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User Manual, SecureHead USB and UART Interface
Activation Challenge Reply Command
This command serves as the second part of an Activate Authentication sequence. The host sends
the first 6 bytes of Challenge 1 from the response of Activate Authenticated Mode command, two
bytes of Authenticated mode timeout duration, and eight bytes Session ID encrypted with the result
of current DUKPT Key exclusive- or’ed with <3C3C 3C3C 3C3C 3C3C 3C3C 3C3C 3C3C
3C3C>.
The Authenticated mode timeout duration specifies the maximum time in seconds which the reader
would remain in Authenticated Mode. A value of zero forces the reader to stay in Authenticated
Mode until a card swipe or power down occurs. The minimum timeout duration required is 120
seconds. If the specified time is less than the minimum, 120 seconds would be used for timeout
duration. The maximum time allowed is 3600 seconds (one hour).
Session ID information is included. If the command is successful, the Session ID will be changed.
The Activate Authenticated Mode succeeds if the device decrypts Challenge Reply response
correctly. If the device cannot decrypt Challenge Reply command, Activate Authenticated Mode
fails and DUKPT KSN advances.
Command Structure
Host -> Device:
<STX><S><82h><10h><Activation Data><ETX><CheckSum>
Device -> Host:
<ACK> (success)
<NAK> (fail)
Activation Data: 16 bytes, structured as <Challenge 1 Response> <Session ID>
Challenge 1 Response: 6 bytes of Challenge 1 random data with 2 bytes of Authenticated mode
timeout duration. It’s encrypted using the key derived from the current DUKPT key.
Session ID: Optional 8 bytes Session ID, encrypted using the key derived from the current DUKPT
key.
Deactivate Authenticated Mode Command
This command is used to exit Authenticated Mode. Host needs to send the first 7 bytes of
Challenge 2 (from the response of Activate Authenticated Mode command) and the Increment Flag
(00h indicates no increment, 01h indicates increment of the KSN) encrypted with current DUKPT
Key exclusive- or’ed with <3C3C 3C3C 3C3C 3C3C 3C3C 3C3C 3C3C 3C3C>.
If device decrypts Challenge 2 successfully, the device will exit Authenticated Mode. The KSN
will increase if the Increment flag is set to 01h. If device cannot decrypt Challenge 2 successfully,
it will stay in Authenticated Mode until timeout occurs or when customer swipes a card.