Re: [89attendees] Oyster card balance

Stefan Winter <stefan.winter@restena.lu> Wed, 12 March 2014 06:47 UTC

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Date: Wed, 12 Mar 2014 07:46:40 +0100
From: Stefan Winter <stefan.winter@restena.lu>
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Subject: Re: [89attendees] Oyster card balance
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Hi,

> The answer is both; it's like a banking system, doing
> increments/decrements, with an overdraft buffer and a resolution
> mechanism.

Well except that your bank always has an authoritative view on your
balance; if the Oysters don't phone home every time there is no such
central view.

I understand the card is offline until "synchronised" at a resolution
tube station?

So one could tamper with the balance arbitrarily so long as one avoids
travelling through those stations?

Stefan

> 
> On Tue, Mar 11, 2014 at 1:17 PM, Ted Lemon <mellon@fugue.com> wrote:
>> The Oyster card system knows what transactions have occurred on the oyster card, and can tell you the balance without the card being present.   So I think the balance is stored in the database, not the card, although it may be that the card is used as a backup in case of network partition.   I suspect tampering would be quickly detected (it's certainly easy to detect in principle the way the system is set up) and hence not advisable for those of us who wish to be able to continue attending IETF in person.
>>
>>
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Stefan WINTER
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