File Encryption Tool (AES-256 with a Password)

Before you put a contract, a tax file or a backup in cloud storage or attach it to an email, you can lock it with a password. This tool encrypts any file in your browser with AES-256-GCM, using a key derived from your password with 600,000 rounds of PBKDF2-SHA256, and stores the original file name inside. Decrypting gives back the identical file with its name. Files never leave your device.

How to use this tool

1. Choose Encrypt, pick one or more files and type a long password twice.
2. Download the .enc files (several are offered as one ZIP).
3. Share the password separately from the files.
4. To open them, choose Decrypt, pick the .enc files and enter the password.

Formula

key = PBKDF2-HMAC-SHA256(password, random 16-byte salt, 600,000, 32 bytes); file = "TSENC1" ‖ salt ‖ IV(12) ‖ AES-256-GCM(key, IV, name length ‖ name ‖ data) ‖ tag(16)

GCM authenticates everything it encrypts, so a wrong password or a single changed byte is detected instead of producing garbage. The output is 52 bytes plus the file name larger than the original.

Example

Encrypting the 26-byte text file sample.txt gives a sample.txt.enc of 6 + 16 + 12 + 2 + 10 + 26 + 16 = 88 bytes. Decrypting it with the same password restores sample.txt exactly; one wrong character in the password gives an error.