Unidirectional Atomic Messaging via Shared Memory Buffer
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Solution Overview
Problem
Conventional multilevel security systems face challenges in ensuring secure, unidirectional communication across different security classification levels, often relying on air gaps or one-way memory that lacks feedback, leading to potential security vulnerabilities and incomplete message transmission.
Innovation Solution
A shared memory system is implemented, allowing the message producer to have read/write access while the consumer has only read access, with a writer counter ensuring atomic receipt of messages by preventing acknowledgement from the consumer, thus ensuring that messages are received in entirety or not at all, and using indices and counters for asynchronous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If unidirectional communication is implemented without feedback mechanisms, then security requirements are satisfied, but message transmission reliability deteriorates
Solution Approach 1:
An intermediary buffer memory is introduced between the producer and consumer to enable indirect communication. The buffer stores messages atomically, allowing the producer to write messages without requiring acknowledgment from the consumer, while ensuring reliable delivery through the buffer's atomic store operation.
Solution Approach 2:
Implicit feedback is provided through the buffer's acknowledgment mechanism. When the producer successfully stores a message in the buffer, it receives implicit confirmation of successful transmission without requiring explicit feedback from the consumer, thus maintaining unidirectional communication while ensuring reliability.
2Reliability
If atomic message delivery is ensured without consumer acknowledgment, then security is maintained, but communication reliability worsens
Solution Approach 1:
The buffer memory performs self-service by automatically ensuring atomic delivery of messages. The producer simply writes to the buffer, and the buffer's inherent atomic store operation guarantees that the entire message is delivered or not at all, without requiring complex coordination or acknowledgment protocols between producer and consumer.
3Reliability
If shared memory is made accessible for write by producer only, then security threshold is enforced, but communication feedback capability deteriorates
Solution Approach 1:
Asymmetric access control is implemented where the producer has write access to the buffer while the consumer has only read access. This asymmetric permission structure enforces unidirectional communication and prevents the consumer from modifying or corrupting messages, while still allowing the producer to reliably deliver messages through the buffer.
Data Source
AI summary
A shared memory system for providing unidirectional communication across a security threshold defined by producer and consumer of a message at different security levels. A unidirectional shared memory element is accessible for read and write access by the message producer (sender), and the consumer (receiver) has only read access. Transmission logic ensures atomic receipt of the message if it is received, as the receiver cannot issue an acknowledgement to the sender as in conventional electronic interfaces. An arrangement of indices and counters allows asynchronous operation by the sender and receiver, as messages may queue up in the shared memory if the producer exceeds the consumer. In the event of a failure, anomaly, or resource overrun, it is known that messages that were received were received in entirety; in other words, atomicity is preserved.