Encoding

Platform THCON 2026 (Toulouse Hacking Convention) Difficulty Medium OS Steganography Tags Frequency analysis, binary encoding, PNG carving, LSB steganography PNG3D is the steganography challenge that rewards the simplest possible recon move — frequency analysis — and punishes anyone who tries fancy stego tools first. The challenge file is ~40 MB of UTF-8 text that looks like noise; the trick is to notice that two specific characters make up nearly all of it, in roughly equal numbers, and that’s a binary encoding screaming to be decoded. ...

Platform BKISC CTF 2026 Difficulty Easy OS Encoding Points 50 Tags JDK source reading, custom Base64 alphabet, UTF-16 BE Cryptografie is a 50-point crypto challenge from BKISC CTF 2026 that hangs off a single, very specific hint: FileSystemPreferences.dirName(). If you’ve never had to look at the OpenJDK source before, this challenge is a tour of an internal Base64-like helper that almost nobody outside the JDK uses — and the decoder only takes about ten lines once you know where to look. ...