Packet Acknowledgement And Timing; Encryption; Ms Method - VeriFone MX800 series Programmer's Manual

IPP MS DUKPT C
AND OMMUNICATIONS
Packets
Packet
Acknowledgement
and Timing

Encryption

278
M X 800 S P
ERIES ROGRAMMERS
P
ACKETS
The IPP only responds to commands that have the proper packet format. The
packet can be in the form of <STX>msg<ETX>[LRC]or <SI>msg<SO>[LRC]
according to the specific command.
The IPP returns <ACK> within 20ms to the terminal when it receives a properly
framed packet with a valid LRC. When other framing is received for a command
that requires <STX><ETX> framing (for example, <SI><SO>, <SI><ETX>, or
<STX><SO>), <ACK> is returned if the LRC is valid; only the specified framing is
processed.
This rule also applies to <SI><SO> packet commands. The IPP does not act on
an incorrectly formatted packet. This includes a packet with a wrong header,
wrong trailer, wrong field separator, an out of range indexing, or incorrect packet
length. An example of a packet that has an out of range indexing would be
packet 02, master key address = 15.
The response message from the IPP follows the <ACK> if the packet command
has a response. However, the timing varies from different commands.
There are two methods of PIN encryption in IPP:
•
MS
•
DUKPT

MS Method

IPP encrypts the customer's PIN according to the ANSI X9.8 standard and the
ANSI X9.24 master key management method, based on the ANSI X3.92 DES
algorithm implemented in the IPP firmware. The encryption during a transaction is
as follows:
1
The master device sends a private communication key (or working key) to the
IPP, where it is decrypted using the currently selected master key. An account
number and PIN are also entered to IPP through the master device.
2
The IPP generates the clear text PIN block using the account number and
PIN.
3
Using the decrypted working key, the IPP encrypts the PIN block using the
DES algorithm and working key, then sends the encrypted PIN block to the
master device.
4
The master device appends the encrypted PIN block to a request packet and
forwards the completed request packet to the host.
G
UIDE