Net.Pkcs11Interop.HighLevelAPI81.Session.DecryptVerify C# (CSharp) Method

        public void DecryptVerify(Mechanism verificationMechanism, ObjectHandle verificationKeyHandle, Mechanism decryptionMechanism, ObjectHandle decryptionKeyHandle, Stream inputStream, Stream outputStream, byte[] signature, out bool isValid, int bufferLength)
        {
            if (this._disposed)
                throw new ObjectDisposedException(this.GetType().FullName);

            if (verificationMechanism == null)
                throw new ArgumentNullException("verificationMechanism");
            
            if (verificationKeyHandle == null)
                throw new ArgumentNullException("verificationKeyHandle");
            
            if (decryptionMechanism == null)
                throw new ArgumentNullException("decryptionMechanism");
            
            if (decryptionKeyHandle == null)
                throw new ArgumentNullException("decryptionKeyHandle");
            
            if (inputStream == null)
                throw new ArgumentNullException("inputStream");
            
            if (outputStream == null)
                throw new ArgumentNullException("outputStream");
            
            if (signature == null)
                throw new ArgumentNullException("signature");

            if (bufferLength < 1)
                throw new ArgumentException("Value has to be positive number", "bufferLength");

            CK_MECHANISM ckVerificationMechanism = verificationMechanism.CkMechanism;

            CKR rv = _p11.C_VerifyInit(_sessionId, ref ckVerificationMechanism, verificationKeyHandle.ObjectId);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_VerifyInit", rv);

            CK_MECHANISM ckDecryptionMechanism = decryptionMechanism.CkMechanism;

            rv = _p11.C_DecryptInit(_sessionId, ref ckDecryptionMechanism, decryptionKeyHandle.ObjectId);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_DecryptInit", rv);

            byte[] encryptedPart = new byte[bufferLength];
            byte[] part = new byte[bufferLength];
            ulong partLen = Convert.ToUInt64(part.Length);

            int bytesRead = 0;
            while ((bytesRead = inputStream.Read(encryptedPart, 0, encryptedPart.Length)) > 0)
            {
                partLen = Convert.ToUInt64(part.Length);
                rv = _p11.C_DecryptVerifyUpdate(_sessionId, encryptedPart, Convert.ToUInt64(bytesRead), part, ref partLen);
                if (rv != CKR.CKR_OK)
                    throw new Pkcs11Exception("C_DecryptVerifyUpdate", rv);

                outputStream.Write(part, 0, Convert.ToInt32(partLen));
            }

            byte[] lastPart = null;
            ulong lastPartLen = 0;
            rv = _p11.C_DecryptFinal(_sessionId, null, ref lastPartLen);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_DecryptFinal", rv);

            lastPart = new byte[lastPartLen];
            rv = _p11.C_DecryptFinal(_sessionId, lastPart, ref lastPartLen);
            if (rv != CKR.CKR_OK)
                throw new Pkcs11Exception("C_DecryptFinal", rv);

            if (lastPartLen > 0)
                outputStream.Write(lastPart, 0, Convert.ToInt32(lastPartLen));

            rv = _p11.C_VerifyFinal(_sessionId, signature, Convert.ToUInt64(signature.Length));
            if (rv == CKR.CKR_OK)
                isValid = true;
            else if (rv == CKR.CKR_SIGNATURE_INVALID)
                isValid = false;
            else 
                throw new Pkcs11Exception("C_VerifyFinal", rv);
        }