How to decrypt ISN from CAS3+ dump with а working key:
* Read the working key ID with Hitag2 compatible reader (1)
* Find the key number in the CAS3+ dump (2)
* Find the Crypto/ISK Low and High (3)
* Enter the Crypto/ISK Low and High to the Hitag2 compatible reader and read all key data (4)
* Copy PSW string (5) to some HEX calculator (6)
* Copy the "Pass" (7) from the CAS3+ dump to the HEX calculator (8)
* Calculate the XOR value (9)
* Do a "byte flip" (e.g. AA BB CC > CC BB AA) of the XOR value
* In a HEX calculator paste 6 times the byte flipped XOR value and remove the last 4 characters (10)
* Copy the encrypted ISN from the CAS3+ dump (11 )and paste it the HEX calc (12).
* The result of the XOR is the decrypted ISN.
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