pain

The Most Worthy Distinction of Pain

Level: Hard

Description:

We intercepted a code:

encrypted.txt

Yeah, so, this is a lot of nonsense. It's mostly words that start with d, but at least we know how it was created?

encrypt.go

We also know where the dictionary file came from: CROSSWD.TXT

Note: The CROSSWD.TXT file can be verified with an md5 hash of e58eb7b851c2e78770b20c715d8f8d7b. It starts with 1st word aa, and ends with the 113809th word zymurgy.

Writeup

This challenge takes in text, combines each two letters pairwise, gets their combined encoding, and gets that nth word from the dictionary. As it turns out, that's mostly the ds of this particular dictionary.

It can be solved by taking each word, finding its position in the dictionary, taking the 0xff00 mask for the first letter the word represents, and the mask 0x00ff for the second letter.

Flag - byuctf{what_an_inefficient_code_ug2Ko8Cz}