Imperial Cipher

An encryption scheme commonly used for encoding messages between parties across Dormelia.

Methodology

In its most basic form, an imperial cipher is more complex variation of a classic Caesar cipher.
Instead of shifting all characters by the same value, the value increases or decreases incrementally with each character, thus better masking the message's contents.
For example, a basic encryption would have the key be shifted by a value of one for each letter that is encoded

Terms and Variables

Key: the value by which a character is shifted along the alphabet Step: the amount by which the key is incremented for each character Plaintext: the original, un-encoded text of the message Ciphertext: the encoded text of the message

Example

Plaintext: I will always love you as I have always declared
Caesar Cipher (key=7): p dpss hsdhfz svcl fvb hz p ohcl hsdhfz kljshylk
Imperial Cipher (key=7, step=1): p ervw mykpoj dhpz uls zs j jdzj gsejid prqaqiww

Strengths

Unlike in a normal Caesar cipher, imperial doesn't make it obvious when the same word or letter is used.
Imperial is also much more customizable given its additional variables. This allows for more complex encryptions to be used depending on the importance or sensitivity of the message.
Such methods used include: Increasing or inverting the step value Using modified alphabets during encoding and decoding processes (ex: acbd, a1b2c3, a!b2c#)

Weaknesses

Imperial can take significantly longer to encode a message depending on the apparatus used given the added complexity.
Also, its cipher text can still hold indicators of patterns:

• A pair of identical coded letters can indicate a pair of plaintext letters that follow after each other (ex: declared = prqaqiww)
• A pair of coded letters following after each other can indicate a pair of plaintext letters that are identical (ex: will = ervw)

These pattern weaknesses can be mitigated by use of customized rules such as those listed under Strengths, but this also has the potential of lengthening encryption time. Also rules such as customized alphabets include additional complications such as how to send said alphabet to the receiver.

Common Uses

The basic cipher is popular amongst nobles for encoding their personal correspondences between friends and acquaintances. 
More complex variations of the cipher are typically reserved for sensitive topics such as military orders to troops.

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