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WARNING To all Newcomers,
as old hands will testify this yearly competition can be addictive fun!!
Please keep a check on your mental health, especially on the last 10B challenge.Muahaha, Harry
Tip: Nothing gets solved by staring at it for hours, walk away from it for a while and
then return with a fresh mind, sometimes that helps a lot!Good vibes every one.
Hello! For those who want tips I just want to say try your best and don’t worry if you don’t get it! Last time my team got really stuck, so we took a break and solved it afterwards. It always best to get as many points as possible, but if you lose some, don’t worry! These puzzles are designed to challenge, but always remember to have fun!
Perhaps it could stand for:
This Enigma Machine, Please Encipher Secret Texts?
You really ought to set a character limit for the display name. My display name is the entire Shrek script.
There’s always one! If you don’t mind me saying so, that is something you might be able to fix for yourself. I will mention it to the web team. Harry
btw i would just like it to be known (since no one i know irl wants to listen to me ranting ;-;) that for this challenge i:
1. screwed up my sleep schedule
2. started doing this at school and now my friends (and perhaps teachers) think i have no life 🙁
3. may have failed my bio test (and i plan to become a doctor??? wishful thinking lol) (idk i think i didn’t do bad?? but like maybe not full marks)
and most importantly 4. i missed my advent calendar yesterday and i didnt realise until my sister told me D:anyways so this competition is very fun and definitely okay for your mental health!! just uh… maybe tell your parents to set a screen time?
😛 yeah if you’re stuck just rage for 10 minutes, watch a youtube video or something and then come back!! Might help.
-RTime for me to say: “Muahahah”. Harry
Okay, I have missed 3 deadlines, attempted thousands of attacks, written six programs in 3 different languages, yelled a t people, taken a 25 hour brak and I’m giving up. Have a nice life. 😭😭😭😭😭😭😭
Sorry to see you go, you had a good run. Enjoy your rest-we hope to see you back here next year. Harry
@rl0r_g1rl
Reading your post reminded me of myself a few years back! I ended up working alone after challenge 7 as my friends/teammates decided to ‘get a life’ and do other things instead, but I found greater joy in sticking with the challenges, so that became my version of “life” every Thursday at 3pm until late…
Just remember, the challenge only runs till December/January and you have roughly a week between each one, so you’ve got plenty of time after that to catch up on bio tests! (Not that this is me justifying not revising for exams… but know that you’re definitely not the only one who’s screwed up sleep, exams, or routines because of this, it’s all part of the fun experience!)
Dont rlly know where to put this out of curiousity which team has been doing this the longest
Harry,
Can you PLEASE tell us what T.E.M.P.E.S.T. stands for after the challenge finishes
p.s. pleaseWe shall see! Harry
Idk, chapter 9b is so hard. We’ve literally missed 2 deadlines and still don’t know what to do.
Don’t get too discouraged. There are six deadlines after all! Harry
TEMPEST is actually a codename used by the US government and NATO for investigations and standards related to spying on electronic emissions, basically preventing electronic eavesdropping. Given the context of Dickens visiting US it could potentially link to that? But in the case for the forum the letters are spaced by dots, which suggests some kind of acronym?
The actual backcronym T.E.M.P.E.S.T. derived from the NATO codename stands for Telecommunications and Electronics Material Protected from Emanating Spurious Transmissions (or something along those lines). It is ironically titled such as Harry and Jodie are actively stopping the leaking of hints and such in the Forums. They are literally our EMSEC (Emission Security)…
Can anyone please explain how challenges 9a and 9b were encrypted and broken?
Over to you lot! Harry
@atharvdagoat 9a was encrypted with a Vigenère cipher using the keyword “TRAITOR”, and then reversed.
I broke it by first using a program I wrote that computes the periodic index of coincidence (pioc).
Supposing the period (keyword length) was 7, I would compute the IoC of a slice of the first character in every block of 7, and then the second, the third, and so on. This gives me 7 IoC values which I take the average of. Since each 7th letter is encrypted using the same (caesar) shift, this average IoC value (pioc) was 0.06440, which tells me that this is the right period.
Of course, I didn’t know the period ahead of time, so my program plots the pioc values for each period, and I took the first promising one. This works the same even when the text is reversed.
To be honest, I just tried to solve it as a normal Vigenère, noticed that didn’t work, then guessed it was reversed. A more analytical approach would be to solve the Vigenère as a bunch of independent Caesar ciphers (using single letter frequencies), then recognise the reversed words in the plaintext. The title of that challenge was “The Upside Down” (I approve 🙂 ) which was probably intended as a hint that the text was reversed.
9b was a Playfair cipher using atypical rules. Playfair uses a grid like this one (the key for 9B):
`
C O M P A
N Y B D E
F G H I K
L Q R S T
U V W X Z
`It encrypts letters in pairs. The encryption rules used in this cipher were as follows:
- If the two letters you want to encrypt are the corners of a rectangle in the grid, take the other two corners. Each letter in the pair gets encrypted to the other corner in the same row.
- If the two letters are in the same row or column of the grid, encrypt each letter in the pair to the one on its right (wrapping around at the end).
So, if we look at the first few letters of 9b’s plaintext “CH AR LE SI” and ciphertext “MF MT TN RH”.
- “CH” forms the corners of a rectangle, so we take the other two corners: “MF”
- Likewise for “AR”
- Likewise for “LE”
- “SI” are in the same column, so we encrypt to the letter to the right of each one: “RH”
Decryption is performed by doing these same rules in reverse.
I solved this using an automated program which uses a similar approach to the algorithm Madness describes in their book. My program occasionally tries changing the rules for letters in the same column and row, so was able to solve this cipher.
You don’t need a program to break it though. As you probably noticed, the plaintext contains a bunch of X characters to break up repeated letters. The ciphertext contains no pairs of letters with repeats (out of the pairs starting at an even index in the ciphertext), it also only has 25 letters in its alphabet; these two facts tell you with pretty high confidence that it’s a Playfair cipher. You can then try to break it by looking at the most frequent pairs of letters (at even index); this will most likely be “TH”, “AT”, “HE”, and so on. Beyond that, you can look for cribs: “CHARLES”, “DICKENS”, and “LORD DERBY” are some good ones. Once you have one correct guess you get more and more letters, both in the plaintext and in the grid, and eventually you solve it.
You could also do a keyword search. As you can see, the alphabet is keyed with “COMPANY” (it appears that if you were following the content of the messages more closely there was a hint about this keyword in a copy of A Christmas Carol, I was not paying enough attention to notice this). There are three major strategies for filling a grid based on a keyword: “COMPANYBDEFG…” (go back to start of alphabet), “KEYWORDFG…” (continue from last letter of keyword), “CIPHERSTUVW…” (continue from max letter in keyword). You can try them all with a word list.
While it would have been tricky to guess the exact rule used in a keyword search, the majority of pairs (64% assuming uniform distribution) are encrypted using the rectangle rule, which is unchanged. So you would most likely have found the correct keyword, and then you could just go through the text by hand and figure out Harry’s trickery.
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