User's Manual

FILE AUTHENTICATION
Introduction to File Authentication
84 VX 675 REFERENCE GUIDE
It is not mandatory to always download a signature file and its target application
file at the same time. For example, you can download the corresponding signature
file in a separate operation. A non-authenticated application can reside in the
terminal memory, but is not authenticated or allowed to run on the terminal until
the signature files for the application executable files are processed by the file
authentication module after a subsequent download procedure and terminal
restart.
Determine Successful Authentication
To ensure the VX 675 terminal’s logical security, never assume that a target file
was authenticated simply because it was downloaded to the VX 675 terminal
together with its signature file.
There are several ways to ensure a target file is successfully authenticated after a
download:
• Confirm if all downloaded executable files run. If an executable code file is
not successfully authenticated, the operating system does not allow it to
execute and run, either following the initial download or on subsequent
terminal restarts. The effect of this rule depends on whether or not all
executable files are successfully authenticated.
• If the executable file that failed to authenticate is the main application
(*.out) specified in the CONFIG.SYS *GO variable, the main application
is not allowed to run.
• If the executable that failed to authenticate is a secondary executable
(*.out) or shared library (*.lib) used by the main application, the
CONFIG.SYS *GO application executes and runs until it issues a function
call to that library. When the main application attempts to access a non-
authenticated executable, the main application may crash.
• Visually (and audibly) confirm file authentication during the process.
When the file authentication module is invoked at terminal restart and detects
a new signature file, it displays status information on the screen indicating
success or failure of the authentication of each target file based on its
corresponding signature file. (A similar status display also appears on the
screen when you download digital certificates.)
You can watch the screen display following the download to see if a specific
target file fails authentication. If this happens,
FAILED is displayed for five
seconds on the screen below the filenames of the target and signature files,
and the terminal beeps as an alert.
An application program can issue a function call to read the ATTR_NOT_AUTH
bit’s current value for all relevant files to verify they were successfully
authenticated. If the ATTR_NOT_AUTH bit’s binary value is 1, the file did not
authenticate; if 0, the file did authenticate.