I noticed this what I think is a bug.
So I have a blank regular Mifare Classic 1k 4 byte UID card with factory keys and factory access bits. I can read it fine on Flipper and I can update the value blocks too, no problem here.
However I can’t write new keys to the sector trailer with factory access bits set on the card.
I can verify that trailers can be written to by using the “Mifare Classic Tool” on Android by doing steps:
Read card → Edit dump and change only Sector 1 trailer keys A and B (leave data blank) → Write back to the card → Read card and see that the keys had changed.
I can also verify the keys had changed by reading with Flipper.
Now I format the card to return it to a factory state and do the same on Flipper:
Read → Save → Edit dump with Flipper Android app → Save and synchronize (also verify on the Flipper itself that the file is modified) → Write to Initial card
Then I get an error that not all sectors were updated.
Now I read the card again and sure enough the trailers are not updated.
Am I missing something or Flipper can’t actually write anything to trailers?