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

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.

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

Week	Activity	Status
June 1 - June 30	Onboarding, research, rust learning
July 1 - July 11 Evaluation 1	Stage 1 (server)
July 11 - July 25	Stage 2 (storage)
July 26 - August 2	Stage 3 (aries-vcx as dependency)
August 3 - August 22 Evaluation 2	Stage 4 (didcomm connections)
August 23 - September 5	Stage 5 (Receiving&storing didcomm messages)

September 6 - October 3 Evaluation 3	Stage 6 (Add pickup protocol)
October 4 - November 14 Evaluation 4	Refactoring / Stage 7, 8 / Other improvements / catch-ups

Future plans

Design and document ways in which 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

Name	Hyperledger Discord	Affiliation

Name	Hyperledger Discord	Affiliation
Patrik Stas	Patrik Stas#7722	Absa Group
Bogdan Mircea	bobozaur#5997	Absa Group
Miroslav Kovar	mirgee#3763	Absa Group
George Mulhearn	gmulhearn#0356

Mentee

Name	Email

Name	Email
Naian G	ng.p.ref+hlfwiki@mailbox.org

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

Project Plan - aries-vcx based message mediator service