  Digitisation is often viewed as beneficial to a user. Where originally 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. While these actions may seem functionally identical to their
analogue counterparts, they come with one important difference. Namely, in the
digital case, a user's actions are automatically recorded. The recording of
user's interactions presents a problem because this information can be used
outside the control of the person whom it concerns. This issue is only
exacerbated by the centralisation of these aforementioned services'
authentication mechanisms permitting the collection of even more data. This
work aims to motivate the need and establish the feasibility for the
application of a privacy-enhancing digital token management service to public
transit. A proof-of-concept implementation of the Decentralised Digital
Identity Architecture proposed by Goodell and Aste is developed. This
implementation was optimised for the public transport use case. Finally, its
performance is tested in a local environment to better understand the technical
challenges and assess such a system's technical feasibility in a production
setting. It was observed that for loads between 1 and 5 requests per second the
proof-of-concept performs within acceptable limits with a maximum median
response time of 438 milliseconds. Above 5 requests per second response times
drastically increase due to hardware bottlenecks. It was concluded that the
demonstrated throughput and latency shows that the system can feasibly compete
with solutions currently in use. Yet, further work is needed to demonstrate
these performance characteristics in an environment similar to that experienced
in production.

Computers and Society;Cryptography and Security