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Tactical Corner / Re: Sending Encrypted Messages in Morse Code.
« Last post by lpwaterhouse on August 03, 2018, 05:04:23 AM »

I just discovered the youtube channel and the OTP video drew me here. I'm a bit of a Cryptology nerd and want to chime in on some of the commonly glossed-over details, misconceptions, etc. that are nonetheless surprisingly vital in keeping your communication secret, especially regarding the perfect secrecy of OTPs (which is _far_ more impractical than most people assume). Gil does mention all of the problems, but I think they bear pointing out even more explicitly:

While it is true that a properly generated One-time Pad is information-theoretically perfectly secure, the devil is in the details of that "properly generated". The perfect security ONLY applies when a source of actual, physical, randomness is used, with proper precautions to eliminate biases, etc. The problem is that it is very hard to be sure your source _is_ actually random (Generally nuclear decay, Thermal (Johnson-Nyquist) noise, Avalanche Diodes or the last bit of a microsecond time difference between keystrokes are usually considered "good, as far as we know"). If instead you use any kind of Pseudo-random number generator [PRNG] (e.g. /dev/random, rand(), that formilab site, etc.) then the security guarantees drop from "perfect" to that of an ordinary StreamCipher (in fact "Adding/XORing with an algorithmically generated Key-Stream" is a definition of StreamCipher), subject to the quality of the PRNG, but always lower than "perfect". Some such PRNGs are "cryptographically secure" [CPRNG], meaning that while they aren't "perfect" we _currently_ know no way of breaking them. The majority of PRNGs however are utterly unsuitable for cryptographic purposes, they were designed for statistical properties instead.

So, if you truly want to approach the perfect security of the OTP you MUST use a hardware or "true" RNG [TRNG], and pay attention to whether the cryptographic community considers that particular design "good, as far as we know". Some possible options are or

If you have no access to a TRNG (or you realize that "perfect" is the enemy of "good enough") then you are probably better off using an established cryptographic algorithm, because they a) are likely equal or better than anything you can assemble with a PRNG, even if cryptographically secure, and b) don't share the major drawback of OTPs (or rather: pre-shared key-streams), namely having to _securely_ share a "pad" with the recipient ahead of time, that is at least as long as all messages you ever intend to exchange concatenated (The only advantage of this over communicating securely directly is that it can be shared ahead of time, when circumstances can make it easier, e.g. face to face). There is a good reason even governments/spy agencies don't often use OTPs, exchanging and storing that much highly sensitive "pad" is truly difficult (And then you still have to be extremely careful in using it correctly, or you can easily make non-obvious mistakes that render you encryption surprisingly weak, read up on the "Venona project" for when that happend to the Soviet Union. For example: NEVER EVER repeat the pad! One repetition IS enough to break it, relatively easily even!)

So, what if you only need "good enough"? Meaning something that, according to current research (publicly available only, of course...) would either take longer than the expected life-time of the universe to break, or something that only needs to be secure against non-government adversaries, like your neighbors?

Your best bet is well-established and internationally vetted systems, preferably using public-key algorithms (So you don't even have to exchange the, relatively short, compared to an OTP, key securely), for example RSA with AES.

But those of course require computers and access to cryptographic software (something that many governments consider restricting from time to time...), so you want something that can either be programmed from memory or works without any computer at all, "in the field". I suggest having a look at these two options in particular:

    - CipherSaber-2 ( using RC-4, an easily memorizable algorithm that most programmers can code in a few minutes, with practice. RC-4 itself is considered insecure against determined and knowledgable adversaries, though the modification in CipherSaber-_2_ is likely to alleviate that somewhat. In a SHTF (as opposed to an Orwellian) scenario I wouldn't hesitate to use it.

    - Solitaire (, also known as "Pontifex" (in the "Cryptonomicon" Gil mentioned) working without a computer, using an inconspicuous deck of playing cards. Not much research seems to have gone into the security of Solitaire (though its designer is a respected cryptographer), but its construction suggests it may be vulnerable to the same kind of attacks as RC-4. Still: Certainly good enough against your neighbors. Try it (the password is "GL", which is too short for real use, and I'm not using the optional keying step of setting the Jokers): "LEZVJ RUQLK BCTED"

And last, but not least: In case you want to learn some cryptanalysis and break some ciphers (including a few used by the US army in WW2), have a look at It can be quite eye-opening...

Antennas / Successful Wire Antennas.
« Last post by gil on August 03, 2018, 03:10:37 AM »

Here is a great PDF file I found on wire antennas. They forgot the W3EDP, but otherwise, it is quite informative. The file is attached to this message.

DMR Radio / Re: New Board: DMR Radio on Radio Preppers.
« Last post by Quietguy on August 03, 2018, 02:19:08 AM »
Is it real radio? Well, only between the repeater and your handheld, otherwise, no.

But it also makes simplex connections, so it is just as much Real Radio as any 2m/70cm HT or mobile, it just has more capabilities.  It works radio to repeater to radio for local coverage just like analog radios, no Internet needed.

Also, if you have Internet capability at home you don't have to be near a repeater for distant contacts.  You can have your own imitation repeater in the comfort of your living room by setting up a personal hot spot.  There are several, some based on the Raspberry Pi and others more plug and play.  The SharkRF Open Spot is a plug and play hotspot that allows linking to the Brandmeister network for worldwide contacts.  So you can use your HT to talk across town to a friend simplex or you can use a hot spot with Internet to talk anywhere.

Cheap.  Dual band (2m/70cm) DMR plus analog FM for $170 shipped (in the US), complete with built-in GPS so two units linked simplex know how far apart they are.  Not bad for search and rescue efforts.

Net Activity / Re: Radio Vacation
« Last post by dylan on July 31, 2018, 07:49:27 PM »
Well shucks. Called CQ for about an hour around 14.060, +/- a little and no replies. Otherwise perfect day in the woods. The EFHW tunes up with an SWR around 1.3:1. The antenna is pointing due south and elevated 10-15' above the ground.
DMR Radio / New Board: DMR Radio on Radio Preppers.
« Last post by gil on July 31, 2018, 09:48:00 AM »

We have a new board! I need to say that for prepping purposes DMR might and probably should not be very high on your priority list. We assume that during SHTF there would be no grid power, let alone any Internet service. That said, it does allow encryption, which is however illegal in normal times...

DMR has taken the amateur bands by storm, and for good reasons. It is an open source mode. Everyone can implement it into their radios. Although it was designed for commercial radio use, it does work well for amateurs, well enough anyway. There is a learning curve, but honestly, once you learn the vocabulary, it is pretty simple. What's the advantage? It is worldwide... You can talk to anyone anywhere there is a repeater connected to the Internet. Is it real radio? Well, only between the repeater and your handheld, otherwise, no. It's still better than network radio, which isn't radio at all and should be called something else.

In any case, it is hard to ignore DMR today. My take on it is that if you buy an analog radio, you might as well get a DMR/analog radio, since they all do both. So I decided to start this new board. Ya'll have fun now and keep it civil  ;)

DMR Radio / Worldwide DMR Users File for Retevis RT3S, MD-380, etc.
« Last post by gil on July 31, 2018, 09:37:56 AM »
First post in this new category!

Since I am using the Retevis RT3S dual band DMR radio, I wanted to import all worldwide users into its database. I found the following site:

Click on DMR User ID List, space separated fields (ID call name)

The format is not the same as what is used by the RT3S, though it is CSV, but the columns are different. I wrote a small Python program to convert it. The resulting file, which will be attached to this post, does import correctly into the Retevis software, and I suspect will work with other Retevis.TYT radios. I have not tried to insert my new file into the radio, but I don't expect any trouble. Stay tuned for an update and video!

I will update this file every few months...

Net Activity / Re: Radio Vacation
« Last post by dylan on July 30, 2018, 11:26:15 AM »
I suspect that you have "heard" this radio before, I bought it from Ray. I'm still trying to figure out the best way to attach the EFHW to the QRPGuys EFHW tuner so that the antenna wire isn't pulled out from under the wing nut.
Net Activity / Re: Radio Vacation
« Last post by gil on July 30, 2018, 08:24:37 AM »
So that would be 22:00 for me here in France. Maybe I'll listen on my MTR3b :)
Keep us all updated!
Net Activity / Radio Vacation
« Last post by dylan on July 29, 2018, 05:56:38 PM »
Hi folks. Thanks for sharing so many great stories, reviews, and ideas.

I am planning to be on 20 and 40 meters CW this week, operating with an MTR5b and EFHW antenna from the north coast of California. I'll likely be hanging out near the middle of the CW portion of the bands, between 1-3pm pacific standard time. I think that is a -7 GMT offset. I'll send a photo and review of my temporary station once I get it setup.

Antennas / Re: The 49:1 Half-Wave End-Fed Transformer Campain is ON!
« Last post by caulktel on July 28, 2018, 12:43:44 PM »

I don't know if you will be able to read this thread or not, but it's all about EFHW and 49:1 transformers and the like. Some of the people were shouting at each other, but still some good information.,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,23807137

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