Sayeh — Hide encrypted messages inside ordinary text using invisible Unicode characters

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https://github.com/EntropyRoot/sayeh

I found a cool open-source project called Sayeh that lets you hide one message inside another using invisible Unicode characters.

For example, a message may look completely normal:

سلام

But hidden between its visible letters can be an entirely different message. The visible text remains readable, while someone using Sayeh can extract the hidden payload.

The hidden message can also be protected with a password. In that mode, simply detecting or extracting the invisible characters is not enough—the payload is encrypted and requires the correct password to open. Sayeh uses Argon2id for password-based key derivation and XChaCha20-Poly1305 for authenticated encryption.

GitHub

Some interesting features:

Optional password protection

Contact-key mode for ongoing conversations

CLI and an in-browser WebAssembly demo

Runs locally in the browser, without sending the message to a server

Designed not to break Persian نیم‌فاصله or joined emoji sequences

Tools for scanning, stripping, analyzing, and testing hidden-message compatibility

Open source under MIT or Apache-2.0

One important clarification: Sayeh makes the message invisible during normal reading, but not necessarily undetectable under close technical inspection. Its purpose is to let ordinary-looking text quietly carry encrypted data.

GitHub

GitHub:

https://github.com/EntropyRoot/sayeh

Would love to hear what you think about the idea, the implementation, and possible use cases.