AES-256 File Encryptor

This tool turns any file — a photo, a PDF, a zip archive, anything at all — into a password-protected, portable encrypted bundle you can store on a USB drive, upload to your own cloud storage, or send to someone else, and decrypt again later with nothing but the password. Every byte of the work happens inside your browser tab using the native Web Crypto API; the file and the password never leave your machine.

The construction is a standard authenticated encryption (AEAD) scheme, not a toy cipher: a fresh random 16-byte salt and a fresh random 12-byte IV are generated on every single encryption, so encrypting the same file with the same password twice produces two completely different, unrelated outputs. The password is stretched into a 256-bit key with PBKDF2-HMAC-SHA256 at 250,000 iterations — a real, deliberately expensive computation, not an instant pass-through — before AES-256-GCM encrypts the file and appends its own authentication tag.

This is a distinct job from this site's encrypted-notepad tool, which is built for short pasted text kept inside the page. Here the input and output are arbitrary binary files: the salt, IV and ciphertext are concatenated into one small self-contained .enc file with a short header, so the bundle carries everything it needs to be decrypted anywhere, by anyone who has the password — no external key file, no server-side lookup, no metadata leaked about what algorithm or parameters were used beyond what the header itself states.

Decryption re-derives the key from the password and the salt stored in the file's own header, then lets AES-GCM's authentication tag do its job: if the password is wrong or the file has been altered even by a single byte, decryption fails cleanly with a clear error instead of silently returning garbage. There is no recovery path and no backdoor — if the password is lost, the file is gone, which is the entire point of real encryption.