Memorable passphrases of 4 to 8 random words from the BIP39 English list.
AES-GCM Encrypt / Decrypt
Runs locally
Use AES-GCM Encrypt / Decrypt
What it does
Encrypt text with AES-256-GCM and a passphrase, or decrypt a Base64 string made by this tool. The key is a single SHA-256 hash of the passphrase, so use a long random one.
It runs entirely in your browser: nothing you enter is uploaded.
Example
Short message
Meet at the usual place at 10:00.sc/i5ncy6JbuW/+WPWQo6pboxhwf1K3tR7fOW49jHPXbZOVhlKrJEXqGkWJ31PqgI7moKwETaLovN0/tlA==Encrypt returns Base64 of a random 12-byte IV, the ciphertext and the 16-byte tag, different on every run. Type a passphrase in Password / Key first: the tool also accepts an empty one, which protects nothing.
FAQ
How is the key made from my passphrase?
The AES-256 key is one SHA-256 hash of the passphrase, with no salt and no slow key derivation such as PBKDF2 or Argon2. A short or guessable passphrase can therefore be brute-forced quickly offline, so use a long random one, for example from Passphrase Generator.
What is in the output, and can other software decrypt it?
Base64 of a random 12-byte IV, then the ciphertext and the 16-byte GCM authentication tag. Decryption shows Error: wrong key or invalid data if the passphrase is wrong or any byte changed, and other software can decrypt it only with the same SHA-256 key and byte layout.
Is my text or passphrase sent anywhere?
No. Encryption runs in your browser with the Web Crypto API; the passphrase and the text are never uploaded or stored.