This follows the same approach as when you first uploaded mobile pass key files.

1. Save each of the DESFire application keys you need to use in a file, with the name appkey#.txt, where # is replaced with a number from 1 to 9. Each text file should just contain one DESFire application key with 32 hex digits, for example, key=bd6a15d1039e7527edfd01f37a220f3e

   Note: A VTAP reader cannot use more than 9 application key files.

2. Load your keys by copying these files onto your VTAP reader. Just connect your VTAP reader to a PC via USB, so it appears as a mass storage device on the PC file system (unless disabled or locked), then you can drag and drop the files.

   

   Alternatively, transfer the file to your VTAP reader using Zmodem to transfer over a serial interface.

3. Power cycle your VTAP reader. (Disconnect or safely remove the drive from the PC then reconnect it.) When you reboot the VTAP reader your key will have been stored in hardware, and will no longer be listed as a file on the device.

   Alternatively, send a ?KEYLOAD command over a serial interface for the key to be loaded, to avoid the need to restart the VTAP reader.

1. Open the file config.txt in a text editor (such as Windows Notepad).

2. Add lines to the file config.txt, using your own Application ID, File ID and Key Number. If there is already a line reading NFCType4=U, instructing the VTAP reader to read only the UID of DESFire cards, you will need to overwrite that line with the new content.

   Note: The VTAP reader expects the DESFireAppID to be a 24 bit number formatted as 6 hex digits with the most significant byte first. However, some vendors and software treat the Application ID value as a byte sequence with the least significant byte first, which is the byte order used in communications with the card. If the VTAP reader fails to read your DESFire card application, try reversing the order of the DESFireAppID bytes. For example, if DESFireAppID=F56400 try DESFireAppID=0064F5.

   Two examples follow, the first where the DESFire data is securely held and requires keys, and the second without cryptography or a DESFire format.

   Example: Settings in config.txt to read secured data from DESFire cards or tags

   Copy

   !VTAPconfig
   
   NFCType4=D          ; Read NFC Type4 cards as DESFire
   DESFireAppID=F56400 ; 24 bit value (6 hex digits)
   DESFireFileID=1     ; File ID within application (decimal 0 to 255)
   DESFireCrypto=3     ; 0 = None; 1 = 3DES; 3 = AES (default)
   DESFireKeyNum=1     ; Application key number used for authentication
   DESFireKeySlot=1    ; Application key slot number on VTAP
                       ; here use appkey 1
   DESFireFormat=1     ; How to interpret the data
                       ; =0 no format
                       ; (set DESFireReadLength and TagReadFormat)
                       ; =1 KEY-ID format (26 bit facility code 
                       ; and number, H10301 compatible)

   If DESFireCrypto=0 (no cryptography) or DESFireKeySlot=0 (no key), there will be no authentication or file communications encryption. This will allow unrestricted, plain text file access to some application data, only if this is permitted by the DESFire card configuration.

   When DESFireFormat=0, you can further control the output by using the settings:

   • TagReadFormat - to output the payload in either hex (=h, default), ASCII (=a) or decimal (=d).

   • If ASCII is set, each byte is an ASCII character.

   • When decimal is set, the VTAP reader will interpret binary data as a 64 bit decimal value and output ASCII decimal digits. In this case TagReadLength should not exceed 4 bytes.

   • For hexadecimal, the VTAP reader will convert binary data to ASCII hex digits with 2 digits per byte.

   • TagWiegandBits - to set the number of bits output over the Wiegand interface (=1 to 255), where the default is 0, or for automatic detection of bits available use =0 value.

   Example: Settings in config.txt to read data from DESFire cards or tags without cryptography or DESFire format

   Copy

   !VTAPconfig
   
   NFCType4=D
   DESFireAppID=2308A1
   DESFireFileID=48
   DESFireCrypto=0     ; No cryptography
   DESFireFormat=0     ; No format, so must set DESFireReadLength and
                       ; TagReadFormat    
   DESFireReadLength=8 ; Number of bytes to read if DESFireFormat=0
   TagReadFormat=a     ; Output payload in ASCII format, with each byte 
                       ; interpreted as an ASCII character
   TagWiegandBits=64   ; Set the Wiegand output bit length to 64

    

3. Save the amended config.txt file and these changes will take effect immediately.