package org.bouncycastle.crypto.digests;

import org.bouncycastle.crypto.ExtendedDigest;

Wrapper class that reduces the output length of a particular digest to only the first n bytes of the digest function.
/** * Wrapper class that reduces the output length of a particular digest to * only the first n bytes of the digest function. */
public class ShortenedDigest implements ExtendedDigest { private ExtendedDigest baseDigest; private int length;
Base constructor.
Params:
  • baseDigest – underlying digest to use.
  • length – length in bytes of the output of doFinal.
Throws:
/** * Base constructor. * * @param baseDigest underlying digest to use. * @param length length in bytes of the output of doFinal. * @exception IllegalArgumentException if baseDigest is null, or length is greater than baseDigest.getDigestSize(). */
public ShortenedDigest( ExtendedDigest baseDigest, int length) { if (baseDigest == null) { throw new IllegalArgumentException("baseDigest must not be null"); } if (length > baseDigest.getDigestSize()) { throw new IllegalArgumentException("baseDigest output not large enough to support length"); } this.baseDigest = baseDigest; this.length = length; } public String getAlgorithmName() { return baseDigest.getAlgorithmName() + "(" + length * 8 + ")"; } public int getDigestSize() { return length; } public void update(byte in) { baseDigest.update(in); } public void update(byte[] in, int inOff, int len) { baseDigest.update(in, inOff, len); } public int doFinal(byte[] out, int outOff) { byte[] tmp = new byte[baseDigest.getDigestSize()]; baseDigest.doFinal(tmp, 0); System.arraycopy(tmp, 0, out, outOff, length); return length; } public void reset() { baseDigest.reset(); } public int getByteLength() { return baseDigest.getByteLength(); } }