securefilelock.com

● Runs entirely in your browser

Lock a file to this exact device. Nothing else can open it.

SecureLock encrypts your PDFs, images, and ZIPs with a key derived from your device's public IP address. No uploads, no accounts, no servers to trust — the math does the locking.

Open SecureLock Web → See how it works

🔒 AES-256-GCM 🌐 Zero uploads 🧩 No account needed

This device's public IP fingerprint

203.0.***.***

📄 quarterly-report.pdf Locked ✓

How it works

Three steps, no waiting rooms

Everything happens locally in your browser tab — there's nothing to install and nothing to upload.

01 / fingerprint

We read your public IP

SecureLock looks up your device's current public IP address the moment you choose a file — this becomes the raw material for the encryption key.

02 / derive & encrypt

A key is derived, never stored

Your IP is combined with a random salt through PBKDF2 (480,000 rounds) to produce a one-time AES-256 key. The key exists only in memory, briefly.

03 / lock

Your file becomes a .slk container

The encrypted file downloads straight to your device. It will only decrypt again on a browser reporting that same public IP.

Built for one job

What SecureLock does well

It's not a general-purpose vault — it's a single, sharp tool for single-device file protection.

🗂️

PDF, JPG, and ZIP

Purpose-built for the file types people actually need to lock down: documents, images, and archives.

🚫

Nothing leaves your device

Encryption and decryption happen in your browser with the Web Crypto API. Your files are never transmitted anywhere.

🔑

No accounts, no passwords to lose

There's nothing to sign up for and no password to forget — your network is the credential.

⚡

Instant, no install

Open a page, drop a file, done. Works the same on Windows, macOS, and Linux.

🧾

Readable audit trail

Every lock and unlock attempt is logged in plain language right in the interface, so you always know what happened.

🎨

Three themes

Light, Dark, and Midnight — pick what's easiest on your eyes, day or night.

The technical part

Enforced by math, not an "if" statement

Most IP-restriction tools just check the IP and then decide whether to proceed — a check that can be patched out. SecureLock ties the IP directly into the encryption key.

Why this is harder to bypass

The decryption key is derived from the public IP address itself, using PBKDF2-HMAC-SHA256. If the current IP doesn't match the one used at lock time, the derived key is simply wrong — AES-GCM's authentication tag fails to verify, and decryption is mathematically impossible, not just refused.

AES-256-GCM authenticated encryption
PBKDF2-HMAC-SHA256, 480,000 iterations
Random salt + nonce generated per file
No master key, no backdoor, no recovery bypass

// lock

saltrandom(16)

keyPBKDF2(ip, salt)

file'AES256‑GCM(file, key)

// open

key'PBKDF2(ip_now, salt)

ip_now == ip ?decrypt ok

ip_now != ip ?tag fails

Good to know

Frequently asked questions

What happens if my IP address changes? +

The file can't be recovered. Because the IP itself is the key material, there is no password fallback or master key — this is intentional, but it means SecureLock is best for short-term, single-network protection, not long-term archival.

Can someone on the same office Wi-Fi open my locked file? +

Possibly — the lock is tied to the shared public IP of a network, not to one specific person or device. If you need it tied to one exact machine or account, that requires an added hardware-ID or login layer on top.

Do I need an internet connection to use it? +

Yes, both to lock and to unlock — SecureLock needs to look up your current public IP each time, even though the encryption itself happens locally.

Is my file ever uploaded anywhere? +

No. The only network request is a lookup of your public IP address. The file itself never leaves your browser.