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using System;
using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.X509;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto.Utilities;
namespace Org.BouncyCastle.Crypto.Agreement.Kdf
{
/**
* X9.63 based key derivation function for ECDH CMS.
*/
public class ECDHKekGenerator
: IDerivationFunction
{
private readonly IDerivationFunction kdf;
private DerObjectIdentifier algorithm;
private int keySize;
private byte[] z;
public ECDHKekGenerator(IDigest digest)
{
this.kdf = new Kdf2BytesGenerator(digest);
}
public virtual void Init(IDerivationParameters param)
{
DHKdfParameters parameters = (DHKdfParameters)param;
this.algorithm = parameters.Algorithm;
this.keySize = parameters.KeySize;
this.z = parameters.GetZ(); // TODO Clone?
}
public virtual IDigest Digest
{
get { return kdf.Digest; }
}
public virtual int GenerateBytes(byte[] outBytes, int outOff, int len)
{
// TODO Create an ASN.1 class for this (RFC3278)
// ECC-CMS-SharedInfo
DerSequence s = new DerSequence(
new AlgorithmIdentifier(algorithm, DerNull.Instance),
new DerTaggedObject(true, 2, new DerOctetString(Pack.UInt32_To_BE((uint)keySize))));
kdf.Init(new KdfParameters(z, s.GetDerEncoded()));
return kdf.GenerateBytes(outBytes, outOff, len);
}
}
}
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