Summary
Challenge Description
“Detectivul andre1ut vrea să o ia pe urmele lui Sherlock Holmes. Acesta și-a făcut un cont cu numele de utilizator andre1ut pe platforma de socializare a Cerului Albastru și vrea să îți transmită un mesaj secret. Folosește-te de indiciile primite în cerință pentru a putea ajunge la răspunsul final.”
The goal of this challenge is to conduct a social media investigation based on a username and follow the provided clues to recover the final flag.
Analysis
We are only given a username, andre1ut, and a hint referring to a social media platform called BlueSky.
After searching for the username, I found the following profile:
The profile contained another username, iamsherlockjr, which appeared to be the next clue.
After searching for this username across different platforms, I found an account on Hacker News:
In the account description, there was an encoded message. Looking at the text, it appeared to be encoded using the ROT13 cipher.
After decoding it, I obtained the following message:
1
FLAG-UL REAL ESTE NUMELE PLATFORMEI MELE DE MATEMATICA, TRECUT PRIN SHA256
The description also contained a link to a TikTok account named mathclutch, which is likely the mathematics platform referenced in the decoded message.
Hashing the string mathclutch using SHA256 produces the final flag.
Flag
CTF{37b98a8ea0f2adfea9eb1e9cc3bcce4c8f58187191f40ae1f77916b59e343099}