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package org.bouncycastle.crypto.prng;
import java.security.SecureRandom;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CryptoServicesRegistrar;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.engines.DESedeEngine;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.prng.drbg.CTRSP800DRBG;
import org.bouncycastle.crypto.prng.drbg.HMacSP800DRBG;
import org.bouncycastle.crypto.prng.drbg.HashSP800DRBG;
import org.bouncycastle.crypto.prng.drbg.SP80090DRBG;
import org.bouncycastle.util.Arrays;
/**
* Builder class for making SecureRandom objects based on SP 800-90A Deterministic Random Bit Generators (DRBG).
*/
public class SP800SecureRandomBuilder
{
private final SecureRandom random;
private final EntropySourceProvider entropySourceProvider;
private byte[] personalizationString;
private int securityStrength = 256;
private int entropyBitsRequired = 256;
/**
* Basic constructor, creates a builder using an EntropySourceProvider based on the default SecureRandom with
* predictionResistant set to false.
*
* 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.
*
*/
public SP800SecureRandomBuilder()
{
this(CryptoServicesRegistrar.getSecureRandom(), false);
}
/**
* Construct a builder with an EntropySourceProvider based on the passed in SecureRandom and the passed in value
* for prediction resistance.
*
* 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.
*
* @param entropySource the SecureRandom acting as a source of entropy for DRBGs made by this builder.
* @param predictionResistant true if the SecureRandom seeder can be regarded as predictionResistant.
*/
public SP800SecureRandomBuilder(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.
*
* Note: If this constructor is used any calls to setSeed() in the resulting SecureRandom will be ignored.
*
* @param entropySourceProvider a provider of EntropySource objects.
*/
public SP800SecureRandomBuilder(EntropySourceProvider entropySourceProvider)
{
this.random = null;
this.entropySourceProvider = entropySourceProvider;
}
/**
* Set the personalization string for DRBG SecureRandoms created by this builder
* @param personalizationString the personalisation string for the underlying DRBG.
* @return the current builder.
*/
public SP800SecureRandomBuilder setPersonalizationString(byte[] personalizationString)
{
this.personalizationString = Arrays.clone(personalizationString);
return this;
}
/**
* Set the security strength required for DRBGs used in building SecureRandom objects.
*
* @param securityStrength the security strength (in bits)
* @return the current builder.
*/
public SP800SecureRandomBuilder setSecurityStrength(int securityStrength)
{
this.securityStrength = securityStrength;
return this;
}
/**
* Set the amount of entropy bits required for seeding and reseeding DRBGs used in building SecureRandom objects.
*
* @param entropyBitsRequired the number of bits of entropy to be requested from the entropy source on each seed/reseed.
* @return the current builder.
*/
public SP800SecureRandomBuilder setEntropyBitsRequired(int entropyBitsRequired)
{
this.entropyBitsRequired = entropyBitsRequired;
return this;
}
/**
* Build a SecureRandom based on a SP 800-90A Hash DRBG.
*
* @param digest digest algorithm to use in the DRBG underneath the SecureRandom.
* @param nonce nonce value to use in DRBG construction.
* @param predictionResistant specify whether the underlying DRBG in the resulting SecureRandom should reseed on each request for bytes.
* @return a SecureRandom supported by a Hash DRBG.
*/
public SP800SecureRandom buildHash(Digest digest, byte[] nonce, boolean predictionResistant)
{
return new SP800SecureRandom(random, entropySourceProvider.get(entropyBitsRequired), new HashDRBGProvider(digest, nonce, personalizationString, securityStrength), predictionResistant);
}
/**
* Build a SecureRandom based on a SP 800-90A CTR DRBG.
*
* @param cipher the block cipher to base the DRBG on.
* @param keySizeInBits key size in bits to be used with the block cipher.
* @param nonce nonce value to use in DRBG construction.
* @param predictionResistant specify whether the underlying DRBG in the resulting SecureRandom should reseed on each request for bytes.
* @return a SecureRandom supported by a CTR DRBG.
*/
public SP800SecureRandom buildCTR(BlockCipher cipher, int keySizeInBits, byte[] nonce, boolean predictionResistant)
{
return new SP800SecureRandom(random, entropySourceProvider.get(entropyBitsRequired), new CTRDRBGProvider(cipher, keySizeInBits, nonce, personalizationString, securityStrength), predictionResistant);
}
/**
* Build a SecureRandom based on a SP 800-90A HMAC DRBG.
*
* @param hMac HMAC algorithm to use in the DRBG underneath the SecureRandom.
* @param nonce nonce value to use in DRBG construction.
* @param predictionResistant specify whether the underlying DRBG in the resulting SecureRandom should reseed on each request for bytes.
* @return a SecureRandom supported by a HMAC DRBG.
*/
public SP800SecureRandom buildHMAC(Mac hMac, byte[] nonce, boolean predictionResistant)
{
return new SP800SecureRandom(random, entropySourceProvider.get(entropyBitsRequired), new HMacDRBGProvider(hMac, nonce, personalizationString, securityStrength), predictionResistant);
}
private static class HashDRBGProvider
implements DRBGProvider
{
private final Digest digest;
private final byte[] nonce;
private final byte[] personalizationString;
private final int securityStrength;
public HashDRBGProvider(Digest digest, byte[] nonce, byte[] personalizationString, int securityStrength)
{
this.digest = digest;
this.nonce = nonce;
this.personalizationString = personalizationString;
this.securityStrength = securityStrength;
}
public String getAlgorithm()
{
return "HASH-DRBG-" + getSimplifiedName(digest);
}
public SP80090DRBG get(EntropySource entropySource)
{
return new HashSP800DRBG(digest, securityStrength, entropySource, personalizationString, nonce);
}
}
private static class HMacDRBGProvider
implements DRBGProvider
{
private final Mac hMac;
private final byte[] nonce;
private final byte[] personalizationString;
private final int securityStrength;
public HMacDRBGProvider(Mac hMac, byte[] nonce, byte[] personalizationString, int securityStrength)
{
this.hMac = hMac;
this.nonce = nonce;
this.personalizationString = personalizationString;
this.securityStrength = securityStrength;
}
public String getAlgorithm()
{
if (hMac instanceof HMac)
{
return "HMAC-DRBG-" + getSimplifiedName(((HMac)hMac).getUnderlyingDigest());
}
return "HMAC-DRBG-" + hMac.getAlgorithmName();
}
public SP80090DRBG get(EntropySource entropySource)
{
return new HMacSP800DRBG(hMac, securityStrength, entropySource, personalizationString, nonce);
}
}
private static class CTRDRBGProvider
implements DRBGProvider
{
private final BlockCipher blockCipher;
private final int keySizeInBits;
private final byte[] nonce;
private final byte[] personalizationString;
private final int securityStrength;
public CTRDRBGProvider(BlockCipher blockCipher, int keySizeInBits, byte[] nonce, byte[] personalizationString, int securityStrength)
{
this.blockCipher = blockCipher;
this.keySizeInBits = keySizeInBits;
this.nonce = nonce;
this.personalizationString = personalizationString;
this.securityStrength = securityStrength;
}
public String getAlgorithm()
{
if (blockCipher instanceof DESedeEngine)
{
return "CTR-DRBG-3KEY-TDES";
}
return "CTR-DRBG-" + blockCipher.getAlgorithmName() + keySizeInBits;
}
public SP80090DRBG get(EntropySource entropySource)
{
return new CTRSP800DRBG(blockCipher, keySizeInBits, securityStrength, entropySource, personalizationString, nonce);
}
}
private static String getSimplifiedName(Digest digest)
{
String name = digest.getAlgorithmName();
int dIndex = name.indexOf('-');
if (dIndex > 0 && !name.startsWith("SHA3"))
{
return name.substring(0, dIndex) + name.substring(dIndex + 1);
}
return name;
}
}