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A Decentralised Digital Token Architecture for Public Transport

Oscar King, Geoffrey Goodell

TL;DR

This work aims to motivate the need and establish the feasibility of the application of a privacy-enhancing digital token management service to public transit, and develops a proof-of-concept implementation, which demonstrates throughput and latency indicate that the system can feasibly compete with solutions currently in use.

Abstract

Digitisation is often viewed as beneficial to a user. Whereas traditionally, people would physically have to identify to a service, pay for a ticket in cash, or go into a library to access a book, people can now achieve all of this through a click of a button. Such actions may seem functionally identical to their analogue counterparts, but in the digital case, a user's actions are automatically recorded. The recording of user's interactions presents a problem because once the information is collected, it is outside of the control of the person whom it concerns. This issue is only exacerbated by the centralisation of the authentication mechanisms underpinning the aforementioned services, permitting the aggregation and analysis of even more data. This work aims to motivate the need and establish the feasibility of the application of a privacy-enhancing digital token management service to public transit. A proof-of-concept implementation is developed, building upon a design proposed by Goodell and Aste. This implementation was optimised for the public transport use case. Its performance is tested in a local environment to better understand the technical challenges and assess the technical feasibility of the system in a production setting. It was observed that for loads between one and five requests per second the proof-of-concept performs comparably to other contactless payment systems, with a maximum median response time less than two seconds. Due to hardware bottlenecks, reliable throughput in our test environment was limited to five requests per second. The demonstrated throughput and latency indicate that the system can feasibly compete with solutions currently in use. Yet, further work is needed to demonstrate their performance characteristics in an environment similar to that experienced in production.

A Decentralised Digital Token Architecture for Public Transport

TL;DR

This work aims to motivate the need and establish the feasibility of the application of a privacy-enhancing digital token management service to public transit, and develops a proof-of-concept implementation, which demonstrates throughput and latency indicate that the system can feasibly compete with solutions currently in use.

Abstract

Digitisation is often viewed as beneficial to a user. Whereas traditionally, people would physically have to identify to a service, pay for a ticket in cash, or go into a library to access a book, people can now achieve all of this through a click of a button. Such actions may seem functionally identical to their analogue counterparts, but in the digital case, a user's actions are automatically recorded. The recording of user's interactions presents a problem because once the information is collected, it is outside of the control of the person whom it concerns. This issue is only exacerbated by the centralisation of the authentication mechanisms underpinning the aforementioned services, permitting the aggregation and analysis of even more data. This work aims to motivate the need and establish the feasibility of the application of a privacy-enhancing digital token management service to public transit. A proof-of-concept implementation is developed, building upon a design proposed by Goodell and Aste. This implementation was optimised for the public transport use case. Its performance is tested in a local environment to better understand the technical challenges and assess the technical feasibility of the system in a production setting. It was observed that for loads between one and five requests per second the proof-of-concept performs comparably to other contactless payment systems, with a maximum median response time less than two seconds. Due to hardware bottlenecks, reliable throughput in our test environment was limited to five requests per second. The demonstrated throughput and latency indicate that the system can feasibly compete with solutions currently in use. Yet, further work is needed to demonstrate their performance characteristics in an environment similar to that experienced in production.

Paper Structure

This paper contains 22 sections, 2 equations, 3 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Problem Statement
  3. Research Objectives
  4. Chapter Structure
  5. Background
  6. Societal Context
  7. Distributed Ledger Technology and Associated Terminology
  8. Privacy-Enhancing Identity Management Systems
  9. Related work
  10. Adapting the Architecture for Transport for London
  11. Protocol Explanation
  12. Technical Tradeoffs
  13. Implementation
  14. Testing Methodology
  15. Results
  16. ...and 7 more sections

Figures (3)

  • Figure 2: A schematic representation of the interactions involving a passenger when entering or exiting the transport system.
  • Figure 3: The throughput of the two test cases for which the measured median latency was over 500 milliseconds in the maximum load scenario.
  • Figure 4: Time taken to generate a single blind signature.