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using System;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto.Utilities;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities.Date;
namespace Org.BouncyCastle.Crypto.Prng
{
public class X931SecureRandomBuilder
{
private readonly SecureRandom mRandom; // JDK 1.1 complains on final.
private IEntropySourceProvider mEntropySourceProvider;
private byte[] mDateTimeVector;
/**
* 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, bool predictionResistant)
{
this.mRandom = entropySource;
this.mEntropySourceProvider = new BasicEntropySourceProvider(mRandom, 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(IEntropySourceProvider entropySourceProvider)
{
this.mRandom = null;
this.mEntropySourceProvider = entropySourceProvider;
}
public X931SecureRandomBuilder SetDateTimeVector(byte[] dateTimeVector)
{
this.mDateTimeVector = 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(IBlockCipher engine, KeyParameter key, bool predictionResistant)
{
if (mDateTimeVector == null)
{
mDateTimeVector = new byte[engine.GetBlockSize()];
Pack.UInt64_To_BE((ulong)DateTimeUtilities.CurrentUnixMs(), mDateTimeVector, 0);
}
engine.Init(true, key);
return new X931SecureRandom(mRandom, new X931Rng(engine, mDateTimeVector, mEntropySourceProvider.Get(engine.GetBlockSize() * 8)), predictionResistant);
}
}
}
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