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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8. Note: this package includes the NTRU encryption algorithms.

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package org.bouncycastle.crypto.generators;

import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.DerivationParameters;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.DigestDerivationFunction;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.params.ISO18033KDFParameters;
import org.bouncycastle.crypto.params.KDFParameters;
import org.bouncycastle.util.Pack;

/**
 * Basic KDF generator for derived keys and ivs as defined by IEEE P1363a/ISO
 * 18033 
* This implementation is based on ISO 18033/P1363a. */ public class BaseKDFBytesGenerator implements DigestDerivationFunction { private int counterStart; private Digest digest; private byte[] shared; private byte[] iv; /** * Construct a KDF Parameters generator. *

* * @param counterStart * value of counter. * @param digest * the digest to be used as the source of derived keys. */ protected BaseKDFBytesGenerator(int counterStart, Digest digest) { this.counterStart = counterStart; this.digest = digest; } public void init(DerivationParameters param) { if (param instanceof KDFParameters) { KDFParameters p = (KDFParameters)param; shared = p.getSharedSecret(); iv = p.getIV(); } else if (param instanceof ISO18033KDFParameters) { ISO18033KDFParameters p = (ISO18033KDFParameters)param; shared = p.getSeed(); iv = null; } else { throw new IllegalArgumentException("KDF parameters required for generator"); } } /** * return the underlying digest. */ public Digest getDigest() { return digest; } /** * fill len bytes of the output buffer with bytes generated from the * derivation function. * * @throws IllegalArgumentException * if the size of the request will cause an overflow. * @throws DataLengthException * if the out buffer is too small. */ public int generateBytes(byte[] out, int outOff, int len) throws DataLengthException, IllegalArgumentException { if ((out.length - len) < outOff) { throw new OutputLengthException("output buffer too small"); } long oBytes = len; int outLen = digest.getDigestSize(); // // this is at odds with the standard implementation, the // maximum value should be hBits * (2^32 - 1) where hBits // is the digest output size in bits. We can't have an // array with a long index at the moment... // if (oBytes > ((2L << 32) - 1)) { throw new IllegalArgumentException("Output length too large"); } int cThreshold = (int)((oBytes + outLen - 1) / outLen); byte[] dig = new byte[digest.getDigestSize()]; byte[] C = new byte[4]; Pack.intToBigEndian(counterStart, C, 0); int counterBase = counterStart & ~0xFF; for (int i = 0; i < cThreshold; i++) { digest.update(shared, 0, shared.length); digest.update(C, 0, C.length); if (iv != null) { digest.update(iv, 0, iv.length); } digest.doFinal(dig, 0); if (len > outLen) { System.arraycopy(dig, 0, out, outOff, outLen); outOff += outLen; len -= outLen; } else { System.arraycopy(dig, 0, out, outOff, len); } if (++C[3] == 0) { counterBase += 0x100; Pack.intToBigEndian(counterBase, C, 0); } } digest.reset(); return (int)oBytes; } }





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