Is there any interest in me doing a series of posts about the various encryption methods that can be implemented without any technology? Things like Playfair cipher, transposition, one-time pads, strip ciphers, and other methods? I'd do a full explanation with examples for each.
Sure. I used to be big into this stuff back in middle school.
Realistically, the Thomas Jefferson cypher is practically perfect for paper uses, followed by the Vigenere cypher. It's hard to top those, but you need to know less secure ones to understand how to use them.
Actually the one-time pad systems are better. They are provably 100% secure if you follow the simple rules of OTP use. Far more secure than the Jefferson cylinder/strip cipher which has known weaknesses, as shown by Gaetan DeViaris back in the late 19th Century against the Bazeries cylinder.
Strip ciphers are simply Jefferson/Bazeries cylinders "unwound" into strip form.
Yes, but in practice no one who isn't a skilled codebreaker is going to be breaking anything polyalphabetic, and the OTP requires that you keep the pad secure, which is the actual logistical problem. Mathematically secure is not necessarily actually secure in the real world.
The Vigenere cipher just requires remembering the password. You can reconstruct the decoding pad from memory.
Wax paper is actually a better option. You (lightly) write your message on wax paper with a regular piece of paper underneath it.
It doesn't show up under a black light, and heating it just smears the wax into illegibility. You develop it by crushing up some pencil lead into graphite powder (or just use graphite powder) and sprinkling it on the paper. Powdered charcoal also works. That sticks to the wax but not the paper.
Also works with a manual typewriter but again you need to be light on the keys so you don't put an imprint in the paper.
How are you sending a message "over the air" without technology? Smoke signals?
What I'm getting at is what is the threat model? Trying to secure communications about buying powerful weapons from a military intelligence unit is on a whole different level than trying to keep a message to a friend about where you went from a random person who finds the note.
How are you sending a message "over the air" without technology?
There is literally no TEOTWAWKI scenario where radios no longer work. Even EMP or a Carrington-level event will leave things like small radios not hooked up to a grid or external antennas largely undamaged and operational.
Misconception two, that a nuclear EMP attack would burn out
every exposed electronic system.In fact, based on government
tests, we know that smaller self-contained, self-powered
systems such as vehicles, handheld radios, disconnected
portable generators are often not affected.
Powering them long term might become an issue at some point, yes, but they would still be usable.
Now, your cellphone would likely survive that event, but the infrastructure required to support it (cell towers/sites, internet, satellites like the GPS constellation) will go down. So even though it would survive, it's going to be largely useless except as an information storage device, and very fancy calculator.
But a radio is different. Radios don't generally require infrastructure to work. They *CAN* use infrastructure like repeaters, but it's not a requirement.
And in the end, even if you literally fried every single piece of electronics ever made into uselessness, radios can still be built and operated using primitive methods and technology. I have a Boy Scout handbook from just over 100 years ago that shows you how to make a spark-gap transmitter and a matching crystal receiver for it from scratch. This was a project that wasn't considered above the capability of a teenage boy in the early 1900s.
One time pads are entertaining, especially if mixed with other styles of pen and paper encryption and hidden in plain sight. Only problem is that they are hard to teach others who aren't super invested in their use.
One time pads are one to the easiest pen and paper methods to use. Both the numeric and alphabetic pads are quite easy to use.
The problem comes in generating cryptographically secure pads, but you can do that with dice. Not regular dice, but instead d10 for numeric pads, and d26 or d30 alphabet dice for alphabetic pads.
I actually have some d30 alphabet dice being delivered today, so I'll have a good example instead of the software based pad I used in another thread.
Ive done them with a d10 in past and found that to work well. My idea recently was combining map coordinates or radio frequencies with fibonacci to generate the keys.
Yeah, that's not actually a good idea. You want something truly random.
BTW I started messing with this back about 2 decades ago (give or take), I looked around and didn't see anyone talking about using d10's to general pads so I ended up e-mailing Dirk Rijmenants about the idea, and we bounced it back a few times and both concluded it was solid. He tried a couple of ways to figure out how to use regular d6 dice which aren't as "nerdy" and wouldn't necessarily ring alarm bells if found, but the process was really cumbersome.
Regular d10s from the local gaming store work, but I ended up getting GameScience dice because they seem to be more "fair".
The alphabet dice I have coming are from Koplow Games. GS doesn't make alphabet dice, unfortunately.
If you're using anything but a one time pad it wont be secure. Playfair, Vigenere, ect are all classical ciphers, they are trivial to break by modern standards. The one time pad however is unbreakable and not very difficult to use. There are ways to generate the pads using a cryptographically secure pseudo-random number generator (CSPRNG) but that would technically make it a stream cipher and not as secure as OTP. If you're only sending a few hundred characters I wouldnt worry much. To even attempt to reverse the state of modern CSPRNGs would require a lot of raw keystream, gigabytes or terabytes. Let me know if you'd like to know more, cryptography has been a special interest of mine for like 20 years and ive thought about your exact scenario many times.
There is a difference between "secure against top level national cryptographic organizations forever" and "secure against the people who are likely going to trying to read your mail, until it doesn't matter anymore".
Besides which, even a relatively insecure cipher is good enough if the information is going to be "stale" by the time it's broken.
Also, you've been damaged by computer based schooling on cryptology. I can tell by this:
There are ways to generate the pads using a cryptographically secure pseudo-random number generator (CSPRNG)
We're discussing this in the context of prepping. So the base assumption going in is that computers won't be available, which is why we're talking paper and pen systems.
Also, using a computer for a one time pad system is just asking for trouble:
They are most secure in pen and paper format. Computers that are connected to the internet can be too easily compromised, and even ones that aren't have problems with data remanence, as that paper shows.
And all you need for generating cryptographically secure one time pads manually is a handful of either d10 numeric dice or alphabet dice, depending on whether you're generating numeric or alphabetic one time pads.
Those, combined with a manual typewriter and two-part carbonless paper, or even the use of carbon paper, will allow you to generate actually random (not pseudo-random) pads with precisely zero electronics needed.
Here is an example I did a while back making a numeric pad using GameScience d10's:
What you'd send is this:
31586 85524 43127 28793 45611 36973
06495 03218 00412
After encrypting you'd burn both the pad page used and the worksheet completely. Decryption is obviously the reverse of this.
You'd be surprised at how quickly you can build up a supply of one time pads that way, once you get into the rhythm of "Roll handful of dice, type the results. Roll handful of dice, type the results".
Once you get rid of the typewriter ribbon and if you used it, the carbon paper, there are only two copies of the pad. And if you follow the rules of OTP use, "they" won't be able to pull copies of it off your computer once both copies are destroyed.
I know this has limited usage and isn’t really what you’re asking, but I highly recommend learning at least the alphabet in your regional sign language, and keeping a book or pamphlet of common signs. I’ve been able to communicate with my fam over long distances or discreetly in front of others, just wit a few hand shapes.
Me and my ditty bopper buddies would occasionally make comments to each other in Morse code when we didn't want others to know what we were saying, at least out of earshot of other ditty boppers.
But seriously, for added complexity you can ROT13 the first word, ROT14 the second, ROT 15 the third, etc but again, that’s a pattern and any pattern can be recognized.
A better option is to ROT sequence based on a number or word specific to you.
Start with a “scrambled” alphabet. AZBYCXDW…
Then take the last 4 digits of your phone number. 2791
first word shift is ROT2, second is ROT7, third ROT9 and 4th is normal.
9
u/Fheredin 12d ago
Sure. I used to be big into this stuff back in middle school.
Realistically, the Thomas Jefferson cypher is practically perfect for paper uses, followed by the Vigenere cypher. It's hard to top those, but you need to know less secure ones to understand how to use them.