org.bouncycastle.crypto.util.BasicEntropySourceProvider Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of bc-fips-debug Show documentation

The FIPS 140-2 Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms certified to FIPS 140-2 level 1. This jar contains the debug version JCE provider and low-level API for the BC-FJA version 1.0.2.3, FIPS Certificate #3514. Please note the debug jar is not certified.

There is a newer version: 2.0.0

Show newest version

package org.bouncycastle.crypto.util;

import java.security.SecureRandom;

import org.bouncycastle.crypto.EntropySource;
import org.bouncycastle.crypto.EntropySourceProvider;
import org.bouncycastle.crypto.OutputXOFCalculator;
import org.bouncycastle.crypto.UpdateOutputStream;
import org.bouncycastle.crypto.fips.FipsEntropyConfig;
import org.bouncycastle.crypto.fips.FipsSHS;
import org.bouncycastle.crypto.fips.FipsSecureRandom;
import org.bouncycastle.crypto.general.GeneralSecureRandom;

/**
 * An EntropySourceProvider where entropy generation is based on a SecureRandom output using SecureRandom.generateSeed() in
 * the case of a JDK SecureRandom or SecureRandom.nextBytes() in the case of a FipsSecureRandom, or a GeneralSecureRandom.
 */
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 our RNG suitable for use for seeding?
                if (_sr instanceof FipsSecureRandom || _sr instanceof GeneralSecureRandom)
                {
                    byte[] rv = new byte[(bitsRequired + 7) / 8];

                    _sr.nextBytes(rv);

                    return rv;
                }

                // fall back to the seed generator
                if (FipsEntropyConfig.getH() != 8.0f)
                {
                    // in this case we need to request more bits than required and use
                    // a recognised conditioning function to produce the right amount of data.
                    // We use the SHAKE256 hash function as it's XOF ability allows us to adjust
                    // the output size to match what's required.
                    int neededBits = (int)((bitsRequired / FipsEntropyConfig.getH()) + 1);

                    byte[] noise = _sr.generateSeed((neededBits + 7) / 8);

                    OutputXOFCalculator shake256 = new FipsSHS.XOFOperatorFactory().createOutputXOFCalculator(FipsSHS.SHAKE256);

                    UpdateOutputStream uOut = shake256.getFunctionStream();

                    uOut.update(noise);

                    uOut.finished();

                    return shake256.getFunctionOutput((bitsRequired + 7) / 8);
                }
                else
                {
                    return _sr.generateSeed((bitsRequired + 7) / 8);
                }
            }

            public int entropySize()
            {
                return bitsRequired;
            }
        };
    }
}