java.sun.com/j2se/1.4.1/docs/api/java/util/Random.html#nextInt(int)) nextInt(n) should return a number between 0 and n (including 0 and excluding n).
long	nextLong()
long	nextLong(long n) Like the modified nextInt, nextLong(n) returns a random number from 0 through n, including 0, excluding n.
void	setSeed(byte[] buf)
void	shutdown() Note - methods may hang or NPE or throw IllegalStateExceptions after this
int	signedNextInt() This code unused, see FortunaRandomSource override

Methods inherited from class net.i2p.util.RandomSource

getInstance, harvester, initSeed, loadSeed, saveSeed, writeSeed

Methods inherited from class java.security.SecureRandom

generateSeed, getAlgorithm, getInstance, getInstance, getInstance, getInstanceStrong, getProvider, getSeed, next, setSeed

Methods inherited from class java.util.Random

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

Methods inherited from class java.lang.Object

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

Constructor Detail

FortunaRandomSource

public FortunaRandomSource(I2PAppContext context)

May block up to 10 seconds or forever

Method Detail

feedEntropy

public void feedEntropy(String source,
                        byte[] data,
                        int offset,
                        int len)

reseed the fortuna

Specified by:

feedEntropy in interface EntropyHarvester

Overrides:

feedEntropy in class RandomSource

Parameters:

source - origin of the entropy, allowing the harvester to determine how much to value the data

offset - index into the data array to start

len - how many bytes to use

feedEntropy

public void feedEntropy(String source,
                        long data,
                        int bitoffset,
                        int bits)

reseed the fortuna

Specified by:

feedEntropy in interface EntropyHarvester

Overrides:

feedEntropy in class RandomSource

Parameters:

source - origin of the entropy, allowing the harvester to determine how much to value the data

bitoffset - bit index into the data array to start (using java standard big-endian)

bits - how many bits to use

main

public static void main(String[] args)

Outputs to stdout for dieharder: java -cp build/i2p.jar net.i2p.util.FortunaRandomSource | dieharder -a -g 200

nextBits

protected int nextBits(int numBits)

Pull the next numBits of random data off the fortuna instance (returning 0 through 2^numBits-1 Caller must synchronize!

nextBoolean

public boolean nextBoolean()

Overrides:

nextBoolean in class Random

nextByte

public byte nextByte()

Not part of java.util.SecureRandom, but added for efficiency, since Fortuna supports it.

nextBytes

public void nextBytes(byte[] buf)

Overrides:

nextBytes in class SecureRandom

nextBytes

public void nextBytes(byte[] buf,
                      int offset,
                      int length)

Not part of java.util.SecureRandom, but added for efficiency, since Fortuna supports it.

Overrides:

nextBytes in class RandomSource

nextDouble

public double nextDouble()

Implementation from sun's java.util.Random javadocs

Overrides:

nextDouble in class Random

nextFloat

public float nextFloat()

Implementation from sun's java.util.Random javadocs

Overrides:

nextFloat in class Random

nextGaussian

public double nextGaussian()

Implementation from sun's java.util.Random javadocs

Overrides:

nextGaussian in class Random

nextInt

public int nextInt()

Overrides:

nextInt in class Random

nextInt

public int nextInt(int n)

According to the java docs (http://java.sun.com/j2se/1.4.1/docs/api/java/util/Random.html#nextInt(int)) nextInt(n) should return a number between 0 and n (including 0 and excluding n). However, their pseudocode, as well as sun's, kaffe's, and classpath's implementation INCLUDES NEGATIVE VALUES. Ok, so we're going to have it return between 0 and n (including 0, excluding n), since thats what it has been used for. Unlike Java's Random, which throws IAE, this returns 0 if n is 0.

Overrides:

nextInt in class RandomSource

Parameters:

n - non-negative

Throws:

IllegalArgumentException - if n is negative

nextLong

public long nextLong()

Overrides:

nextLong in class Random

Returns:

all possible long values, positive and negative

nextLong

public long nextLong(long n)

Like the modified nextInt, nextLong(n) returns a random number from 0 through n, including 0, excluding n. Unlike Java's Random, which throws IAE, this returns 0 if n is 0.

Overrides:

nextLong in class RandomSource

Parameters:

n - non-negative

Throws:

IllegalArgumentException - if n is negative

setSeed

public void setSeed(byte[] buf)

Overrides:

setSeed in class SecureRandom

shutdown

public void shutdown()

Note - methods may hang or NPE or throw IllegalStateExceptions after this

signedNextInt

public int signedNextInt()

Description copied from class: RandomSource

This code unused, see FortunaRandomSource override

Overrides:

signedNextInt in class RandomSource

Returns:

all possible int values, positive and negative