/**
	     * generate an enveloped object that contains an CMS Enveloped Data
	     * object using the given provider and the passed in key generator.
	     */
		private CmsAuthenticatedData Generate(
			CmsProcessable		content,
			string				macOid,
			CipherKeyGenerator	keyGen)
		{
			AlgorithmIdentifier macAlgId;
			KeyParameter encKey;
			Asn1OctetString encContent;
			Asn1OctetString macResult;

			try
			{
				// FIXME Will this work for macs?
				byte[] encKeyBytes = keyGen.GenerateKey();
				encKey = ParameterUtilities.CreateKeyParameter(macOid, encKeyBytes);

				Asn1Encodable asn1Params = GenerateAsn1Parameters(macOid, encKeyBytes);

				ICipherParameters cipherParameters;
				macAlgId = GetAlgorithmIdentifier(
				macOid, encKey, asn1Params, out cipherParameters);

				IMac mac = MacUtilities.GetMac(macOid);
				// TODO Confirm no ParametersWithRandom needed
				// FIXME Only passing key at the moment
//	            mac.Init(cipherParameters);
				mac.Init(encKey);

				MemoryStream bOut = new MemoryStream();
				Stream mOut = new TeeOutputStream(bOut, new MacOutputStream(mac));

				content.Write(mOut);

				mOut.Dispose();
                bOut.Dispose();

				encContent = new BerOctetString(bOut.ToArray());

				byte[] macOctets = MacUtilities.DoFinal(mac);
				macResult = new DerOctetString(macOctets);
			}
			catch (SecurityUtilityException e)
			{
				throw new CmsException("couldn't create cipher.", e);
			}
			catch (InvalidKeyException e)
			{
				throw new CmsException("key invalid in message.", e);
			}
			catch (IOException e)
			{
				throw new CmsException("exception decoding algorithm parameters.", e);
			}

			Asn1EncodableVector recipientInfos = new Asn1EncodableVector();

			foreach (RecipientInfoGenerator rig in recipientInfoGenerators) 
			{
				try
				{
					recipientInfos.Add(rig.Generate(encKey, rand));
				}
				catch (InvalidKeyException e)
				{
					throw new CmsException("key inappropriate for algorithm.", e);
				}
				catch (GeneralSecurityException e)
				{
					throw new CmsException("error making encrypted content.", e);
				}
			}
			
			ContentInfo eci = new ContentInfo(CmsObjectIdentifiers.Data, encContent);
			
			ContentInfo contentInfo = new ContentInfo(
			CmsObjectIdentifiers.AuthenticatedData,
			new AuthenticatedData(null, new DerSet(recipientInfos), macAlgId, null, eci, null, macResult, null));
			
			return new CmsAuthenticatedData(contentInfo);
		}
		protected Stream Open(
			Stream        			outStr,
			AlgorithmIdentifier		macAlgId,
			ICipherParameters		cipherParameters,
			Asn1EncodableVector		recipientInfos)
		{
			try
			{
				//
				// ContentInfo
				//
				BerSequenceGenerator cGen = new BerSequenceGenerator(outStr);

				cGen.AddObject(CmsObjectIdentifiers.AuthenticatedData);

				//
				// Authenticated Data
				//
				BerSequenceGenerator authGen = new BerSequenceGenerator(
					cGen.GetRawOutputStream(), 0, true);

				authGen.AddObject(new DerInteger(AuthenticatedData.CalculateVersion(null)));

				Stream authRaw = authGen.GetRawOutputStream();
				Asn1Generator recipGen = _berEncodeRecipientSet
					?	(Asn1Generator) new BerSetGenerator(authRaw)
					:	new DerSetGenerator(authRaw);

				foreach (Asn1Encodable ae in recipientInfos)
				{
					recipGen.AddObject(ae);
				}

				recipGen.Close();

				authGen.AddObject(macAlgId);

				BerSequenceGenerator eiGen = new BerSequenceGenerator(authRaw);
				eiGen.AddObject(CmsObjectIdentifiers.Data);

				Stream octetOutputStream = CmsUtilities.CreateBerOctetOutputStream(
					eiGen.GetRawOutputStream(), 0, false, _bufferSize);

				IMac mac = MacUtilities.GetMac(macAlgId.ObjectID);
				// TODO Confirm no ParametersWithRandom needed
	            mac.Init(cipherParameters);
				Stream mOut = new TeeOutputStream(octetOutputStream, new MacOutputStream(mac));

				return new CmsAuthenticatedDataOutputStream(mOut, mac, cGen, authGen, eiGen);
			}
			catch (SecurityUtilityException e)
			{
				throw new CmsException("couldn't create cipher.", e);
			}
			catch (InvalidKeyException e)
			{
				throw new CmsException("key invalid in message.", e);
			}
			catch (IOException e)
			{
				throw new CmsException("exception decoding algorithm parameters.", e);
			}
		}