How to encrypt a file with a password
- Drop a file onto the box (any type: PDF, photo, spreadsheet, ZIP), or type a secret message.
- Choose a strong password, type it twice and press Encrypt. Download the
.bmencfile, or copy the encrypted text. - Send or store the encrypted file anywhere. Share the password by a different channel, such as a phone call.
- To open it, choose Decrypt, drop the
.bmencfile (or paste the text), enter the password and download the original, with its original file name.
How the encryption works
Your password is stretched into a 256-bit key with PBKDF2-SHA-256 and 600,000 iterations, the level OWASP recommends, using a random 16-byte salt so the same password never produces the same key twice. The file is then encrypted with AES-256-GCM, the same authenticated cipher used in HTTPS and modern messaging apps. GCM also detects tampering: if a single byte of the encrypted file is changed, or the password is wrong, decryption fails instead of producing garbage.
Everything happens inside your browser through the built-in Web Crypto API; files are never uploaded, so this works for confidential documents. The security rests entirely on your password, because there is no back door and no recovery: a forgotten password means the file is gone. Use a long passphrase of four or more random words. Very large files (over a few hundred megabytes) may exceed the memory available to the browser tab.
Can someone open the file without this website?
The format is documented: a "BMENC1" header, iteration count, salt and IV, then AES-256-GCM ciphertext. Any developer can decrypt it with standard libraries, and this page also works offline once loaded.
What if I forget the password?
The file cannot be recovered. There is no reset, by design.
Is AES-256 secure?
Yes. AES-256 is approved for top-secret information. The weak point is usually the password, so make it long and unique.