TfL is going to track all London Underground users using Wi-Fi

Discussion in 'London Underground' started by kevin_roche, 22 May 2019.

  1. kevin_roche

    kevin_roche Member

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    Last edited: 22 May 2019
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  3. swt_passenger

    swt_passenger Veteran Member

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  4. Bletchleyite

    Bletchleyite Veteran Member

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    Probably because TfL is generally seen to be trusted (and an organisation that has little to gain from "nefarious" use of the data), and because if you don't like it you can simply turn off your wifi.
     
  5. kevin_roche

    kevin_roche Member

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    I have no problem with the organisation knowing where I am but people always forget that your data can still get into the wrong hands. For example if you had a stalker who used it to follow you it might be of more concern.
     
  6. MikeWh

    MikeWh Established Member Senior Fares Advisor

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    The data will be immediately anonymised. There will be no way to assign a device to a person. They are purely interested in tracking trends of people using the network.
     
  7. Surreytraveller

    Surreytraveller Established Member

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    Surely they can use Oystercards and contactless to track trends?
    Or perhaps using WiFi to track people as well they can tell if people are using more expensive routes to complete their journeys than the Oyster system charges for?
     
  8. jellybaby

    jellybaby Member

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    Oyster or contactless tells TfL a passenger entered at Liverpool Street and exited at Victoria. It doesn't reveal if they took the Circle line or the Central+Victoria or another route.
     
  9. Surreytraveller

    Surreytraveller Established Member

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    That's what I was getting at
     
  10. jellybaby

    jellybaby Member

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    Fair enough, but it doesn't change the fare either way.
     
  11. MikeWh

    MikeWh Established Member Senior Fares Advisor

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    As the wi-fi data is anonymised they won't be able to match it to a specific Oyster card or CPC. TfL involved the Information Commisioner in the early stages of designing the system precisely to avoid any concerns later on.
     
  12. Surreytraveller

    Surreytraveller Established Member

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    Yes, I know. But they will probably track trends to see if people tend to use the routes they expect them to use. Is WiFi free on the Underground?
     
  13. NSEFAN

    NSEFAN Established Member

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    For the purposes of tracking where a device is, you don't have to connect to the WiFi. The access points can register that a device is nearby every time it scans for WiFi networks.
     
  14. codek

    codek Member

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    They did this a year ago and advertised it heavily.

    They even published the results. They did find people using weird routes. In response they concluded it was an education issue and the plan was better signage.

    They did also spot clever people taking seemingly longer routes that avoid congestion!
     
  15. WideRanger

    WideRanger Member

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    IKEA do the same for visitors in their stores (to monitor how people navigate the shop). I'm sure it must be pretty common.
     
  16. jellybaby

    jellybaby Member

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    Unless you enter or exit at Roding valley...

    I suspect that given enough data you could match WiFi MAC address tokens with Oyster/contactless data. If you were to look at all times my card was used across the network in a year and then looked at MAC address tokens seen at the same times I wouldn't expect many matches. Tokens that change everyday would prevent that but there may be other ways of joining the data up although maybe TfL want to know how routine travellers behaviour is different to occasional visitors?

    It would be nice if TfL provided details of their 'irreversible, one way pseudonymisation process'. It feels like something there should be an open industry standard for which can then get some proper scrutiny.
     
  17. kevin_roche

    kevin_roche Member

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    There are several standard ways to do this. SHA-1 or SHA-256 for example are well known one way processes. Unfortunately they are not completely unbreakable since they could be broken with rainbow tables. The use of the Salt helps as long as nobody knows what it is.
     
  18. jellybaby

    jellybaby Member

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    I'd call those Secure Hash Algorithms. TfL apparently used a hash algorithm in the 2016 trial but this 'has been replaced with a system of tokenisation' (https://www.wired.co.uk/article/london-underground-wifi-tracking) which implies they are doing something else.
     
  19. frediculous

    frediculous Member

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    Don't forget most smartphones utilise MAC address tumbling so the displayed address will change every day, if not more.

    Lots of places do this: airports and shopping centres to name two.
     
  20. Ken H

    Ken H Established Member

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    there is a technique know as 'jigsawing' This is where you take several databases from different sources and try and make matches to build up a profile of a person.
    So even if you only have a small amount of data about a phone, you may well be able to join it to another database...
     
  21. robert7111a

    robert7111a Established Member

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    I will ensure that my wi-fi is switched off on my mobile devices
     
  22. jellybaby

    jellybaby Member

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    Apparently they only do that when sending out probes, not when joined to a network.

    https://tfl.gov.uk/corporate/privacy-and-cookies/wi-fi-data-collection?cid=wifi-data-collection

     
  23. rebmcr

    rebmcr Established Member

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    Encryption is nothing to do with anonymisation.

    Unless two MAC addresses collide to the same hash (which by design of hashing algorithms is vanishingly unlikely) the record of an individual's movements are effectively unchanged, no matter whether the person tracking them is seeing the bare MAC address, or the 1:1 associated hash. Salting will similarly have zero impact on this, unless it causes the aforementioned practically-impossible collision.
     
  24. kevin_roche

    kevin_roche Member

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    You are correct. There is no need to know someones MAC address the hash would work equally well.
     
  25. thejuggler

    thejuggler Member

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    If I was a regular user knowing how busy each service is is useful. If the service arriving is rammed, but the next one 2 minutes behind is half empty I would know to wait.

    As a visitor knowing which route to take based on typical loadings (not on what I think is the most direct route) at the time I am travelling would also be useful.
     
  26. Mojo

    Mojo Administrator Staff Member Administrator

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    London Underground already has this information on the automated lines, and it comes from a more reliable source than Wifi, but I’m not sure it’s included in the information given out publicly on their APIs. You could always ask a friendly member of staff if they have an iPad.
     

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