DESFire EV1 Reset to factory default

[SheldonM]

Good day,

I would appreciate if someone could shed some light on formatting DESFire EV1 cards back to factory default (Uninitialized / Un-Personalized State).

My format function seems to work except that the card crypto is still AES.

These are my steps:
1. Select PICC Master app - 0x000000

2. Authenticate PICC Master Key - DesAuth(KEY0, MY_MASTER_KEY, MY_KEY_VERSION)

3. DesFormat(0xFC)

DONE

By doing the above should the DESFire EV1 card not be back in factory default state?
The default key which is 00..00 works to access the card after the format function except that the Crypto still in use is still AES and not DES.

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[TapLinx Support]

Hi Sheldon,

The datasheet explains the behavior of the FormatPICC command. The PICC Master Key which is required before you can use the format is NOT changed also the PICC key settings are NOT changed.

The TapLinx team

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[SheldonM]

Thank you. I noticed that. The formatting works as I can verify that the cards contents is empty.

Can the card encryption type be set back to DES from AES?

The datasheet doesn't appear to be very clear on this.

I found DES to AES, DES to DES, AES to AES but nothing on AES to DES.

Or if has has been changed to AES will it be no longer possible to revert back to DES when trying to restore back to factory state?

Thank you for your time and effort.

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[TapLinx Support]

Hi Sheldon,

Of course, you can set the PICC Master Key to the factory settings if you change the current key to the default key and change the cipher from AES to 2K3DES (called native).

For me it makes no sense to do that, except for training purposes. As an issuer you should change the default cipher only once from 2K3DES to AES and never change it back. 2K3DES is a weak cipher and the factory settings are only for compatible reasons to the early DESFire product.

Regards,
The TapLinx team

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[SheldonM]

Hi Support,

The main reason I'm trying to do this is to have 4000 cards back in default factory state that have been personalized mistakenly with the wrong app and keys.

They were meant to be used on an older system that is different to what we have now as I don't have the capacity to develop a legacy app that would be compatible with the other system. The older system also doesn't have all the required source available so I don't even know where to start.

But having the cards back in factory default would solve the immediate issue for me.

Thanks for all your time and help so far.

Regards,
Sheldon

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[André Bertrand]

Hello,
I have exactly the same problem, did you find a solution?

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[TapLinx Support]

Hi André,

The solution is explained in this post. The format command removes all applications and release all occupied memory. But the PICC Master Key is untouched! If you want to bring this also in the “default state”, you must change the key value to zero and key type to 2K3DES.

The TapLinx team

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