org.bouncycastle.crypto.prng.BasicEntropySourceProvider Maven / Gradle / Ivy
package org.bouncycastle.crypto.prng;
import java.security.SecureRandom;
/**
* An EntropySourceProvider where entropy generation is based on a SecureRandom output using SecureRandom.generateSeed().
*/
public class BasicEntropySourceProvider
implements EntropySourceProvider
{
private final SecureRandom _sr;
private final boolean _predictionResistant;
/**
* Create a entropy source provider based on the passed in SecureRandom.
*
* @param random the SecureRandom to base EntropySource construction on.
* @param isPredictionResistant boolean indicating if the SecureRandom is based on prediction resistant entropy or not (true if it is).
*/
public BasicEntropySourceProvider(SecureRandom random, boolean isPredictionResistant)
{
_sr = random;
_predictionResistant = isPredictionResistant;
}
/**
* Return an entropy source that will create bitsRequired bits of entropy on
* each invocation of getEntropy().
*
* @param bitsRequired size (in bits) of entropy to be created by the provided source.
* @return an EntropySource that generates bitsRequired bits of entropy on each call to its getEntropy() method.
*/
public EntropySource get(final int bitsRequired)
{
return new EntropySource()
{
public boolean isPredictionResistant()
{
return _predictionResistant;
}
public byte[] getEntropy()
{
// is the RNG regarded as useful for seeding?
if (_sr instanceof SP800SecureRandom || _sr instanceof X931SecureRandom)
{
byte[] rv = new byte[(bitsRequired + 7) / 8];
_sr.nextBytes(rv);
return rv;
}
return _sr.generateSeed((bitsRequired + 7) / 8);
}
public int entropySize()
{
return bitsRequired;
}
};
}
}