S.T.V. Cipher

Talaisan discovered a hidden video on E.Y.E.'s diary which contains the following text:

SEMI NOUN, I MUST NOW, NEITHER SUM

Talaisan also found the related anagram

MINUS ONE, MINUS TWO, MINUS THREE

This hint was used to decipher various messages by Support The Virus:

• The Virus Puzzle
• Second Support The Virus Comment Puzzle
• Third Support The Virus Comment Puzzle
• S.T.V. email from 19 February
• The Hitman's Gmail Account

Encoding/Decoding

To encode a message using this system, simply use the nth next letter in the alphabet (wrapping at the end of the alphabet) for each letter in the message, where n is the position of the letter in the actual message. For instance, using the message in The Virus Puzzle:

clear text: MANKIND
n         : 1234567
encoded   : NCQONTK

M encodes to N when it is the first letter in the message; it would encode to O if it was the second letter in the message, and so on.
To decode a message encoded with this system, simply subtract the appropriate number of letters from each letter in the message.