Cryptology

(Int) Trained Only

Cryptology is the art of creating and cracking codes designed to hide the content of a given message. A character with this skill can create or break codes, or decipher a message from code.

Code Keys & Key Objects: All codes have a Key, it is the Code Key that is used to decode or encode a message. All Code Keys are represented by a Code Name and the Code Level, eg: JN25 Lvl:30 for 25th Japanese Code, Level:30. All code keys are kept in an object for use when encoding or decoding messages, the type of object these code keys are kept in relates to the level of the code. Level 1 to 20 use Code Cards, levels 21 to 30 use Codebooks, levels 31 or greater use machines (including Operator Manuals) such as the enigma machine. Losing a code key object is a very serious problem as enemy agents could use it to decrypt messages enciphered in the stolen code!

Encoding a Message: A message can be encoded with the use of a code key, the character simply transcribes a copy of the message into code (hand written or typed page). The Game Master makes a DC16 skill check in secret to see if the character makes any errors in encoding the message, if failed the encoded message contains errors and any attempt to decode it will automatically fail – the decoded message will be badly garbled and unintelligible.

The encoded message can then be sent by dispatch rider, or transmitted by radio.

Game Master Note – it is a good idea to note down the name of the code and the codes level with notes about the message.

Decoding a Message: An encoded message appears, as a jumble of letters and numbers, the message must be decrypted using the correct code key before it can be read. First the character must select the correct code key to decipher the message; normally Cipher Clarks will have an Operations Manual that lists which codes are used on which days for friendly messages. If the character does not have access to this information the character must pass a skill check to identify the code in use in order to select the correct code key for decrypting the message. The skill check is DC22 for Friendly codes, and DC26 for Enemy codes. Passing the check only identifies the code key required to decrypt the message, failing means the character cannot determine which code key to use (although a character could try each code key available, but this will take time).

Decoding a message with the correct code key is a DC16 skill check; if the skill check is failed the character has made an error in decryption and must start again – using the wrong code key results in automatic skill failure.

Breaking into a Code: In order to read enemy messages the character will have to “break into” the encrypted code used to encipher the messages.

The DC to break a code is equal to the code level +10, and requires a minimum of 2 hours research per code level. If the skill test fails the character can test again after an extra 8 hours of research (once per day), each extra day of research gives a bonus of +1 to the roll.

Capturing certain items gives a bonus to the roll:

A successful skill test has resulted in the character breaking into the code and understanding how it functions to cipher a message. For level 1 to 20 codes the character has created a set of Broken Code Cards, for level 21 to 30 codes a set of Broken Codebooks have been created – these Broken Code Key Objects can now be used to decode (or encode) messages as per normal.

Messages enciphered on a machine cannot be broken by Cipher Clerks in the field.

Creating new Level 1 to 30 Encryption Codes: A character can invent a new code with a code level up to the characters skill ranks plus 4 (maximum code level 30). To create the new code the character must spend 1 hour researching the new code per code level, at the end of that time the character must pass a skill check with a DC equal to 6 plus the code level. If passed the character has created a code key & code key object (levels 1 to 20 are code cards, 21 to 30 are codebooks).

This new code object will need to be copied and sent to each character expected to decode or encode messages in the new code.

Synergy: A character with the Studious feat gets a +2 bonus on all Cryptology checks.

Encryption Code Machines

Messages enciphered on encryption machines such as the famous Enigma Machine are far more complex than hand ciphered codes, and require considerable resources to break into and decode in a timely manner where the decoded messages could be acted upon.

For example, the cracking of the Enigma Code was first accomplished in 1932-33 by the Polish Cipher Bureau under the leadership of mathematician Marian Rejewski. Rejewski developed a machine that could recreate the wiring pattern of the code wheels inside an Enigma machine with the help of Enigma operating manuals provided by the French Secret Service.

But in 1939 - with the impending German invasion of Poland - and German changes to the Enigma machine itself (which rendered Rejewski's devices obsolete) - the Polish code breakers fled to the United Kingdom. Handing their research over to the British who established the Ultra Program at Bletchley Park under the leadership of Alan Turning.

It was not until 1940 that Bletchley Park was able to break into the German Airforce and Army Enigma cipher, while the all important German Naval signals cipher was finally cracked in 1941. Which enabled the British the ability to pinpoint German U-Boats in the Atlantic hunting merchant ships bringing vital supplies to the United Kingdom.

Although the Enigma Machine was a technical marvel for it's day, operation of the machine was rather simple. The operator employed a Operators Manual that provided instructions for how the plug board and rotor wheels should be configured before encoding or decoding a message for a given day and time.

Encoding or decoding a message was done by typing each letter of the message onto the keyboard at the front of the machine. As each letter was typed, a replacement letter was highlighted on the top of the machine. All the operator had to do was note down the replacement letters.

Thus a simple clerk didn't need to know how the encryption worked in order to encode or decode a message, they simply needed to know how to configure the Enigma Machine for a given time period. This information was held in the Operators Manuals, which German Signals Operators were under strict instructions to destroy at the first sign of any chance the books could be captured by the enemy!