net.i2p.util
Class FortunaRandomSource

java.lang.Object
  extended by java.util.Random
      extended by java.security.SecureRandom
          extended by net.i2p.util.RandomSource
              extended by net.i2p.util.FortunaRandomSource
All Implemented Interfaces:
java.io.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
FortunaRandomSource(I2PAppContext context)
           
 
Method Summary
 void feedEntropy(java.lang.String source, byte[] data, int offset, int len)
          reseed the fortuna
 void feedEntropy(java.lang.String source, long data, int bitoffset, int bits)
          reseed the fortuna
 EntropyHarvester harvester()
           
static void main(java.lang.String[] args)
           
protected  int nextBits(int numBits)
          Pull the next numBits of random data off the fortuna instance (returning -2^numBits-1 through 2^numBits-1
 boolean nextBoolean()
          override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)
 void nextBytes(byte[] buf)
          override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)
 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()
          override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)
 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()
          override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)
 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)
           
 
Methods inherited from class net.i2p.util.RandomSource
getInstance, initSeed, loadSeed, saveSeed, writeSeed
 
Methods inherited from class java.security.SecureRandom
generateSeed, getAlgorithm, getInstance, getInstance, getInstance, getProvider, getSeed, next, setSeed
 
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)
Method Detail

setSeed

public void setSeed(byte[] buf)
Overrides:
setSeed in class java.security.SecureRandom

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. WTF. 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.

Overrides:
nextInt in class RandomSource

nextInt

public int nextInt()
Description copied from class: RandomSource
override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)

Overrides:
nextInt in class RandomSource

nextLong

public long nextLong(long n)
Like the modified nextInt, nextLong(n) returns a random number from 0 through n, including 0, excluding n.

Overrides:
nextLong in class RandomSource

nextLong

public long nextLong()
Description copied from class: RandomSource
override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)

Overrides:
nextLong in class RandomSource

nextBoolean

public boolean nextBoolean()
Description copied from class: RandomSource
override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)

Overrides:
nextBoolean in class RandomSource

nextBytes

public void nextBytes(byte[] buf)
Description copied from class: RandomSource
override as synchronized, for those JVMs that don't always pull via nextBytes (cough ibm)

Overrides:
nextBytes in class RandomSource

nextDouble

public double nextDouble()
Implementation from sun's java.util.Random javadocs

Overrides:
nextDouble in class RandomSource

nextFloat

public float nextFloat()
Implementation from sun's java.util.Random javadocs

Overrides:
nextFloat in class RandomSource

nextGaussian

public double nextGaussian()
Implementation from sun's java.util.Random javadocs

Overrides:
nextGaussian in class RandomSource

nextBits

protected int nextBits(int numBits)
Pull the next numBits of random data off the fortuna instance (returning -2^numBits-1 through 2^numBits-1


harvester

public EntropyHarvester harvester()
Overrides:
harvester in class RandomSource

feedEntropy

public void feedEntropy(java.lang.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

feedEntropy

public void feedEntropy(java.lang.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

main

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