Make GPB choosable for factory formatting

[Warborn123]

Hi, I just realised that when I try to do a factory format on a CUID Card (or Chinese magic card, gen 2), the last sector's access condition will become FF0780BC. I know the last last byte of the access condition is knid of useless, but I still don't understand why it is not FF078069. Thank you.

[ikarus23]

Hi! The 0x69 is in there because it refers to non-personalized cards according to AN10787 - MIFARE Application Directory (MAD). The "General-purpose byte (GPB)" might be different when a MAD is in use.

However, I'm not exactly sure, why the last GPB of a 1k MIFARE Classic card is 0xBC. I've never looked into MAD deep enough (it's on the todo list #30). I've just set it to 0xBC because factory new original tags by NXP had it set to 0xBC.

It's on 0xBC on other examples as well: http://nfc-tools.org/index.php/Libnfc:nfc-mfclassic.

[Warborn123]

Hi! The 0x69 is in there because it refers to non-personalized cards according to AN10787 - MIFARE Application Directory (MAD). The "General-purpose byte (GPB)" might be different when a MAD is in use.

However, I'm not exactly sure, why the last GPB of a 1k MIFARE Classic card is 0xBC. I've never looked into MAD deep enough (it's on the todo list #30). I've just set it to 0xBC because factory new original tags by NXP had it set to 0xBC.

It's on 0xBC on other examples as well: http://nfc-tools.org/index.php/Libnfc:nfc-mfclassic.

I actually never own any new NXP tags (since its NUID is not writeable), so I can't really check that myself. From what I saw MIFARE CLASSIC 1K/4K USER MANUAL Release 1.1.0 P.9, the last bit is for "user data", so it's kind of a strange choice to see 0xBC here (actually the 0x69 doesn't make any sense here either, now that I think about it, maybe its there to distinguish from Key B). Anyways, not important, maybe give us an option to chooe that if you have time. Thanks :)

[ikarus23]

Hehe, sure. But no promises. I feel that this is a rarely needed corner case ;) Also, the 0xBC seems to be the right state for factory formatted tags.