YOU HAVE TO HELP!
I was time traveling with Fred last week - you know Fred, he's a nice guy - when we got separated. His hand-held automatic chronological portal manipulation and guidance unit (HHACPMGU) (we're working on a better name) malfunctioned! We were eating ice cream with Richard Feynman and talking about our latest visit to Sumer when Fred's pocket vibrated, the wormhole opened, and he was gone!
I raced home - time, not space - because our contingency plan was always to leave a message is a particular secure location so that the other could retrieve it in our home time. Fred wasn't waiting for me so I knew his remote couldn't get him home and he needed me to come save him. I dug in the exact coordinates that we'd agreed upon and found a small metal box. It contained a sheet of metal with an encoded message engraved on its surface. I had tried to tell Fred that there was no way that anybody would ever find the message should we ever need to send one but he was always more paranoid that someone would discover our time traveling secrets.
Now, because Mr Paranoid went and got himself stuck in the past, I have to try to decode this thing so I can go rescue him. Knowing him, it isn't even a direct message. It's probably just something related to where / when he is. It doesn't matter how long it takes to figure out - time traveler, remember? - but I have to get it done or Fred is stuck!
When and where should I meet Fred?
I have a busy weekend planned so I wanted to get this information out there before it started. You'd think I could free up some time with my HHACPMGU but you have to be really careful about not running into yourself in the past. Fred and I used to travel with Kevin until The Incident. That took forever to clean up. Poor Sally, too, left with all those kids... Anyway, that's why I don't use the HHACPMGU for such trivial things so I don't have as much time to try decryption this weekend. I hope you can still help!
I found another box under the first one with a plaintext message! I guess Fred knew I would never solve this without at least knowing where to start. The message told me that the decrypted text would only include uppercase alphanumeric characters. I probably would have guessed that by myself so it's a good thing that the message also said that the encrypted version is longer than the decrypted version. It didn't say how much longer, though, because I guess Fred is more of a paranoid jerk than I thought.
I manged to find some time this weekend - despite all that's happening - so I could check in on the progress. A comment from Ian MacDonald got my attention. I did a quick analysis of character frequency and I got some weird numbers. There is something definitely going on here...
A 17%, B 22%, C 4%, D 4%, E 4%, F 3%, G 4%, H 3%, I 3%, J 3%, K 2%, L 2%, M 3%, N 3%, O 2%, P 2%, Q 2%, R 3%, S 2%, T 2%, U 2%, V 2%, W 2%, X 1%, Y 2%, Z 1% Not only do these not line up at all with a typical character distribution, but there are way too many As and Bs
An amazing thing happened last night. A Western Union delivery man shows up on my doorstep with an old, weathered envelope. He says that they've been holding on to this letter for a long time with specific intructions on when and where to deliver it. In fact, the office even had a bet going on whether or not I'd even be here. The delivery guy had lost the bet, it seems. I figure this must be a letter from Fred so I rip open the package and pull out a single sheet of paper with the following message:
I am a programmer. I use zero-based numbering. Z = 25
Well, I'm not a programmer, Fred! Now I have to go lookup what you're talking about. I was going to ask the Western Union delivery guy exactly how long they've had this letter as that would answer half my question but he was already gone. I suppose he was upset about losing the bet.
Ah, well. Back to work, I suppose. How does this work with the "every third letter" pattern that Tryth found?