Intel MEBX User Guide for Intel 7 Series Chipset

Intel® ME Manageability Features

Appendix D: PID-PPS Checksum

The PID and PPS are made up of ASCII codes of some combination of

characters – capital alphabet characters (A–Z), and numbers (0–9).

• The PID is an eight character entry of the form: XXXX-XXXC (where "C"

is the CRC (Cyclic Redundancy Check) of the preceding characters) and is

sent in the open.

• The PPS is a thirty-two character quantity of the form:

XXXC-XXXC-XXXC-XXXC-XXXC-XXXC-XXXC-XXXC (where "C"

is the CRC of the preceding characters) and is a secret shared between the

Intel AMT device and the Setup and Configuration Server.

When the PID and PPS are entered via the MEBx sub menu/USB key, the

firmware checks for checksum characters embedded in the values. The last

character of the PID is expected to be a checksum of the previous seven

characters, and the fourth character in each group of four characters in the PPS

is expected to be a checksum of the previous three characters. This check is

made to reduce the possibility of operator error when entering these values.