Enter some text and a password to get an encrypted block that can only be read with that same password. Encryption uses AES-256-GCM and runs in your browser.
There is no recovery
If you lose the password, the text goes with it: there is no backdoor, and if there were the encryption would be worthless. Store it in a password manager before encrypting anything you need to keep.
AES-256-GCM with PBKDF2-SHA-256 key derivation at 600,000 iterations, OWASP's current recommendation. Each encryption uses a random salt and initialisation vector, so the same text always produces a different block.
AES-256-GCM is an authenticated symmetric cipher. Symmetric means the same key encrypts and decrypts. Authenticated means that, as well as hiding the content, it detects any modification: change a single bit of the encrypted block and decryption fails rather than returning garbage. That second property is what separates GCM from older modes like CBC.
A password cannot serve directly as an AES key, because it has far less entropy than 256 random bits. So it goes through PBKDF2, a derivation function that applies HMAC-SHA-256 repeatedly, here 600,000 times, following current OWASP guidance. The cost of those iterations is what makes brute-forcing passwords against the encrypted block slow. Each encryption also uses a random salt, so the same password and the same text always produce a different result.
The block you get contains everything needed to decrypt it except the password: a version marker, the salt, the initialisation vector and the ciphertext with its authentication tag, all Base64-encoded so you can paste it into an email or a note. There is nothing to store separately and no server to query.
On what this is not. It is not end-to-end encryption for conversations: Signal or PGP exist for that, with key management and identity. It does not protect the text while it sits in your clipboard or your browser history. And since all the security rests on the password, a weak password makes the encryption irrelevant. There is also no recovery: lose the password and the text goes with it, which is exactly what you should expect from encryption that works.
