package org.bouncycastle.crypto.agreement.kdf;
import org.bouncycastle.asn1.ASN1EncodableVector;
import org.bouncycastle.asn1.DERNull;
import org.bouncycastle.asn1.DERObjectIdentifier;
import org.bouncycastle.asn1.DEROctetString;
import org.bouncycastle.asn1.DERSequence;
import org.bouncycastle.asn1.DERTaggedObject;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.DerivationFunction;
import org.bouncycastle.crypto.DerivationParameters;
import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.generators.KDF2BytesGenerator;
import org.bouncycastle.crypto.params.KDFParameters;
/**
* X9.63 based key derivation function for ECDH CMS.
*/
public class ECDHKEKGenerator
implements DerivationFunction
{
private DerivationFunction kdf;
private DERObjectIdentifier algorithm;
private int keySize;
private byte[] z;
public ECDHKEKGenerator(
Digest digest)
{
this.kdf = new KDF2BytesGenerator(digest);
}
public void init(DerivationParameters param)
{
DHKDFParameters params = (DHKDFParameters)param;
this.algorithm = params.getAlgorithm();
this.keySize = params.getKeySize();
this.z = params.getZ();
}
public Digest getDigest()
{
return kdf.getDigest();
}
public int generateBytes(byte[] out, int outOff, int len)
throws DataLengthException, IllegalArgumentException
{
// ECC-CMS-SharedInfo
ASN1EncodableVector v = new ASN1EncodableVector();
v.add(new AlgorithmIdentifier(algorithm, new DERNull()));
v.add(new DERTaggedObject(true, 2, new DEROctetString(integerToBytes(keySize))));
kdf.init(new KDFParameters(z, new DERSequence(v).getDEREncoded()));
return kdf.generateBytes(out, outOff, len);
}
private byte[] integerToBytes(int keySize)
{
byte[] val = new byte[4];
val[0] = (byte)(keySize >> 24);
val[1] = (byte)(keySize >> 16);
val[2] = (byte)(keySize >> 8);
val[3] = (byte)keySize;
return val;
}
}