Third Period - Chemistry
Chemistry was one that we did not solve within the time limit, but we were close. Gigs went back and finished it after DEF CON just to see what the solution was.
The first step is fairly straightforward, the numbers in the text refer to atomic numbers of elements. Replacing the numbers with the atomic symbol yields words to replace the symbols with.
Disfigure a university TEACHER and A+ player
Substitute commander's SHARP: "Chromosomes are made of nucleotides - real and all"
Unsetting SHOCK left without end, colloquially
PLANTS collection is her stick and my stump piece
Travel PLAN for me with minute to take in unusual return
Kid's TV channel SHOWS saint holding back republican Bob for ages
Just right deity sets right INITIAL left by me with bolts
Police SLAY helicopter ejecting hotel chief in favour of taking papa
An appeal AROUND biking
Anal note made fresh for BABES
English cover OF pasta or rice and not one goulash for model
Reinvent Scrabble with French name and small surroundings or CONDITIONS
The next step is less clear, but each line is a clue to a word play that includes the name of an element.
As an example, Disfigure a university teacher (a Don), MAR A DON, MARADON, with Radon as the element.
Some of the word play connections remain unclear, however CryptoK eventually gave all the answers on Twitter. We had gotten some of them prior to that, but not all.
MARADON Disfigure a university TEACHER and A+ player (MAR A DON and Diego Maradona)
PROXYGENERAL Substitute commander's SHARP: "Chromosomes are made of nucleotides - real and all" (PROXY GENERAL, GENE Real And alL)
JARGON Unsetting SHOCK left without end, colloquially (JAR (as in jarring) GON')
HERBARIUM PLANTS collection is her stick and my stump piece (Herbarium, Her Bar)
ITINERARY Travel PLAN for me with minute to take in unusual return (for me =I )
NICKELODEON Kid's TV channel SHOWS saint holding back republican Bob for ages (St. Nick, Bob Dole (backwards), EON=For Ages)
GOLDILOCKS Just right deity sets right INITIAL left by me with bolts (GOD L. LOCKS, by me = I, L is "set left", maybe?)
COPPERP Police SLAY helicopter ejecting hotel chief in favour of taking papa (COP/COPPER=Police, CHOPPER ejecting H= hotel taking papa = add P, phonetic alphabet stuff)
PLEADING An appeal AROUND biking (pleading=court appeal)
NEONATAL Anal note made fresh for BABES (anagram of ANAL NOTE)
CARBONNET English cover OF pasta or rice and not one goulash for model (English Cover=CAR BONNET, pasta or rice = CARB. ONNET=?)
ENVIRONMENTS Reinvent Scrabble with French name and small surroundings or CONDITIONS (surroundings or conditions = environments, don't know about word play part)
From here, CPV did give a clue on Twitter. It was easily misunderstood, though.
[CHM] With answers in hand, the real fun begins! Be sure to save space by representing all elements with their atomic symbol. Once complete, consider where you found that encoded word.
It would be easy to interpret this as referring to the first step, which was replacing the atomic numbers with the symbols. However, it refers to doing it a second time, to the answers, replacing the element names with their symbols.
MARN (MARADON, MA-Radon (Rn), MARN)
PROERAL (PROXYGENERAL Oxygen->O, etc)
JAR
HERBA
ISNERARY
NIODEON
AUILOCKS
CUP
PPBING
NEATAL
CNET
ENVFEMENTS
A hint is that there are 12 words, and all flags so far have been 12 letters.
So we are to select one letter per clue in some way. The tweet says "consider
where you found that encoded word". So we choose a letter index based on the
position of the originally encoded word.
For example:
1Disfigure 2a 3university 4TEACHER and A+ player -> first index is 4. Final solution was MARN, so first letter is "N", the 4th letter.
1Substitute 2commander's 3SHARP, 3rd letter in PROERAL, "O"
Repeating this for each line you get "NOAHSDCUBLES", which is not the flag. But NOAHSDOUBLES is, which I presume was the result of an error in the puzzle.