2 Description of the Assuan protocol.

The architecture of the modular GnuPG system is based on several highly specialized modules which form a network of clients and servers. A common framework for intermodule communication is therefore needed and implemented as a library.

Goals:

• Common framework for module communication
• Easy debugging
• Easy module testing
• Extensible
• Optional authentication and encryption facility
• Usable to access external hardware

Design criteria:

• Client/Server with back channel
• Use a mainly text based protocol
• Escape certain control characters
• Allow indefinite data length
• Request confidentiality for parts of the communication
• Dummy module to allow direct linking of client and server
• Inline data or descriptor passing for bulk data
• No protection against DoS needed
• Subliminal channels are not an issue