REPLY CTF 2020

Wells Read — Coding 100

In the challenge we download a zip file which contains two text files:

  • A dictionary (a file which has one word in each line)
  • The book: “The Time Machine”

Now we can see that some words got “scrambled” in the book, looking at a few example we can see that they all have the same characteristic:

Only on character was replaced!

This is great news, it means that we’re looking for words that are not in the dictionary file with Levenshtein distance of 1 from a word that is in the dictionary.

Coding it is not difficult (written in nodejs):

Now we can search the output for the string and we’ll find the flag:

I was able to find another couple of good write-ups about other challenges in Replay 2020:

Enjoy!