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Templarkommando
2011-11-04, 04:52 AM
It occurs to me that there is some decent promise for an adventurer looking for the keyword of a substitution cipher. Here's how a cipher works:

Step 1: Pick a keyword. There are lots of arbitrary ways to pick a keyword. You can leave yourself a hint by picking the first word on a page of your favorite book. That way you can write the page number and whoever receives the message can figure out the keyword. (Our word for now will be chicken)

Step 2: Write out your alphabet with the keyword at the beginning and place it over the actual alphabet. Do not repeat the extra letters. So our actual keyword is closer to chien.

C H I E N A B D F G J K L M O P Q R S T U V W X Y Z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

An alternative option when you're keywords letters tend toward the beginning of the alphabet is to flip the alphabet around backwards so:

C H I E N Z Y X W V U T S R Q P O M L K J G F D B A
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Step 3: write out your message.

"Encryption is cool" becomes "Nsimbpkwqr wl iqqt"

Step 4 in order to prevent those spying on your message from knowing what you're writing about pair up letters like so:

NS IM MP KW QR WL IG GT

Bascially, it will be up to your junior adventure space cadets to figure out what the heck en cr yp ti on is co ol means.

Heres where this might get shot down by a single die roll. According to the Rules Compendium, you can create a cipher over the course of a week with the decipher script skill, and anyone trying to figure it out in a day, but if they fail it then takes a week.

In the meantime, a pretty cool series of quests could be put together to recover the key word for the cipher, the message, and then chasing after a quest based on the information gleaned from decrypting the message.

Happy Hunting. I would be interested to see other ways of writing secret messages.

DoctorGlock
2011-11-04, 05:38 AM
Just make sure your encryption key isn't the product of 2 prime numbers, that's exactly the sort of thing the Germans will look for.

Firest Kathon
2011-11-04, 05:49 AM
I'm not exactly sure what the point of your post is. If you are complaining that the whole decryption can be done by a single die roll, instead of taking the quest, have the author of the message use a one-time pad (http://en.wikipedia.org/wiki/One-time_pad), which cannot be broken without the key (in theory), and rule that it cannot be decyphered without a key and therefor the decipher script skill does not apply here.

Templarkommando
2011-11-04, 12:36 PM
Mostly, the point of the post was to give a friendly idea for adventure from one DM to another, or perhaps from one player to another. I do like the way of getting around the use of the decipher with a one-time pad though. I had actually been trying to remember what those things were called.

CarpeGuitarrem
2011-11-04, 01:39 PM
If you want something cool and simple-to-understand, you could also use a grille scrambler (http://en.wikipedia.org/wiki/Grille_(cryptography)).

Vire
2011-11-04, 02:07 PM
also make sure you don't leave the K from chicken out of your cipher, or you'll have a useless code that nobody will figure out. :smalltongue:

Beleriphon
2011-11-04, 03:21 PM
{table]D|I|C|T|O|N|A|R|Y|B|D|E|F|G|H|J|K|L|M|P|Q|R|S|U|V| W|X|Y|Z
A|B|C|D|E|F|G|H|I|J|K|L|M|N|O|P|Q|R|S|T|U|V|W|X|Y| Z
[/table]

Enjoy the table, and substitution cipher.

GungHo
2011-11-04, 04:00 PM
You should also consider your audience when you come up with these sorts of things. By this I mean, you could spend your time writing a clever crossword cipher that might be enjoyed by someone who reads Games magazine or is a hard-core spy fiction afficionado, but it's a waste of time if you're dealing with some folks who probably couldn't get ROT13, who would be completely confounded by a Dvorak keyboard, or who think Dan Brown is the cleverest man on earth. I do not mean to sound dismissive in the slightest, but unless your group is in Langely, VA, you probably don't need something that's going to withstand frequency analysis.

I've done some very elaborate things before and watched it just go nowhere because I game with the cast of King of the Hill.

Beleriphon
2011-11-04, 04:02 PM
I do not mean to sound dismissive in the slightest, but unless your group is in Langely, VA, you probably don't need something that's going to withstand frequency analysis.

Or, you know think The Cryptinomicon is the best novel ever.

CrazedPachyderm
2011-11-04, 04:19 PM
Ha, in the game I run, 4/5 of us are working on PhDs in math. One time the characters found a secret message, encrypted with a simple substitution cipher. The non-mathy player snatched it up and went right to work at it. With an Intelligence check, I saved her some time by providing a frequency count of the symbols, and I had a few more clues prepared if they were needed. It didn't take long for her to crack it, but it kept her busy and amused while the other characters were in combat.

DeadManSleeping
2011-11-04, 05:10 PM
Any message shorter than, say, 50 characters, is going to be nearly undecipherable as long as you use a decently complicated cipher system (a Playfair (http://en.wikipedia.org/wiki/Playfair_cipher) should do fine for that length). More likely, though, for adventurey stuff, you'll want to use a transposition cipher, which is time-consuming to piece together. For transposition ciphers, you can hide clues in otherwise obvious places, because the key to a transposition cipher is usually very, very short and non-obvious without context!Example (http://en.wikipedia.org/wiki/Transposition_cipher#Columnar_transposition): 500-character message. Break it up into 50 rows of 10, then write out the columns (so now you have 10 rows of 50-character-long jibberish). Then re-order the "columns". The "key" is 10 digits (showing the proper order of the 50-character sections). You don't even need to specify the grid size, since the key makes it obvious that it's 10 columns. Step 2: Make some adventure that would necessitate recovering the numbers of the key in order.

Just an idea off the side of my head. I'm sure there's better stuff to do with cryptography for RPGs. That's all just the first thing I thought of.

Templarkommando
2011-11-04, 07:47 PM
also make sure you don't leave the K from chicken out of your cipher, or you'll have a useless code that nobody will figure out. :smalltongue:

Yeah, a couple of hours after I wrote that, I got to lookin' at that and was like.... oh crap...:smallbiggrin:

Gralamin
2011-11-04, 08:44 PM
Cryptology is a bad thing to bring up with groups that contain programmers, you end up with things like this:


baab 64d6 9951 782a f98e c432 c6b9 17b4
16b2 4d60 aec3 ba49 6d86 7c6a aeb6 9894
e6ea 4f99 efe9 a02c 7601 0754 65da 913d
519d 79f6 0a73 031b 939d 352b 2119 00df
34c3 f213 992b 1d6c d13a 9413 ba7a 2075
d97e 15e5 cbda 704d d19f 62b1 e141 2284
2a68 f61c 5f44 c871 e8d9 cc1d c779 9bef
6dc1 d972 caad de7c a9f4 dfd1 7367 1a58
c673 01b7 4242 f45b ac8f f59d f549 2bdc
1dff ce0f eac6 4036 3ff4 ae4a b4b1 d800
45e5 f9c8 2b86 c175 fd45 8845 f829 9500
8633 6388 3405 b6f0 6ba0 906b 9dc7 75a9
59f6 6110 92e8 943a a1c9 9545 a14d 91fa
0959 6336 058d 5c83 c6bc 8c44 c9e2 e5c4
e5d1 c1dc b76a ac34 e298 cca2 5c7e e278
e0c2 b9a2 b38f e014 ba98 99a3 0ae9 39bc

Translates to: "Meet me at the bar". Don't try breaking it yourself, it will take much too long.


The problem with a lot of cryptology though is most fantasy games have a comprehend languages... Which invalidates cryptology since it is very easy to argue that any piece of encrypted text is the same as being in a different language. In sci-fi it is super useful, especially Hard sci-fi.

Eakin
2011-11-04, 08:56 PM
The problem with a lot of cryptology though is most fantasy games have a comprehend languages... Which invalidates cryptology since it is very easy to argue that any piece of encrypted text is the same as being in a different language. In sci-fi it is super useful, especially Hard sci-fi.

Encrypted text is NOTHING like being in another language, unless the language YOU speak changes grammatical rules and vocabulary every sentence. Assuming you do encryption even vaguely right (http://en.wikipedia.org/wiki/Polyalphabetic_substitution)

Templarkommando
2011-11-04, 09:19 PM
Cryptology is a bad thing to bring up with groups that contain programmers, you end up with things like this:


baab 64d6 9951 782a f98e c432 c6b9 17b4
16b2 4d60 aec3 ba49 6d86 7c6a aeb6 9894
e6ea 4f99 efe9 a02c 7601 0754 65da 913d
519d 79f6 0a73 031b 939d 352b 2119 00df
34c3 f213 992b 1d6c d13a 9413 ba7a 2075
d97e 15e5 cbda 704d d19f 62b1 e141 2284
2a68 f61c 5f44 c871 e8d9 cc1d c779 9bef
6dc1 d972 caad de7c a9f4 dfd1 7367 1a58
c673 01b7 4242 f45b ac8f f59d f549 2bdc
1dff ce0f eac6 4036 3ff4 ae4a b4b1 d800
45e5 f9c8 2b86 c175 fd45 8845 f829 9500
8633 6388 3405 b6f0 6ba0 906b 9dc7 75a9
59f6 6110 92e8 943a a1c9 9545 a14d 91fa
0959 6336 058d 5c83 c6bc 8c44 c9e2 e5c4
e5d1 c1dc b76a ac34 e298 cca2 5c7e e278
e0c2 b9a2 b38f e014 ba98 99a3 0ae9 39bc

Translates to: "Meet me at the bar". Don't try breaking it yourself, it will take much too long.


The problem with a lot of cryptology though is most fantasy games have a comprehend languages... Which invalidates cryptology since it is very easy to argue that any piece of encrypted text is the same as being in a different language. In sci-fi it is super useful, especially Hard sci-fi.

I would say encryption is just a flavoring for a campaign world. It's like salt. A little salt makes your meal taste better and to a degree can provide a bit of necessary nutrition, but if you just dump a pound of salt on everything, then your meal is gonna suck. It's something that an aspiring DM can use to season a campaign, it's not an end-all-be-all adventure builder, it's just an option in your cabinet of literary spices.

DeadManSleeping
2011-11-04, 09:46 PM
Encrypted text is NOTHING like being in another language, unless the language YOU speak changes grammatical rules and vocabulary every sentence. Assuming you do encryption even vaguely right (http://en.wikipedia.org/wiki/Polyalphabetic_substitution)

Ooh, and a Vigenere can even have a keyword! Crap, how did I not think of that first? Man, it's been too long.

Eakin
2011-11-04, 10:17 PM
Ooh, and a Vigenere can even have a keyword! Crap, how did I not think of that first? Man, it's been too long.

Meh, if I hadn't had an exam on crypto three weeks ago I probably would have forgotten that too. But yes, any simple "key" you can send your PCs after so they can decode the message is a great hook. With a Vigenere you can even have them do it themselves if they're into that.

You could also use a scytale (http://en.wikipedia.org/wiki/Scytale)