Encrypt text with a passphrase
The browser has had a real crypto engine for years. This uses it: no library, no server, no key escrow.
How AES Encrypt / Decrypt works
Hashes and keys are produced with the Web Crypto API inside this page. A hash computed on a server would mean sending the thing you are trying to protect. Verification here is a comparison you can repeat yourself, not a claim you have to accept.
That is the whole architecture: static files, one script, no upload endpoint to leak or log. Close the tab and the work is gone.
Good to know
- Works offline once loaded, including on flights and in locked-down networks.
- No file size limit beyond your device's own memory.
- Free to use, with no account and no usage counter.
- Results are produced locally, so they are not logged or shared with anyone.
Questions
Which algorithm exactly?
AES-256 in GCM mode, with the key derived from your passphrase by PBKDF2-HMAC-SHA256 at 200,000 iterations and a random 16-byte salt. A fresh 12-byte IV is generated for every encryption.
What happens if I lose the passphrase?
Nothing can recover it. There is no key escrow, no account and no reset — that is the point of local encryption.
How do I know the blob was not tampered with?
GCM authenticates the ciphertext. A changed byte or a wrong passphrase fails the check and the tool says so instead of returning garbage.
Is it safe for large files?
This page is for text. For files, encrypt a container with a tool built for streaming — pasting megabytes into a textarea is where browsers fall over.
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