Paper by Chris Culnane, Benjamin I. P. Rubinstein, and Vanessa Teague: “The subject of this report is the re-identification of individuals in the Myki public transport dataset released as part of the Melbourne Datathon 2018. We demonstrate the ease with which we were able to re-identify ourselves, our co-travellers, and complete strangers; our analysis raises concerns about the nature and granularity of the data released, in particular the ability to identify vulnerable or sensitive groups…..
This work highlights how a large number of passengers could be re-identified in the 2018 Myki data release, with detailed discussion of specific people. The implications of re-identification are potentially serious: ex-partners, one-time acquaintances, or other parties can determine places of home, work, times of travel, co-travelling patterns—presenting risk to vulnerable groups in particular…
In 2018 the Victorian Government released a large passenger centric transport dataset to a data science competition—the 2018 Melbourne Datathon. Access to the data was unrestricted, with a URL provided on the datathon’s website to download the complete dataset from an Amazon S3 Bucket. Over 190 teams continued to analyse the data through the 2 month competition period. The data consisted of touch on and touch off events for the Myki smart card ticketing system used throughout the state of Victoria, Australia. With such data, contestants would be able to apply retrospective analyses on an entire public transport system, explore suitability of predictive models, etc.
The Myki ticketing system is used across Victorian public transport: on trains, buses and trams. The dataset was a longitudinal dataset, consisting of touch on and touch off events from Week 27 in 2015 through to Week 26 in 2018. Each event contained a card identifier (cardId; not the actual card number), the card type, the time of the touch on or off, and various location information, for example a stop ID or route ID, along with other fields which we omit here for brevity. Events could be indexed by the cardId and as such, all the events associated with a single card could be retrieved. There are a total of 15,184,336 cards in the dataset—more than twice the 2018 population of Victoria. It appears that all touch on and off events for metropolitan trains and trams have been included, though other forms of transport such as intercity trains and some buses are absent. In total there are nearly 2 billion touch on and off events in the dataset.
No information was provided as to the de-identification that was performed on the dataset. Our analysis indicates that little to no de-identification took place on the bulk of the data, as will become evident in Section 3. The exception is the cardId, which appears to have been mapped in some way from the Myki Card Number. The exact mapping has not been discovered, although concerns remain as to its security effectiveness….(More)”.