Monday, October 20, 2014

This is tomorrow...

On October 21, 2014, the U.S. Coast Guard (USCG) will conduct AIS test messaging from all
USCG NAIS base stations located across the United States; for up to 15 minutes on the hour,
from 1100-2215 UTC. These messages can be identified by their Maritime Mobile Service
Identity (MMSI) number: 003669139 or 00366613 and by the words ‘USCG TEST’ within their
contents. This is the first of many tests the USCG will conduct in the future as it seeks to provide
another timely delivery source of navigational information and services to promote safety,
efficiency, and integration of the Marine Transportation System (MTS).
Messages to be tested: AIS Application Specific (ASM) messages 8, 25, and 26, with DAC = 001,
367, FI’s = 0, 22, 29, 33, or 35; AIS Safety Related Text (SRM) messages 14, of various lengths,
using repetitions of the text ‘USCG TEST’. For further information on AIS messages, DACs, and
FI’s visit
Mariners capable of decoding these messages can ignore them and should contact the USCG
Navigation Center at 1-703-313-5900 or should they encounter any
negative impacts due to the testing.

Wednesday, October 15, 2014

Encrypting non-military/law enforcement AIS is a bad idea

It was recently brought to my attention that some high level people are proposing that the IMO require a class of civilian (aka not military or law enforcement) vessels to use encrypted AIS to broadcast their position.  This is an absolutely terrible idea.

Having ships broadcast their location encrypted defeats the primary safety aspect of AIS for those vessels, the encrypted messages do not expose their slot usage and thereby drastically increase the number of packet collisions in a local area (decreasing safety for normal AIS traffic), and encryption key management is not work well of large population of mariners.  It would be a disaster in safety, technical and political terms.

The traditional "blue force" AIS units are just class A devices with slightly modified software (I own one).  There really shouldn't be any cost difference.  You could also change the programming for class B devices and have them transmit the encrypted position messages, but please don't do that.