Reply To: DESFire Xamarin

Forum MIFARE SDK DESFire Xamarin Reply To: DESFire Xamarin

Re: DESFire Xamarin

13. January 2020 at 10:31
Hi Jailah Mara,

To your first question. It is very difficult to give a detailed answer why in a multi block operation issues occurs between two Android versions. I know that available block sizes (for transport buffer) might vary between different middleware software versions. As a hint you should try to use the smallest block size and read only bytes you will really need. On a desktop operating system file data is always moved as minimal block size of 1K or 4K. But this is not true for Smartcard systems! Typically, the transport buffer sizes vary between 64 bytes to 256 bytes (including packet data). Block sizes larger than 256 is not supported by all driver/middleware drivers and you should avoid this size.

To your second question. The command “DeleteFile” of a MIFARE DESFire remove the occupied data but do not makes a memory cleanup! There is no “memory management system” on the card. The whole memory is released after a “FormatPICC” command. Please take in mind: a Smartcard allocates the required memory at creation time and use it for the life time of the product. You will never need the “DeleteFile” command except for the rare case if a feature for the card user has expired and will never be activated again.

The TapLinx team
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