public SecretSubkeyPacket(
            PublicKeyPacket				pubKeyPacket,
            SymmetricKeyAlgorithmTag	encAlgorithm,
            S2k							s2k,
            byte[]						iv,
            byte[]						secKeyData)
            : base(pubKeyPacket, encAlgorithm, s2k, iv, secKeyData)
        {
        }
		public SymmetricKeyEncSessionPacket(
            SymmetricKeyAlgorithmTag	encAlgorithm,
            S2k							s2k,
            byte[]						secKeyData)
        {
            this.version = 4;
            this.encAlgorithm = encAlgorithm;
            this.s2k = s2k;
            this.secKeyData = secKeyData;
        }
        public SymmetricKeyEncSessionPacket(
            BcpgInputStream bcpgIn)
        {
            version = bcpgIn.ReadByte();
            encAlgorithm = (SymmetricKeyAlgorithmTag) bcpgIn.ReadByte();

            s2k = new S2k(bcpgIn);

            secKeyData = bcpgIn.ReadAll();
        }
		internal SecretKeyPacket(
            BcpgInputStream bcpgIn)
        {
			if (this is SecretSubkeyPacket)
			{
				pubKeyPacket = new PublicSubkeyPacket(bcpgIn);
			}
			else
			{
				pubKeyPacket = new PublicKeyPacket(bcpgIn);
			}

			s2kUsage = bcpgIn.ReadByte();

			if (s2kUsage == UsageChecksum || s2kUsage == UsageSha1)
            {
                encAlgorithm = (SymmetricKeyAlgorithmTag) bcpgIn.ReadByte();
                s2k = new S2k(bcpgIn);
            }
            else
            {
                encAlgorithm = (SymmetricKeyAlgorithmTag) s2kUsage;
			}

			if (!(s2k != null && s2k.Type == S2k.GnuDummyS2K && s2k.ProtectionMode == 0x01))
            {
				if (s2kUsage != 0)
				{
                    if (((int) encAlgorithm) < 7)
                    {
                        iv = new byte[8];
                    }
                    else
                    {
                        iv = new byte[16];
                    }
                    bcpgIn.ReadFully(iv);
                }
            }

			secKeyData = bcpgIn.ReadAll();
        }
		public SecretKeyPacket(
            PublicKeyPacket				pubKeyPacket,
            SymmetricKeyAlgorithmTag	encAlgorithm,
            S2k							s2k,
            byte[]						iv,
            byte[]						secKeyData)
        {
            this.pubKeyPacket = pubKeyPacket;
            this.encAlgorithm = encAlgorithm;

			if (encAlgorithm != SymmetricKeyAlgorithmTag.Null)
			{
				this.s2kUsage = UsageChecksum;
			}
			else
			{
				this.s2kUsage = UsageNone;
			}

			this.s2k = s2k;
			this.iv = Arrays.Clone(iv);
			this.secKeyData = secKeyData;
        }
		public SecretKeyPacket(
			PublicKeyPacket				pubKeyPacket,
			SymmetricKeyAlgorithmTag	encAlgorithm,
			int							s2kUsage,
			S2k							s2k,
			byte[]						iv,
			byte[]						secKeyData)
		{
			this.pubKeyPacket = pubKeyPacket;
			this.encAlgorithm = encAlgorithm;
			this.s2kUsage = s2kUsage;
			this.s2k = s2k;
			this.iv = Arrays.Clone(iv);
			this.secKeyData = secKeyData;
		}