AES-256-GCM
The default, and the right answer unless you have a reason. Authenticated, fast, and hardware-accelerated on every CPU made this decade.
What it is made of
- Key size
- 256 bits
- Authenticated
- Yes — the cipher produces its own tag
- Nonce
- 12 bytes
- Runs in
- Your browser and the server
What it is
The default, and the right answer unless you have a reason. Authenticated, fast, and hardware-accelerated on every CPU made this decade.
Where it runs
Both lanes. By default the lab runs it in your own browser over the Web Crypto API, so nothing leaves your device — there is no upload, no size limit and no queue. The server lane is there when you want it, and it is the only way an agent or a script can reach the same engine.
What it does not protect
A cipher protects the CONTENT and not the shape. The length of the file, the moment you sent it and who you sent it to all survive encryption untouched, and no setting on this page changes that. The container header is plaintext too — it records which cipher you chose, which is correct and deliberate, and it records the original filename only if you explicitly ask it to.
Try it
Open the lab, pick this in the cipher list, and encrypt the same file twice. The two results share no bytes — that is the random salt and IV doing their job — and both open with the same passphrase. The lab is a Leumas membership away; everything on this page is free.