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);
        }
        public virtual int GenerateBytes(byte[]	outBytes, int outOff, int len)
        {
            if ((outBytes.Length - len) < outOff)
            {
                throw new DataLengthException("output buffer too small");
            }

            long oBytes = len;
            int outLen = digest.GetDigestSize();

            //
            // this is at odds with the standard implementation, the
            // maximum value should be hBits * (2^32 - 1) where hBits
            // is the digest output size in bits. We can't have an
            // array with a long index at the moment...
            //
            if (oBytes > ((2L << 32) - 1))
            {
                throw new ArgumentException("Output length too large");
            }

            int cThreshold = (int)((oBytes + outLen - 1) / outLen);

            byte[] dig = new byte[digest.GetDigestSize()];

            uint counter = 1;

            for (int i = 0; i < cThreshold; i++)
            {
                digest.BlockUpdate(z, 0, z.Length);

                // KeySpecificInfo
                DerSequence keyInfo = new DerSequence(
                    algorithm,
                    new DerOctetString(Pack.UInt32_To_BE(counter)));

                // OtherInfo
                Asn1EncodableVector v1 = new Asn1EncodableVector(keyInfo);

                if (partyAInfo != null)
                {
                    v1.Add(new DerTaggedObject(true, 0, new DerOctetString(partyAInfo)));
                }

                v1.Add(new DerTaggedObject(true, 2, new DerOctetString(Pack.UInt32_To_BE((uint)keySize))));

                byte[] other = new DerSequence(v1).GetDerEncoded();

                digest.BlockUpdate(other, 0, other.Length);

                digest.DoFinal(dig, 0);

                if (len > outLen)
                {
                    Array.Copy(dig, 0, outBytes, outOff, outLen);
                    outOff += outLen;
                    len -= outLen;
                }
                else
                {
                    Array.Copy(dig, 0, outBytes, outOff, len);
                }

                counter++;
            }

            digest.Reset();

            return (int)oBytes;
        }
        public override Asn1Object ToAsn1Object()
        {
            DerSequence hashSeq = new DerSequence(datagroupHash);

            Asn1EncodableVector v = new Asn1EncodableVector(version, digestAlgorithmIdentifier, hashSeq);

            if (versionInfo != null)
            {
                v.Add(versionInfo);
            }

            return new DerSequence(v);
        }