DIMY Contact Tracing Protocol Simulator

A course project that translates privacy-preserving protocol concepts into an inspectable network simulator.

Problem / goal

The project needed to demonstrate how ephemeral identifiers, secret sharing, and Bloom filters interact while making protocol behavior and privacy assumptions observable.

My role

Protocol Security Developer on a course project, contributing mainly to frontend protocol logic, UDP communication, Shamir reconstruction, and Bloom-filter lifecycle.

My contributions

• Implemented rotating ephemeral identifiers, UDP broadcast behavior, TCP request-response flows, and Bloom-filter encounter storage.
• Implemented Shamir share reconstruction and coordinated threaded background loops with locks for protocol state.
• Implemented interactive protocol-node workflows and collaborated on multi-node integration checks.

Technical approach

• Modelled temporary identifiers, Shamir Secret Sharing, Bloom-filter encounter storage, UDP broadcasts, and TCP request-response communication.
• Used threading, locks, and background loops to coordinate node behavior, upload and query operations, and interactive commands.
• Integrated node behavior with teammate-owned backend and attacker components for protocol checks.

Key features

• Frontend nodes broadcasting and receiving temporary identifiers.
• Backend TCP upload and query workflows.
• Bloom-filter encounter-data lifecycle.
• Passive attacker model for inspecting protocol assumptions.

Impact / results

• Corrected Bloom-filter retention to enforce a six-filter limit, including the current filter.
• Made networking, concurrency, and privacy behavior inspectable through interactive commands and structured JSON messages.

What I learned

• Concurrency and protocol state must be designed together when behavior depends on timing and background work.
• An attacker model makes privacy assumptions easier to test and communicate.