BigSpeed File Sharing SDK includes two ActiveX controls (client and server) that dramatically simplify and accelerate the development of private file sharing solutions over the Internet. In addition to standard FTP operations, such as upload, download, rename, delete, etc., the library also offers a number of advanced features which give the local application full control over the remote files. The client is able to open seekable streams on the server, either in read-only or read-write access mode. The application can seek, read, an write bytes to the stream as it is a local file. The client is able to run search operation on the server. The searching criteria may include file name masks (wildcards), text strings inside the files, or both of them. The found items are reported in real-time, while the operation is running. The server is able to perform remote file compression and decompression by a request from the client. During zipping or unzipping detailed progress information is provided back to the client about the current and total file and byte counts. The transfered data are scrambled using on-the-fly 128-bit AES encryption, without need of SSL certificates. The security is provided in two different modes: symmetric encryption with shared secret key and asymmetric encryptionwith 1024-bit public/private keys. There is an option to compress on-the-fly the outgoing data before encrypting, which may reduce greatly the transfer time for large files. BigSpeed File Sharing SDK 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 are included in Visual Basic 6, Visual Basic .NET, Visual C++ .NET, and Delphi 7.