Password Steg: Encrypt & Decrypt

How to use it in a CTF

The cleanest workflow is two-step: encrypt the secret here, then hide the resulting base64 string somewhere a forensic tool will surface it. Good carriers include EXIF comment fields (write with the Metadata Viewer), PNG tEXt chunks, ZIP archive comments, and bytes appended after a file's logical end. To identify carriers in the first place, drop them through the File Magic Identifier to confirm the format, then look for unused metadata slots.

The ciphertext starts with the four-byte magic psg1 (base64 prefix cHNn) so the decoder can reject random base64 strings before spending CPU on PBKDF2.

Why AES-GCM and PBKDF2

PBKDF2 turns a human-typed password into a 256-bit key by hashing it 200,000 times with HMAC-SHA-256 and a random salt, which slows offline brute force without breaking legitimate users. AES-GCM is an authenticated cipher: a wrong password or a tampered byte fails verification cleanly instead of decoding to plausible-looking nonsense, which matters for CTF use because you want a clear yes/no answer when guessing passphrases.

For full image-LSB steganography, batch decoders, and other CTF-flavoured tooling, see the Steganography Techniques in CTFs post and the Stegall all-in-one solver.