SEPTENTRIO PolaRx5TR, Reference Manual

Page: 52 / 512

1 How To...
1.30 Use Galileo OSNMA
With the Open Service Navigation Message Authentication (OSNMA) feature, Galileo satellites
allow to verify the authenticity of navigation messages received from GNSS satellites, offering
a powerful means to detect and counter spoofing attacks.
In Septentrio receivers, OSNMA is used to discard untrusted satellites from the PVT compu-
tation. Three operating modes are supported:
off
where OSNMA authentication is disabled,
loose
where satellites are included in the PVT if they are successfully authenticated or if their
authentication status is unknown, and
strict
where only successfully-authenticated satellites
are included in the PVT.
In
strict
mode, the number of satellites available to the PVT may be limited as OSNMA does
not authenticate all visible satellites (e.g. only Galileo and GPS satellites depending on the
OSNMA service status).
After enabling OSNMA (in
loose
or
strict
mode), it typically takes a few tens of seconds to
a few minutes to authenticate messages. In
strict
mode, no PVT is computed during that time.
OSNMA is configured as follows:
1. Use the
setGalOSNMAUsage
command to enable OSNMA authentication. For exam-
ple, to enable OSNMA in
loose
mode, use:
setGalOSNMAUsage, loose <CR>
2. In strict mode, OSNMA authentication requires the availability of external time infor-
mation. In loose mode, this is optional but recommended for enhanced security. The
receiver can connect to an NTP time server for this purpose, as configured with the
setNTPClient
command. For example, to enable time retrieval from the default NTP
server, use:
setNTPClient, on, default
The receiver has been optimized for use with live Galileo signals. Necessary keys are em-
bedded into the software. For example the Galileo Merkle Tree root key, needed to enable
over-the-air reception of public keys, is known by the receiver, obviating the need for the user
to provide it.
Refer to section 2.6 for further details.
52