public byte[] unwrap(byte[] in, int inOff, int inLen)
            throws InvalidCipherTextException
    {

        if (forWrapping)
        {
            throw new IllegalStateException("Not set for unwrapping");
        }

        if (in == null)
        {
            throw new InvalidCipherTextException("Null pointer as ciphertext");
        }

        if (inLen % engine.getBlockSize() != 0)
        {
            throw new InvalidCipherTextException("Ciphertext not multiple of "
                    + engine.getBlockSize());
        }

        /*
         * // Check if the length of the cipher text is reasonable given the key //
         * type. It must be 40 bytes for a 168 bit key and either 32, 40, or //
         * 48 bytes for a 128, 192, or 256 bit key. If the length is not
         * supported // or inconsistent with the algorithm for which the key is
         * intended, // return error. // // we do not accept 168 bit keys. it
         * has to be 192 bit. int lengthA = (estimatedKeyLengthInBit / 8) + 16;
         * int lengthB = estimatedKeyLengthInBit % 8;
         * 
         * if ((lengthA != keyToBeUnwrapped.length) || (lengthB != 0)) { throw
         * new XMLSecurityException("empty"); }
         */

        // Decrypt the cipher text with TRIPLedeS in CBC mode using the KEK
        // and an initialization vector (IV) of 0x4adda22c79e82105. Call the
        // output TEMP3.
        ParametersWithIV param2 = new ParametersWithIV(this.param, IV2);

        this.engine.init(false, param2);

        byte TEMP3[] = new byte[inLen];

        System.arraycopy(in, inOff, TEMP3, 0, inLen);

        for (int i = 0; i < (TEMP3.length / engine.getBlockSize()); i++)
        {
            int currentBytePos = i * engine.getBlockSize();

            engine.processBlock(TEMP3, currentBytePos, TEMP3, currentBytePos);
        }

        // Reverse the order of the octets in TEMP3 and call the result TEMP2.
        byte[] TEMP2 = new byte[TEMP3.length];

        for (int i = 0; i < TEMP3.length; i++)
        {
            TEMP2[i] = TEMP3[TEMP3.length - (i + 1)];
        }

        // Decompose TEMP2 into IV, the first 8 octets, and TEMP1, the remaining
        // octets.
        this.iv = new byte[8];

        byte[] TEMP1 = new byte[TEMP2.length - 8];

        System.arraycopy(TEMP2, 0, this.iv, 0, 8);
        System.arraycopy(TEMP2, 8, TEMP1, 0, TEMP2.length - 8);

        // Decrypt TEMP1 using TRIPLedeS in CBC mode using the KEK and the IV
        // found in the previous step. Call the result WKCKS.
        this.paramPlusIV = new ParametersWithIV(this.param, this.iv);

        this.engine.init(false, this.paramPlusIV);

        byte[] LCEKPADICV = new byte[TEMP1.length];

        System.arraycopy(TEMP1, 0, LCEKPADICV, 0, TEMP1.length);

        for (int i = 0; i < (LCEKPADICV.length / engine.getBlockSize()); i++)
        {
            int currentBytePos = i * engine.getBlockSize();

            engine.processBlock(LCEKPADICV, currentBytePos, LCEKPADICV,
                    currentBytePos);
        }

        // Decompose LCEKPADICV. CKS is the last 8 octets and WK, the wrapped
        // key, are
        // those octets before the CKS.
        byte[] result = new byte[LCEKPADICV.length - 8];
        byte[] CKStoBeVerified = new byte[8];

        System.arraycopy(LCEKPADICV, 0, result, 0, LCEKPADICV.length - 8);
        System.arraycopy(LCEKPADICV, LCEKPADICV.length - 8, CKStoBeVerified, 0,
                8);

        // Calculate a CMS Key Checksum, (section 5.6.1), over the WK and
        // compare
        // with the CKS extracted in the above step. If they are not equal,
        // return error.
        if (!checkCMSKeyChecksum(result, CKStoBeVerified))
        {
            throw new InvalidCipherTextException(
                    "Checksum inside ciphertext is corrupted");
        }

        if ((result.length - ((result[0] & 0xff) + 1)) > 7)
        {
            throw new InvalidCipherTextException("too many pad bytes ("
                    + (result.length - ((result[0] & 0xff) + 1)) + ")");
        }

        // CEK is the wrapped key, now extracted for use in data decryption.
        byte[] CEK = new byte[result[0]];
        System.arraycopy(result, 1, CEK, 0, CEK.length);
        return CEK;
    }