> as soon as you know who rented what bike
Except, as far as I can see, according to the article, the only required info is start and finish point and journey length.
Except, as far as I can see, according to the article, the only required info is start and finish point and journey length.
[1]: https://gawker.com/the-public-nyc-taxicab-database-that-acci...
1. The taxi medallions were extracted due to poor crypto choice (and simple structure of medallion IDs), so you can map from reality -> dataset
2. The celebrities were photographed entering/exiting the taxi, with the medallion captured.
If you broke the link -- the taxi medallion -- you wouldn't have de-anonymized trips. And NYC anonymization process clearly (and correctly) intended for that link to not exist.
That is, start, end and length was not the key motivators in de-anonymization in this case. However, you can still imagine this data is sufficient to de-anonymize when usage is rare (and you've captured either start or end destination), but otherwise, the taxi data is not indicative of anonymization futility but rather implementation failure.
In other cases, no photo is necessary (trips originating or ending at a residential address, linked to another sensitive location such as an abortion clinic).
There is a lot of research available on this topic. "Unique in the Crowd"[1], published in 2013, found that it takes only 4 GPS locations/timestamps to de-anonymize 95% of the population, with no other metadata. With 2 GPS pings, 50% of trips can be de-anonymized.