Tools / Password Steg
Password Steg: Encrypt & Decrypt
Type a message and a passphrase to get back a base64 ciphertext you can hide in any carrier: an image comment, a PDF metadata field, an EXIF tag, a Discord paste, or a steganographic LSB embed elsewhere on this site. The recipient pastes the ciphertext back in with the same password to recover the original.
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How it works
Encryption uses PBKDF2 (HMAC-SHA-256, 200,000 iterations, random 16-byte salt) to derive a 256-bit key from the password, then AES-GCM with a random 12-byte initialization vector to encrypt the message.
The output is base64 of magic || salt || iv || ciphertext. The magic prefix (psg1) lets the decoder reject random data fast. AES-GCM's authentication tag means a wrong password (or tampered ciphertext) fails cleanly instead of returning gibberish.
Everything runs in your browser via the WebCrypto API. Nothing is uploaded.
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.