DESFIRE EV1 ChangeKey

[Jan Jan]

Everybody
I have some questions about the school DESFIRE EV1 cards
1.Can I use the single DES Key to authentication(0x0a),
then use changeKey(0xc4) to change master key to 3K3DES or AES?
if it can,How can i do.
2.How do I calculate the AES Key Version

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[mifaresdk]

Hi Jan,

A key version is a number notifying the current key. This number starts at 0 and you will increment it if the key value is changed. Usually this number is saved a part in your key store for bookkeeping.

The MIFARE Team

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[Jan Jan]

Thank you for your answer
Sorry I can not really understand the meaning of data
Let me ask it another way
If I write a program, and this program shows on this data field
How do I tell my clients, what is this and how to use it

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[mifaresdk]

Hi Jan,

Sorry I do not understand your request. Please let me know in which way you want to use the MIFARE DESFire EV1. Which kind of data should be saved on the card? What is your use-case?

Maybe we find a solution which fits your needs.

The MIFARE Team

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[Jan Jan]

Thank you for answering
Attachment file is an example of my program
I know that when I change KEY to DES or 3K3DES mode is not required KeyVersion
But when I change KEY to AES mode it is needed
I need to know this KeyVersion its role.
The "KeyVersion" It is just a number? (0x00 ~ 0xFF)
Or I can use "GetKeyVersion" command to get it, and then told the program used which one KEY to do authentication
or others

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[mifaresdk]

Hi Jan,

You can always call GetKeyVersion() without a previous authentication. With the ChangeKey() command the key version is updated.

The key version is important, if you have to update the card or issue a substitute card with a new key. It might be important in the service station which key – or in other words – which key version is used. But this depends on your particular implementation and which encryption method is used (e.g.: key diversification etc.).

The MIFARE Team

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[Jan Jan]

I think I should know how to respond to my clients
thank your very much

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[Ramu Pal]

I Want To Change Key Of Mifare Desfire Tag I Have Tried The Following Code But It shows Integrity Error !!


For Authneticate

desFireEV1.authenticate(0, IDESFireEV1.AuthType.Native, TWO_KEY_THREEDES,objKEY_2KTDES);

For Key Change
desFireEV1.changeKey(0, KeyType., SampleAppKeys.KEY_2KTDES, SampleAppKeys.NEW_KEY_2KTDES, (byte) 0);

Please Help Me Out for This Problem !!

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[TapLinx Support]

Hi Ramu,

Please have a look to this posts:

https://www.mifare.net/support/forum/topic/desfireev1-changekey-fail/

https://www.mifare.net/support/forum/topic/application-changekeysetting-integrity-error/

Here you will find an example how to changes keys.

The TapLinx team

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