71 lines
1.5 KiB
C#
71 lines
1.5 KiB
C#
using System;
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using Org.BouncyCastle.Asn1;
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using Org.BouncyCastle.Asn1.X509;
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using Org.BouncyCastle.Crypto.Generators;
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using Org.BouncyCastle.Crypto.Parameters;
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namespace Org.BouncyCastle.Crypto.Agreement.Kdf
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{
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/**
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* X9.63 based key derivation function for ECDH CMS.
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*/
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public class ECDHKekGenerator
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: IDerivationFunction
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{
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private readonly IDerivationFunction kdf;
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private DerObjectIdentifier algorithm;
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private int keySize;
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private byte[] z;
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public ECDHKekGenerator(
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IDigest digest)
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{
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this.kdf = new Kdf2BytesGenerator(digest);
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}
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public void Init(
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IDerivationParameters param)
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{
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DHKdfParameters parameters = (DHKdfParameters)param;
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this.algorithm = parameters.Algorithm;
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this.keySize = parameters.KeySize;
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this.z = parameters.GetZ(); // TODO Clone?
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}
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public IDigest Digest
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{
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get { return kdf.Digest; }
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}
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public int GenerateBytes(
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byte[] outBytes,
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int outOff,
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int len)
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{
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// ECC-CMS-SharedInfo
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DerSequence s = new DerSequence(
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new AlgorithmIdentifier(algorithm, DerNull.Instance),
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new DerTaggedObject(true, 2, new DerOctetString(integerToBytes(keySize))));
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kdf.Init(new KdfParameters(z, s.GetDerEncoded()));
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return kdf.GenerateBytes(outBytes, outOff, len);
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}
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private byte[] integerToBytes(int keySize)
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{
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byte[] val = new byte[4];
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val[0] = (byte)(keySize >> 24);
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val[1] = (byte)(keySize >> 16);
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val[2] = (byte)(keySize >> 8);
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val[3] = (byte)keySize;
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return val;
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}
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}
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}
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