Category:

Crypto
How can you tell the difference between a good cryptography joke and a random string of words?
You can't. They're indistinguishable.

Broken Yolks 50 Points

Fried eggs are the best.
Oh no! I broke my yolk... well, I guess I have to scramble it now.

Ciphertext: smdrcboirlreaefd

Dev: Delphine

Sizzle 50 Points

Due to the COVID-19 outbreak, we ran all out of bacon, so we had to use up the old stuff instead. Sorry for any inconvenience caused...

Dev: William

encoded.txt
66ad1da967199839c7a2c8381054a506

CH₃COOH 50 Points

Owaczoe gl oa yjirmng fmeigghb bd tqrrbq nabr nlw heyvs pfxavatzf raog ktm vlvzhbx tyyocegguf.
Tbbretf gwiwpyezl ahbgybbf dbjr rh sveah cckqrlm opcmwp yvwq zr jbjnar.
Slinjem gfx opcmwp yvwq gl demwipcw pl ras sckarlmogghb bd xhuygcy mk ghetff zr opcmwp yvwq ztqgckwn.
Rasec tfr ktbl rrdrq ht iggstyk, rrnxbqggu bl lchpvs zymsegtzf.
Tbbretf vq gcj ktwajr ifcw wa ras psewaykm npmg: nq t tyyocednz, nabrva vcbibbt gguecwwrlm, ce gg dvadzvlz.
Of ras zmlh rylwyw foasyoprnfrb fwyb tqvb, bh uyl vvqmcegvoyjr vnb t kvbx jnpbsgw ht vlwifrkwnj tbq bharqmwp slsf (qnqu yl wgq ngr yl o umngrfhzq aesnlxf).
Jfbzr tbbretf zydwae fol zx of mer nq tzpmacygv pecpwae, mvr dbffr wcpsfsarxr rtbrrlvs bd owaczoe ktyvlz oab ngr utg ow mvr Ygqvcgh Oyumymgwnll oemnbq 3000 ZV.
Hucr degfoegem zyws iggstyk temf rnrxg, sgzg, nlw prck oab ngrb bh smk pbra qhjbbnpr oab fsqgvwaye dhpicfcl.
Heyvsf my wg yegb ftjr zxsa dhiab bb Rerdggtb hpgg.
Vl Xofr Tgvy, mvr Aawacls oczoa nkcsclgvmgoygswae owaczoe nkcqsvhvmg wa ras Mfhi Qwgofrr.
Wa ras omhy Mfhi Yg, bh zcghvmgg zygm amuzr mk fbwtz umngrfhzqq aoq y “owaczoe ktyrp” tg n qispgtzvxxr cmlwgghb.
Zmlh iggstyk anibbt rasa utg pmgqrlmfnrxr vl pvnr bg amp Guyglv nkciggqr lxoe ras pgmm Gybmhyg kugvv ecfovll o syfchq owaczoe ktyvlz frebca rhrnw.
Foaw Vvvlxgr tbbretff ygr gfxwe slsf dhf psewaykm nlw arbbqvltz cskdbqxg jcks jpbhgcg rbug wa ras nekwpsehhptz zyginj Jwzgg Mnmlvh.
pmqc{tbbretf_bl_fm_sglv_nlw_qugig_cjxofc}

Dev: William
So I was trying to return the stolen archives securely, but it seems that I had to return them one at a time, and now it seems the thieves stole them back! Can you help recover them once and for all? It seems they had to steal them one at a time...

Dev: William

intercepted.txt
17bbbcf788131eeda1c728f5bada7899

returningstolenarchives.py
a8d0b9393d5013ce54d5a1a7c3fb17e6

A while back I wrote a Python implementation of RSA, but Python's really slow at maths. Especially generating primes.

Dev: Tom

chall.7z
36ed4035eb6a0c7a9b2aaa18a5c427ae

Rainbow Vomit 535 Points

o.O What did YOU eat for lunch?!

The flag is case insensitive.

Dev: Tom

output.png
707fe5d5aa9109efcc7d4193d5b0e83f

My math teacher made me do this, so now I'm forcing you to do this too.

Flag is all lowercase; replace spaces with underscores.

Dev: Claire

posthomeworkdeaths.txt
1459c156daa68f0d7bfcc698a18e93e8

Parasite 784 Points

paraSite Killed me A liTtle inSide

Flag: English, case insensitive; turn all spaces into underscores


Dev: Claire

Parasite.txt
ce126723dee2e0ae63ffda0cf2b73202

11 1,527 Points

I wrote a quick script, would you like to read it? - Delphine

(doorbell rings)
delphine: Jess, I heard you've been stressed, you should know I'm always ready to help!
Jess: Did you make something? I'm hungry...
Delphine: Of course! Fresh from the bakery, I wanted to give you something, after all, you do so much to help me all the time!
Jess: Aww, thank you, Delphine! Wow, this bread smells good. How is the bakery?
Delphine: Lots of customers and positive reviews, all thanks to the mention in rtcp!
Jess: I am really glad it's going well! During the weekend, I will go see you guys. You know how much I really love your amazing black forest cakes.
Delphine: Well, you know that you can get a free slice anytime you want.
(doorbell rings again)
Jess: Oh, that must be Vihan, we're discussing some important details for rtcp.
Delphine: sounds good, I need to get back to the bakery!
Jess: Thank you for the bread! <3

Dev: Delphine

edit: This has been a source of confusion, so: the code in the first hint isn't exactly the method to solve, but is meant to give you a starting point to try and decode the script. Sorry for any confusion.

.... .- .-.. ..-. 1,696 Points

Ciphertext: DXKGMXEWNWGPJTCNVSHOBGASBTCBHPQFAOESCNODGWTNTCKY

Dev: Sri