BKISC 2026 Cryptografie: Java AltBase64 over UTF-16 BE
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. ...