Digital invisible ink

A picture is a grid of colored dots, and the very last bit of each color is a rounding error your eye can't see. Hush writes your message into those last bits, one bit at a time — so the image looks pixel-for-pixel the same, but the words are hidden inside it. Anyone can look at the picture; only someone who runs it back through Hush (with the passphrase, if you set one) can read them. This is steganography: not scrambling a message so it looks encrypted, but hiding the fact that there's a message at all.

How to use it

Hide: drop in any image, type a message (or pick a small file), optionally set a passphrase, and Weave it in. You get a PNG that looks identical — save and share it.
Reveal: drop a Hush image in and it reads the message straight out (asking for the passphrase if it's locked).
Set a passphrase and the message is encrypted with AES-256 before it's woven in — so even someone who suspects and extracts the bits gets only ciphertext.

Honest limitations — read this before you rely on it

Save and send the PNG as a file. The hidden bits survive only in the exact PNG. Messaging apps and social sites that re-compress images (turning them into JPEGs) will silently erase the message. Send it as a file/attachment, or through something that keeps the original.
Steganography is hiding, not armor. Anyone who suspects a stego image and tries the same trick can pull the bits out. The passphrase is what actually protects the contents — use one for anything sensitive (Key Cutter makes good ones).
Capacity is about ⅜ of a byte per pixel — a phone photo holds a novel; a tiny icon holds a sentence. Hush tells you the room before you weave.
The output is always a PNG (lossless); JPEG can't hold the message.

Part of K-Engine Local Tools — free, privacy-respecting utilities that run on your device. The LSB weaver, reader, and AES-256-GCM crypto (via your browser's WebCrypto) are hand-written; view-source and you're reading them. MIT licensed, from the K-Engine workshop · download the source.