J.M.’s point  about having an agreement with your team about what to wear when you are approaching a team compound so you can be recognized as belonging to part of a team brought up a very good point that I think deserves closer examination. Basically what J.M. is talking about is a method of authentication. He also did bring up some of the weak points of using this as authentication, such as if you get commonly available camouflage will someone be able to infiltrate? Let’s take it a step further. What if you get extremely custom one-of-a-kind camouflage and you feel that you can rely on it, and then one of your team mates gets captured, killed, or loses their gear? Now do you feel that method of authentication is still reliable, when people might be able to get even closer without raising an alarm? My point is think about your methods of authentication. There are three factors of authentication, which are: 1) Something you know, 2) Something you have, and 3) Something your are. We should take these into account as we establish our SOPs (Standard Operating Procedures), both for initial approach to the post as well as when returning from patrol or hunting/foraging. Also, keep in mind, not only should there be a method for folks approaching the retreat to authenticate themselves to those already there, there should also be a way that the occupants of the retreat can authenticate themselves to those approaching and indicate that it is safe to come in. So what are some ideas that could be used? Something you know: You could use a challenge and a password such as the D-Day Flash! Thunder! (Keep in mind there was a backup for that with the little cricket clickers the GIs were issued.) The downside of this is someone could overhear and compromise the password. You could make this more complex by having a date or weather-related password rotation. You could use a flashlight to send a specific series of long and short flashes. It could be actual Morse code but does not have to be. You could have a specific hand signal or a way to carry your gear.
To authenticate a “safe to approach/ friendly occupied post” you could open the shutters of a specific window or place a specific blanket on a clothes line. Certain folklore states that certain patterns of quilts on clothes lines were used as signals for the underground railroad. This was debunked by quilt scholars in the 1990s, but just because it’s not historically true does not mean it’s not a good idea. So what other signals could you hide in plane sight? What about one that states it’s unsafe to approach and meet at rally point A? Just think this out and see what other things you could come up with for signals for authentication?
How about something you have?
Well that custom pattern of uniform is something you have, but we already saw how that could be compromised. What else could you do with something you have? What about combining something you have with something you know? Now if the uniform is stolen, they might not get the full authentication procedure, which will help alert your team mates. So you could take the flashlight signal and change that to a specific colored laser issued to everyone. Now okay, if the laser is stolen, they might not know it’s an authentication tool. Even if they know that, now they have to know to approach a specific part of the retreat with a specific on/off pattern.
You could take the uniform idea and add the knowledge that you must approach the post with your hat off in your left hand with your right pant leg bloused into the boot and the left one hanging free. It looks silly, but who would think to do that if they stole your uniform and learned of the retreat location?
I think that something you are, while an effective (yet not fool proof and in many cases able to be faked) tool in today’s times, I don’t think this will be the most reliable means of authentication in a TEOTWAWKI situation. Electronic biometrics are expensive, can be fragile, and power for them might not be available. Plus, in most cases, the subject has to be closer than you would want them to be if you were not sure who it is that is approaching your retreat. You might say, how about keeping pictures of all of the team mates? There are two problems with this. First, I would make sure you had them as part of your emergency destruction SOP, if you got overrun. For the second problem, imagine this scenario. You have a somewhat chubby, pale, clean-shaven team mate who is stuck 500 miles away from the retreat when SHTF. He ends up having to spend quite a while roughing it and hoofing it to the retreat. What are the chances he is going to look like his picture or how you remember him when he gets there? This is why I say, while there are three factors of authentication, I would prefer to rely on a combination of the first two for a TEOTWAWKI situation.
Okay, so what happens if you don’t loose your stuff but are taken hostage instead? What if the bad guys see someone out foraging that they figure is from a retreat and they take him hostage and follow their tracks back to the retreat? Should they go through torture to avoid giving a signal? Should they risk being a friendly fire casualty by approaching without a signal? This is where “duress” signals come into play. This makes it look like you are authenticating, but in actuality you are signaling that you are under duress and it gives your team warning to tactically deploy with discretion to give you and your new companions a proper greeting. Duress signals should be added as part of the SOP for replies from the compound as well. If you are overrun or surprised through treachery while part of your party is out, you want the ability to appear to be signaling them all clear in the eyes of the adversary while in reality sending the signal that all is not well. – G.V.