Red Hat CERTIFICATE SYSTEM 8.0 - ADMINISTRATION Admin Manual page 265

Configuring Flat File Authentication
6. Save the edits.
9.2.4.2. Editing flatfile.txt
The same flatfile.txt file is used to authenticate every SCEP enrollment. This file must be
manually updated every time a new PIN is issued to a router, assuming that the router contacts the CA
directly.
By default, this file is in /var/lib/pki-ca/conf/ and specifies two parameters per authentication
entry, the UID of the site (usually its IP address, either IPv4 or IPv6) and the random PIN generated by
the RA.
UID:192.168.123.123
PIN:HU89dj
Each entry must be followed by a blank line. For example:
UID:192.168.123.123
PIN:HU89dj
UID:12.255.80.13
PIN:fiowIO89
UID:0.100.0.100
PIN:GRIOjisf
243