Abstract

Mediator service is like a drop box / post box that Aries agents can use to receive and store encrypted messages in their stead.

Basic flow:

• people can send you messages at the mediator address if you are not always available to receive messages
• you can pick them up later from mediator service using pick up protocol

Mediator/ Agency are useful for scenarios like mobile phone agents which can't always receive messages. Due to reasons including:

• network interruption
• sleep /power off
• power conservation optimizations
  

There exist a agency/mediator service for Aries, but it has limitations:

• Written in NodeJS. A Rust based mediator service would be desirable for better integration with vcx
• Does not support pick up protocol (uses custom data exchange)
  

A new Rust based Aries mediator service would offer.

• High performance
• Horizontal scalability
• Simpler and more robust integration with Aries-vcx
• Support for newer standard protocols like Pick Up protocol.

Deliverables

Main Deliverables:

•  Specialized high performance Aries agent (mediator to-be) that can store "forward messages" received through connection protocol.
•  Pickup protocol data structs and impl inside aries-vcx
•  Mediator service that can answer pick up protocol requests to authenticated peers
•  CI to build and test on new commits.

Extra Deliverables:

•  CI to make releases based on tags and provide binaries or docker image in Github's release section.
•  (stretch goal): design/document mediator service component that can notify registered peers on inbox message available.

Project Plan

Stage 1: HTTP

...

Server 

•  Research and choose rust based web framework, suitable for project goals
•  Answerable HTTP end points to connect to service
•  Define storage traits and impl
•  Tests to ensure proper functioning of above features
•  CI: Build on commit/pushed commits.

Stage 2: Add data structures for Connection protocol to service

•  Load required modules from Aries-VCX and use in service to handle aries connections
• Implement simple http service with some endpoints
•  Include logging library (env_logger is popular choice)
•  Include E2E test - make request against the endpoints, expect appropriate response
•  CI: Lint, build, run & test each commit

Stage 2: Storage

•  Understand pick-up protocol specification
•  Based on the specification, design trait for retrieving messages and storing messages
•  Provide mysql implementation
•  Include integration tests
•  CI: Include new set of tests in CI

Stage 3: Integrate Aries-vcx

•  Include aries-vcx as project dependency
•  Initialize aries-vcx library (create wallet)
•  Add endpoint for clients to fetch connection invitation (built using aries-vcx)

Stage 4: Support establishing didcomm connections

•  Decide if there is need to alter storage traits, or to just create new implementations, and act accordingly.
  
•  Optimise endpoints (API etc) for with Aries connection and to handle multiple of them simultaneously
  
•  tests (see if data is being stored in database.)

stage 3: Add pickup protocol data structure to Aries-Vcx

•  Add data structures and maybe traits to Ariec vcx related to pickup protocol
•  (this could take time to design, iterate, and code inside vcx.). So break into sub-tasks as necessary.
  
•  Tests for above

Stage 4: Integrate included pickup protocol stuff in mediator code.

•   Pull pickup struct definitions / traits from vcx and integrate with local impl
•  see if additional local interfaces need to be defined for http / mediation (like accounts etc)
•  Tests.

Milestones

Eval1:
- setup development environment
- rust learning (learn and gain good pedagogical familiarity with concepts used: structs, impls, macros, etc)
- basic web service skeleton ready
- CI for making sure builds succeed

Eval2:
- Demonstrate grasp of basic rust concepts (mentioned earlier)
- Grasp understanding of more advanced rust concepts (arc etc)
- Able to use existing sophisticated/complex rust library inside a different project.

...

Eval4

...

•  Implement endpoint to fetch mediator's connection invitiation
•  Support establishing didcomm connection between client and mediator using aries-vcx Connection state machine
•  Create e2e test for establishing didcomm connection betwen test client and the mediator

stage 5: Receiving and storing didcomm messages

•  Enable receiving messages (mediation) on behalf of a connected client (which established connection and requested mediation - stage 4)
•  Add medaitor e2e test where mediator receives and stores didcomm message

stage 6: Add pickup protocol support

•  Add pick-up protocol data model to aries-vcx messages crate
•  Add pick-up protocol messages parsing to mediator
•  Add mediator e2e test performing message pick-up

stage 7: Bonus - websocket

•  Implement websocket interface for pickup protocol (think can be broken down further if we start working on this)

stage 8: Bonus - notifications

•  Implement pub/sub mechanism in distributed environment to assure instant notification of connected websocket clients about a newly received message (think can be broken down further if we start working on this)

Milestones

Evaluation 1 (July 11):

• Development environment setup
• Rust learning, http framework research
• Evaluation of Stage 1

Evaluation 2 (August 22):

• Evaluation of Stage 2, 3, 4

Evaluation 3 (October 6):

• Evaluation of Stage 5, 6

Evaluation 4 (November 14):

• Evaluation of Stage 7 / 8 or overall solution polishing&refactoring

Timeline

Future plans

Design and document ways in which websocket persistent connection based notification service could be integrated into mediator service project.

Benchmark the service.

Add support for did:peer:4 based did exchange.

Participants (Mentors/Mentees)

Mentors

Mentee

Processes

Internal communication and updates:

• • Slack is used for regular communications and updates
  • Weekly Zoom meetings are scheduled to discuss the progress, blocks, questions, advice
  • Biweekly mentee-mentee meetings for knowledge sharing, active collaboration.
    

Mentee maintains a blog with frequent updates:

•  Aries VCX Diaries

Other useful information can be found on this page

• Learnings and Deliverables - aries-vcx based Aries Mediator Project
• Links: Useful research, analysis and general guide.