118 lines
2.8 KiB
C#
118 lines
2.8 KiB
C#
using System;
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//using Org.BouncyCastle.Math;
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//using Org.BouncyCastle.Security;
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using Org.BouncyCastle.Crypto;
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using Org.BouncyCastle.Crypto.Parameters;
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namespace Org.BouncyCastle.Crypto.Generators
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{
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/**
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* Generator for MGF1 as defined in Pkcs 1v2
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*/
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public class Mgf1BytesGenerator : IDerivationFunction
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{
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private IDigest digest;
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private byte[] seed;
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private int hLen;
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/**
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* @param digest the digest to be used as the source of Generated bytes
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*/
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public Mgf1BytesGenerator(
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IDigest digest)
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{
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this.digest = digest;
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this.hLen = digest.GetDigestSize();
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}
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public void Init(
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IDerivationParameters parameters)
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{
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if (!(typeof(MgfParameters).IsInstanceOfType(parameters)))
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{
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throw new ArgumentException("MGF parameters required for MGF1Generator");
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}
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MgfParameters p = (MgfParameters)parameters;
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seed = p.GetSeed();
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}
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/**
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* return the underlying digest.
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*/
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public IDigest Digest
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{
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get
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{
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return digest;
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}
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}
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/**
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* int to octet string.
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*/
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private void ItoOSP(
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int i,
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byte[] sp)
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{
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sp[0] = (byte)((uint) i >> 24);
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sp[1] = (byte)((uint) i >> 16);
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sp[2] = (byte)((uint) i >> 8);
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sp[3] = (byte)((uint) i >> 0);
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}
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/**
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* fill len bytes of the output buffer with bytes Generated from
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* the derivation function.
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*
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* @throws DataLengthException if the out buffer is too small.
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*/
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public int GenerateBytes(
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byte[] output,
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int outOff,
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int length)
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{
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if ((output.Length - length) < outOff)
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{
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throw new DataLengthException("output buffer too small");
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}
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byte[] hashBuf = new byte[hLen];
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byte[] C = new byte[4];
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int counter = 0;
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digest.Reset();
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if (length > hLen)
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{
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do
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{
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ItoOSP(counter, C);
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digest.BlockUpdate(seed, 0, seed.Length);
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digest.BlockUpdate(C, 0, C.Length);
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digest.DoFinal(hashBuf, 0);
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Array.Copy(hashBuf, 0, output, outOff + counter * hLen, hLen);
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}
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while (++counter < (length / hLen));
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}
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if ((counter * hLen) < length)
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{
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ItoOSP(counter, C);
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digest.BlockUpdate(seed, 0, seed.Length);
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digest.BlockUpdate(C, 0, C.Length);
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digest.DoFinal(hashBuf, 0);
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Array.Copy(hashBuf, 0, output, outOff + counter * hLen, length - (counter * hLen));
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}
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return length;
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}
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}
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}
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