BIGSPEED Secure Socket Library: http://www.bigspeed.net/download.php?url=bssocklib/bssocklib_free_setup.exe
BigSpeed Secure Socket Library is a COM component that dramatically simplifies and accelerates the development of proprietary communication solutions over the Internet. It implements a flexible message-oriented protocol on top of a single TCP connection. The transfered data are scrambled using on-the-fly 128-bit AES encryption with random session keys, without need of SSL certificates. The security is provided in two different modes: symmetric encryption with shared secret key and asymmetric encryption with 1024-bit public/private keys. Transport level authentication is available with optional digital fingerprints or secret keys. Building a virtual private application network is just a matter of setting the same crypto key on two or more sites.
BigSpeed Secure Socket Library can be used both on client and server side, with centralized management of all connections. Information is exchanged through typed data packets identified by a command code. The library takes care of all low-level tasks: packetizing/depacketizing, compression/decompression, encryption/decryption, sending, receiving, buffer congestion and flow control. There is support for automatic DNS name resolution and SOCKS proxy servers.
BigSpeed Secure Socket Library utilizes an elegant event-driven paradigm for easy integration into Windows applications. A special attention is paid to provide responsive user interface while maintaining maximum bandwidth efficiency. Carefully designed set of properties, methods, and events offers great flexibility to develop innovative communication software. Sample applications for chat, alert messaging, and file transfer are included in Visual Basic 6, Visual Basic .NET, Visual C++ .NET, and Delphi 7.