What it does

Text is encrypted with AES-256-GCM, an authenticated cipher — meaning it protects the content and also detects tampering, so a modified ciphertext fails to decrypt rather than producing garbage.

The key comes from your passphrase via PBKDF2 with SHA-256, 200,000 iterations. A random salt and initialisation vector are generated per message, so encrypting the same text twice with the same passphrase produces different output — which matters, because identical output would reveal that two messages are the same.

The result is base64, so it survives being pasted into an email, a chat or a document without corruption. All of it runs in your browser through the WebCrypto API; the text, the passphrase and the ciphertext never reach a server.

The passphrase is the weak point, not the cipher

Nobody breaks AES. What they do is guess passphrases, and the iteration count only slows each guess — it is a speed bump, not a wall.

So strength here means length and unpredictability, not decoration. A passphrase of four or five unrelated words is far harder to guess than a short one with letters swapped for symbols, because every additional character multiplies the space to search while a predictable substitution barely adds to it.

And the corollary people miss: a passphrase you cannot remember, written down beside the ciphertext, protects nothing at all. If it lives in the same place as the message, it is not a secret.

The channel matters as much

Sending the ciphertext and the passphrase through the same channel defeats the entire exercise. Same email thread, same chat window — anyone who can read one can read both, and you have added inconvenience rather than security.

The passphrase has to travel separately, and ideally not in writing: agreed in person, or said aloud on a call.

What this is and is not for

It suits a note you want to keep out of plain sight in a shared document, or something moderately sensitive going to a person you can telephone.

It is not the right tool for credentials, financial data, or anything with legal consequence. Password managers and purpose-built systems handle key storage, rotation, sharing and recovery, and none of that exists here. Saying so is not a criticism of the tool — it is the difference between a lock on a drawer and a safe.

There is no recovery

Lose the passphrase and the text is gone. Nothing about it is stored anywhere, so there is no reset link, no support address and nobody who could help even in principle. That is a property of the design rather than a gap in it.

Which means one habit is essential: before you delete the original, decrypt the ciphertext once and confirm you get the text back. A typo in a passphrase you only entered once is indistinguishable from a wrong passphrase.

Hashing is the neighbouring idea and the opposite operation — a file hash proves something is unchanged and can never be reversed, while encryption hides content and is meant to be reversed by whoever holds the key.