Although many think of pen and paper ciphers (encryption using a writing utility and paper) are obsolete, I still find uses for them. I like using the ciphers, and I would like to find more. In my list that I already use, I have: SECOM PPC-x RSA (Pen and Paper style) Does anyone have any suggestions of any strong pen and paper ciphers? They are greatly appreciated. Thanks, SFI
Why not make your own? Old ciphers used a simple letter substitution scheme. They were potentially vulnerable to decoding by checking the frequency of use for each character, provided the decoder had access to enough encoded material. That could be made much more difficult by using more than one character for the more common letters, like 3 different characters for "E" and "T", 2 for "R" and "S", etc. Use extra characters that aren't part of the data to make it harder, such as every other character is meaningless. Break everything into 5 character groups. Have additional symbols for spaces, periods, etc. I used to play with ciphers when I was young. It was fun but I can't honestly say I had a use for it.
How about the classic One Time pad? One-time pad An old school OTP (One Time Pad) is perfect encryption as long as: 1) the pads are truly random. 2) You never reuse the pads. 3) The pads aren't intercepted or compromised.
So, following noone_particular's advice, I made my own cipher, I'm still testing it, so I won't post it yet. As soon as I confirm it is secure (to a reasonable degree) I may post it. With the one-time pad, I don't like using that because you need a lot of random data, and with such large loads of data, it is hard to give it to the other party. Not only that, but the keys must be truly random. I know that a few online sources offer this, but I might need a lot of data. Thank you very much for your contributions.
OTP's are the best and most secure to use. Why else would intelligence agencies around the world still use this for operatives "in the field" and the higer diplomatic community. And using OTP's is simpler to use then all the other ciphers that crossed this topic so far.
check out Neal Stephensons Cryptonomicon. In the book (described in more detail in the appendix) he describes a cipher using a deck of cards. He seems to feel it was pretty strong encryption. He used in a prisoner situation. So if the guards come to check, you can simply drop the deck on the floor and no way to decode the message. Sorry don't have the book handy to check.
If it helps, the cryptosystem in Cryptonomicon, "Pontifex," is actually Bruce Schneier's "Solitaire." He [Bruce] gives a breakdown on how it works, here. Not only is it fun to play with -- it has some interesting security properties too.
I thought Solitaire was developed by Bruce for the book, not the other way around. I have looked into that, but I wanted something that only required pen and paper, is easy to memorize and will have a easy to remember key. I have tried the Solitaire method, and is very fun to use.
It was; that's what I intended to get across. Bruce Schneier dubbed his design "Solitaire," but it's known as "Pontifex" in the book. I'm actually reading Cryptonomicon right now -- it's continuing to lure me in, so that's a plus!
I have to say, I'm finding it really slow to start... I find myself skimming over the excruciatingly laborious detail with which the author describes everything. It could easily run to 300 pages instead of its present 900+ if he wrote lucidly. I'm not too fond of how the book encompasses several different storylines, although I'm sure they must converge at some point. What I am enjoying is the Lawrence Waterhouse/ Bletchley storyline.
