Disposable Mifare Ultralight

[onyekachi]

Please, I am new with Ultralight, most of my work/experience has been with DesfireIV. Please help me understand how Ultralight works
1> like Desfire, am I able to change the key from defulat key?
2> Can I write to it? how do I determin how many times I can write to it (if it has limitaion - I see about the OTP)
3> What is the intended use of the counter? I see how to increment it but why would you need that (pardon the ignorance)

Thanks for your support MifareSDK support is great

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[mifaresdk]

Hi Onyekachi,

Please take in mind: the DESFire EV1 is a security product, but the MIFARE Ultralight it is not! Of course, there are the possibility to protect pages on the Ultralight with a key, but you cannot compare this feature with the key management on a DESFire EV1.

The OTP counter allows for instance a ticket application the usage of a limit time. Each time the ticket is used, the OPT set one bit to 1. After an amount of usages the ticket cannot be used anymore because the bits cannot be reset to 0. Please note, the Ultralight is used very often in “paper tickets”.

Regards,
The MIFARE Team

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[onyekachi]

Thank you very much for your response - but does Ultralight provide me the capability to initialize (Set) the number of counters (bit). Can I set the counter to 0000 or 0010 myself, or is it pre-set?

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[mifaresdk]

Hi Onyekachi,

Yes, you can set the count to any value, but you never can set a bit to 0 again if it was 1 before. Please take in mind, the counter is in function a “bit counter”.

For instance, you allow a user the usage of five times to use the ticket. Then you will set the counter to the initial value “11111…11100000”. At every usage you will set a “0” to “1”. If the OTP counter is “11111…111”, it cannot be used again.

Regards,
The MIFARE Team

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