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package org.bouncycastle.crypto.prng;
import java.security.SecureRandom;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.util.Pack;
public class X931SecureRandomBuilder
{
private SecureRandom random; // JDK 1.1 complains on final.
private EntropySourceProvider entropySourceProvider;
private BlockCipher engine;
private byte[] dateTimeVector;
/**
* Basic constructor, creates a builder using an EntropySourceProvider based on the default SecureRandom with
* predictionResistant set to false.
* <p>
* Any SecureRandom created from a builder constructed like this will make use of input passed to SecureRandom.setSeed() if
* the default SecureRandom does for its generateSeed() call.
* </p>
*/
public X931SecureRandomBuilder()
{
this(new SecureRandom(), false);
}
/**
* Construct a builder with an EntropySourceProvider based on the passed in SecureRandom and the passed in value
* for prediction resistance.
* <p>
* Any SecureRandom created from a builder constructed like this will make use of input passed to SecureRandom.setSeed() if
* the passed in SecureRandom does for its generateSeed() call.
* </p>
* @param entropySource
* @param predictionResistant
*/
public X931SecureRandomBuilder(SecureRandom entropySource, boolean predictionResistant)
{
this.random = entropySource;
this.entropySourceProvider = new BasicEntropySourceProvider(random, predictionResistant);
}
/**
* Create a builder which makes creates the SecureRandom objects from a specified entropy source provider.
* <p>
* <b>Note:</b> If this constructor is used any calls to setSeed() in the resulting SecureRandom will be ignored.
* </p>
* @param entropySourceProvider a provider of EntropySource objects.
*/
public X931SecureRandomBuilder(EntropySourceProvider entropySourceProvider)
{
this.random = null;
this.entropySourceProvider = entropySourceProvider;
}
public X931SecureRandomBuilder setDateTimeVector(byte[] dateTimeVector)
{
this.dateTimeVector = dateTimeVector;
return this;
}
/**
* Construct a X9.31 secure random generator using the passed in engine and key. If predictionResistant is true the
* generator will be reseeded on each request.
*
* @param engine a block cipher to use as the operator.
* @param key the block cipher key to initialise engine with.
* @param predictionResistant true if engine to be reseeded on each use, false otherwise.
* @return a SecureRandom.
*/
public X931SecureRandom build(BlockCipher engine, KeyParameter key, boolean predictionResistant)
{
this.engine = engine;
if (dateTimeVector == null)
{
if (engine.getBlockSize() == 8)
{
dateTimeVector = Pack.longToBigEndian(System.currentTimeMillis());
}
else
{
dateTimeVector = new byte[engine.getBlockSize()];
byte[] date = Pack.longToBigEndian(System.currentTimeMillis());
System.arraycopy(date, 0, dateTimeVector, 0, date.length);
}
}
engine.init(true, key);
return new X931SecureRandom(random, new X931RNG(engine, dateTimeVector, entropySourceProvider.get(engine.getBlockSize() * 8)), predictionResistant);
}
}
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