Porphyria's Glomschal Challenge

From LSWiki

A Challenge

Porphyria has one too many glomschals! Help her out by solving a puzzle, and taking one off her hands. The challenge: Since glomschals assist in hiding people in plain sight, the challenge is to decypher the following block of cypher text:

NFIIV TMVRVSN TIQXIR DTLHE EXALS RXZ NGVB OIMKP CG YEMGRS TYXFHTL SBOX WGPXB BAUXVO EOPTVJ

A few rules, hints, and other goodness...

• The plain text is in plain English, relatively standard grammar, with all punctuation removed and should make some sense if properly decoded.
• You may make as many guesses as you like, but be reasonable. I'll know if you're close or if you're just guessing, and reserve the right to ignore anyone who makes too many silly guesses.
• The plain text is relatively easy to decode with a pen and paper if you know the rules. It is a relatively simple cypher which can be decoded, and hopefully by somewhat-intuitive methods, not a one-time-pad, a page from the Voynich Manuscript, or any other undecypherable shenanigan. You will not need your Nazi grandmother's Enigma Machine, so put that back in her boudoir where you woke up next to it this morning.
• I will give hints when I damn well feel like it, and only on here, so don't ask for any, goddamnit, and check back here often.
• Feel free to work together on this, but there is only one glomschal, so figure out amongst yourselves who gets it. Post-award bickering will be met with slaughter and scavenger hunts.
• First in-game tell or mud mail to me with the right answer wins. In the event of a tie, I flip a coin. If the coin lands on its edge, I divine the winner via cromniomancy.

• 10/8/11 2:43 PST - I have checked the code, and I did make some mistakes, although most of it was correct. As I said previously, the original cypher would have been at least mostly-decodeable, but would have seemed to contain spelling mistakes (which it did - my bad). This will teach me to write this shit when I'm sleep-deprived.

FURTHER HINTS:

• Every letter is significant in decoding the plaintext. There are no 'filler characters' you're not supposed to take into account.
• It is not a ROT-based cypher.
• The cypher-to-plain text will not require rearranging the letters as an additional step (the plain text is not an anagram of some middle-step cypher). Basically, only one method was used to encrypt this.
• If you know something about old advertisements, the message may be familiar to you.
• An important part of decoding each letter is the letter that comes before it.
• Man Army, Ram Myna!
• There aren't as many letters in the decoded message as there are in the cypher.
• The hint before the last one is an anagram. If you know what it refers to, you should be able to figure out what product the text is an advertisement for.
• Think roadside advertising.
• The 9th word is "I". If you can figure out how CG makes I, you should have a good idea how to solve this.

And for those who are actually still paying attention to this, your reward for giving a damn is a heads up: My next contest will be a scavenger hunt, timed roughly to coincide with the week before Halloween. Some details may be found on my blog (and here later).

And we have a winner: Rashidun, who sent a mud mail @Date: Sat Oct 15 17:44:14 2011.

The decoded message: Said Farmer Brown who's bald on top, "Wish I could rotate the crop." Burma Shave

Congrtulations to Rashidun, and stay tuned for the next challenge.

Finally, (since someone asked), the encryption was done by picking a Scrabble letter out of a bag for the first letter of each word. After that, the following letters were indicative of how many letters in the alphabet each letter appeared after the last one, with A=0, B=1, C=2, and so on. So, "CG" indicated I because I is 6 letters after C in the alphabet. I'm not really that knowledgeable about cyphers, so I don't know the technical terms for what this kind of cypher is called, or anything -- it was just something I dreamed up.