Using simple text cyphers in your games

Introduction

This article will present motivations, creation, and usage of simple text cyphers for creating written messages, markers, and missives. These methods can be pictorial chalk marks on cavern walls, missives between troops/henchman, spy networks, or even to represent written language. They can be used to provide challenges to the player's directly or in conjunction with their character's skill sets and linguistic knowledge. This article begins with a focus on two methods, substitution and Morse Code, and then concludes with ideas for incorporating encoded messages can be integrated into your game or campaign.

Cyphers

Simple substitution cyphers

Perhaps the simplest form of cypher is substitution, where a singular letter is substituted with another. Shifting - Simply, this method shifts the letters/characters of the message by a constant index like 3. If you think of the latin based English alphabet of a-z as a loop, a becomes d, b becomes e, until z becomes c and completes the loop. With 26 characters in this alphabet, the index range is from 2 - 25 and can be negative where with an index of -3 where a becomes x, etc.

Example (index of 5): Move your troops to take the right flank
applying the cypher method results in: rtaj dtzw ywttux yt yfpj ymj wnlmy kqfsp

You can simply reverse the alphabet, where a becomes z, z becomes a, etc.

Example (reversed): Move your troops to take the right flank
applying the cypher method results in: nlev blfi gillkh gl gzpv gsv irtsg uozmp

In the above examples, the word length remains consistent with the original message. To obfuscate further, consider adding a space as its own character in the cypher, resulting in a 27 character circle.

Example (index of 7, space inclusive): Move your troops to take the right flank
applying the cypher method results in: tvblgevayg yvvwzg vg hrlg ogypno mshur

Morse code based cyphers

A different set of substitution cyphers can be created based on Morse code. Morse code is a method that encodes each letter of the alphabet into a series of "." and "-" where letters (and numbers) do not have a uniform length. There are several refinements and extensions to include punctuation, but this article will limit itself to the International (ITU) standard. You can choose your own pairings of substitution glyphs including Cyrillic, Greek, Unicode symbols to create hundreds of different variants, enough to keep your players challenged and a message (if used to represent a language) hidden from the characters until they can locate assistance with the translation/decryption.

Be creative, you can use the Morse Code with any phonics, for example a "." can be "uh" and a "-" can "hu." Make a recording of the message and play it back to represent a conversation being overheard.

Example: Move your troops to take the right flank
applying the cypher method results in: -- --- ...- . -.-- --- ..- .-. - .-. --- --- .--. ... - --- - .- -.- . - .... . .-. .. --. .... - ..-. .-.. .- -. -.-
Substituting a "/" for "." and a "\" for a "-" Example : Move your troops to take the right flank
applying the cypher method results in: \\ \\\ ///\ / \/\\ \\\ //\ /\/ \ /\/ \\\ \\\ /\\/ /// \ \\\ \ /\ \/\ / \ //// / /\/ // \\/ //// \ //\/ /\// /\ \/ \/\
Substituting a "<" for "." and a ">" for a "-" Example (morse code): Move your troops to take the right flank
>> >>> <<<> < ><>> >>> <<> <>< > <>< >>> >>> <>>< <<< > >>> > <> ><> < > <<<< < <>< << >>< <<<< > <<>< <><< <> >< ><>

Complex (combined) cyphers

The Morse Code method above uses spaces (or in the case of audible representation, a pause) and suffers from singular character delineation. To further mask the original message, you can combine the Morse Code with a substitution ring (see above).

Bacon's Cypher (variant)

Another plain text cypher is Bacon's cypher which is not vulnerable to the same singular character delineation mentioned previously. Bacon's Cypher uses five characters/glyphs to represent the alphabet. The original Bacon cypher used a single combination to represent both i and j, as well as a single combination for u and v. A variant exists that distinguishes these and is used here.

Example: Move your troops to take the right flank
applying the cypher method results in: abbaaabbbabababaabaa bbaaaabbbaubaaab baabbbaaababbbaabbbaabbbbbaaba baabbabbba baabbaaaaaababaaabaa baabbaabbbaabaa baaababaaaaabbaaabbbbaabb aabablaaaaaabbabababa
Each of the above methods have vulnerabilities (word and character distinction) but can still help a game master present a variety of messages that the characters have to get creative to decode.

Using in your game

There are many uses for encoded text in your games, from cave markings, secret missives, and languages, let your imagination and knowledge of your gaming group guide you in your usage of them. Some players are not puzzle solvers and may not enjoy or even get frustrated when faced with such a challenge. Don't let this be a burden to them. Whether it is used as a language or a technique to hide a message, decoding or translation should not be out of the characters reach.  Used as a language, some characters may possess knowledge of the language and are able to translate, or translation services might be available for hire, thus you can just easily hand them the translation. Intelligence based skill checks (or similar depending on your game system) can be used to solve/translate them, but clock time might be important. A partial decoding of a missive might be found along with the original that provides enough clues to solve it.
The actual message content may not be important, but its existence reveals that forces are at work that rely on such methods of communication.  Seeking services to translate/decode a message may lead the characters to location or an NPC that is vital to the continuing story. Now, don't run out and create every conceivable language using these methods. That would be a lot of work and unlikely to be fully utilized. However, as you do define a language/use, take note of it so you can be consistent in your games. Make it fun!

Gorcik paces outside his command tent awaiting the arrival of the days overdue courier.  A horse's whinny cuts through his musing and as he looks up, he sees a rider approach the camp.  He doesn't recognize the couriers face, but the uniform and marking appear true.  As the rider dismounts and approaches Gorcik, the blood and bruising on the courier become apparent.  Gorcik glances over at the horse and notes that he has been ridden hard as it is led away by keepers to cool and care for the horse. The courier hands a written message to Gorcik who dismisses the courier to seek medical attention and the courier moves off.  Gorcik calls out his lieutenants to his side.  Gorcik thinks I'll just translate this on the fly.  This courier appears stressed and don't want to waste any time. As his lieutenants gather round their leader, Gorcik breaks the seal on the missive.  It is short and contains the following:  

> >>> >>> <><< <> > <

Gorcik recognizes the code quickly, but is slightly confused by the use of it, since it had been retired and replaced by a more sophisticated one.  Rotating and changing codes during a campaign such as this is not new, so Gorcik doesn't give it another thought until he completes the decoding.  At that moment, Gorcik looks up to see that he and his lieutenants are consumed in a volley of arrows.  His eyes widen as he hears the thud of an arrow find its mark and his last thoughts are of the message contents...

too late