[Basic] Skill of the week: Cryptography

[johndallman]

Cryptography is the IQ/H TL-dependent skill of making and breaking encryption systems - usually codes and ciphers. It isn't required for simply using an encryption system, which comes under the skill used to operate a communications system, such as Electronics Operation (Communications), probably as a familiarity. The skill is boosted by Mathematical Ability, and the only default is Mathematics (Cryptology)-5, which seems a bit harsh: -3 would feel more reasonable, given that this is the major application of that Mathematics specialisation. The skill covers all the normal techniques of its TL, from the simplest to the most up-to-date, and an optional specialisation in either creating or breaking codes is common.

Creating a new encryption is done with a skill roll, and taking extra time is common. There's a special rule using the speed/range table for getting a skill bonus for taking extra time (use days in place of yards, read off the bonus) which could usefully be applied to other creative skills. Breaking encryption is done with a quick contest of Cryptography, with a base time of one day, but the code-maker always uses his original roll. The code-breaker ought to be allowed to take extra time, and using the speed/range table rule might well be reasonable.

Both sides benefit from computers, by up to +4. A code-breaker gets +5 if he has a translation of some or all of his sample of the code, and -5 if his sample is very small. Higher-TL ideas can make breaking some low-TL cryptography much easier; there's a case for a higher-TL code-breaker to get bonuses instead of penalties for the TL difference, if he has information about the lower TL's usual encryptions, and tools of his own TL.

There is a special case default for Cryptography to IQ-5, for making trivial codes, which won't stand up to anyone with the skill for long, and for breaking trivial codes, but not professionally designed ones. This rule seems OK from personal experience, having broken a copy-protection scheme produced by a former employer, which the creator thought was sound, in well under a day. I might be able to claim a Dabbler perk in Cryptography but I certainly don't have a point in the skill.

High-Tech has more detailed rules, which say that the Basic Set rules are for manually devised encryption, not the modern kinds based on rotors or hard mathematical problems, and give new timescales and equipment costs. Ultra-Tech has less specific rules for future TLs. Bio-Tech offers DNA computing for cryptography. Action 2: Exploits has action-movie rules for modern-day code-breaking. Spaceships 5 covers reading alien civilizations' digital communication protocols. Supers has the Coded Thoughts technique of Mind Block, which allows a sufficiently powerful mind to think in code, and thus resist mind-reading, and Thaumatology considers magical books written in codes.

Cryptography appears on templates or lenses in Action, Fantasy, Horror, Madness Dossier, Infinite Worlds, Locations: Metro of Madness, Worminghall, Martial Arts, FCCT, Monster Hunters, Mysteries, Psis, Space, Tales of the Solar Patrol, Thaumatology: Magical Styles, Ritual Path Magic, and Urban Magics. PU3: Talents and PU7: Wildcard skills both have examples that include Cryptography.

I don't think I've ever seen Cryptography used during a game session. Our hackers have had players who weren't into the technical details, and in Transhuman Space, the encryption is all very strong, making amateur attempts fairly pointless. The characters in the WWII secret agent campaign carefully pass cipher material they capture back to higher authority, but as field operatives they have need-not-to-know about code-breaking on their own side, and are independent enough that they rarely need to talk to HQ from the field.

It's interesting to note how much cryptography there is in the Thaumatology series. I suspect this is because in the modern world, cryptography can seem "magical", pulling information out of nowhere. The occasional crazes for things like steganography fit that pattern.

What have you done with cryptography in a game?