Patch by Jerry:

* wrote CCryptoStream and supporting unit tests
* changed CStreamFilter to accept CMockEventQueue
* changed CStreamFilter's dtor to virtual because it is inherited

src/lib/synergy/CCryptoStream.h

@@ -0,0 +1,54 @@
+/*
+ * synergy -- mouse and keyboard sharing utility
+ * Copyright (C) 2013 Bolton Software Ltd.
+ * 
+ * This package is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * found in the file COPYING that should have accompanied this file.
+ * 
+ * This package is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "BasicTypes.h"
+#include "CStreamFilter.h"
+#include "cryptopp562/gcm.h"
+#include "cryptopp562/aes.h"
+
+//! Bidirectional encrypted stream
+/*!
+Encrypts (on write) and decrypts (on read) to and from an underlying stream.
+*/
+class CCryptoStream : public CStreamFilter {
+public:
+	CCryptoStream(IEventQueue& eventQueue, synergy::IStream* stream);
+	virtual ~CCryptoStream();
+
+	//! @name manipulators
+	//@{
+
+	//! Read from stream
+	/*!
+	Read up to \p n bytes into \p buffer to the stream using encryption.
+	Returns the number of bytes read by the underlying stream.
+	*/
+	virtual UInt32		read(void* out, UInt32 n);
+
+	//! Write to stream
+	/*!
+	Write \c n bytes from \c buffer to the stream using encryption.
+	*/
+	virtual void		write(const void* in, UInt32 n);
+
+private:
+	// TODO: allow user to change between GCM/CTR/CFB
+	CryptoPP::GCM<CryptoPP::AES>::Encryption		m_encryption;
+	CryptoPP::GCM<CryptoPP::AES>::Decryption		m_decryption;
+};