83 lines
1.7 KiB
C#
83 lines
1.7 KiB
C#
using System;
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using Org.BouncyCastle.Crypto;
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namespace Org.BouncyCastle.Crypto.Digests
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{
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/**
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* Wrapper class that reduces the output length of a particular digest to
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* only the first n bytes of the digest function.
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*/
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public class ShortenedDigest
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: IDigest
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{
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private IDigest baseDigest;
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private int length;
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/**
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* Base constructor.
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*
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* @param baseDigest underlying digest to use.
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* @param length length in bytes of the output of doFinal.
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* @exception ArgumentException if baseDigest is null, or length is greater than baseDigest.GetDigestSize().
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*/
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public ShortenedDigest(
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IDigest baseDigest,
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int length)
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{
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if (baseDigest == null)
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{
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throw new ArgumentNullException("baseDigest");
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}
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if (length > baseDigest.GetDigestSize())
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{
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throw new ArgumentException("baseDigest output not large enough to support length");
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}
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this.baseDigest = baseDigest;
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this.length = length;
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}
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public string AlgorithmName
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{
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get { return baseDigest.AlgorithmName + "(" + length * 8 + ")"; }
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}
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public int GetDigestSize()
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{
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return length;
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}
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public void Update(byte input)
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{
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baseDigest.Update(input);
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}
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public void BlockUpdate(byte[] input, int inOff, int length)
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{
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baseDigest.BlockUpdate(input, inOff, length);
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}
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public int DoFinal(byte[] output, int outOff)
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{
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byte[] tmp = new byte[baseDigest.GetDigestSize()];
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baseDigest.DoFinal(tmp, 0);
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Array.Copy(tmp, 0, output, outOff, length);
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return length;
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}
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public void Reset()
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{
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baseDigest.Reset();
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}
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public int GetByteLength()
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{
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return baseDigest.GetByteLength();
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}
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}
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}
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