Nullkey

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Encrypt messages and files

Disposable encrypted messages. Exchange a fresh receive link, then share through any app.

Encrypted locally. No uploads. Works offline.

X25519 + ML-KEM-768AES-256-GCMML-DSA-65

Help & details

  1. Exchange a receive link

    In Decrypt, create a receive link and share it with one sender. Keep that tab unlocked. Compare safety emoji once to verify your identities.

  2. Write, then encrypt & copy

    Press Ctrl ↵Tap Encrypt & copy, then paste the copied link into any chat, email or post. You can also copy ciphertext or save a .cipher file.

  3. Decrypt once

    Paste their ciphertext into the original receiving tab. Its one-time key is erased after decryption. Create a fresh link for the next message.

Files work the same way. Drop one on the page to get an encrypted .cipher file you can attach in your chat app; its real name and type are hidden inside.

If you prefer the share menu, install Nullkey from Chrome's menu on Android. Then, in apps that offer sharing, choose Share → Nullkey to open an encrypted message or .cipher attachment. Availability depends on your browser and device; on iPhone, use message links or paste instead.

About your public key
Made for you
Your browser creates it the first time you visit. There's nothing to sign up for.
Safe to share
Your public identity verifies signatures and stays the same across receive links. Each new message needs a fresh receive link with its own private key, held only in the receiving tab.
Saved in this browser
Clearing your browsing data deletes it. To keep a backup, or to use it on another device, copy a identity backup from My keys. Backups never include one-time receiving keys or recover disposable messages.
Security details
Encryption
AES-256-GCM, with a fresh key for every message (HKDF-SHA-256, random 128-bit salt).
Quantum resistance
New message keys combine ephemeral X25519 with one-time ML-KEM-768, designed to resist known quantum attacks. This depends on the algorithms remaining secure; it is not a guarantee against every future breakthrough.
Sender
New messages use ML-DSA-65 sender signatures. Verify the full Nullkey ID and safety emoji to authenticate its owner.
Key erasure
Disposable receiving keys are erased after a successful open, or on lock/reload. Later identity-key theft cannot reconstruct them. Browser memory erasure is best effort.
Safety emoji
10 emoji from a set of 256: 80 bits of SHA-256 over your whole ID, too many to fake.
Integrity
Any change, reorder or cut to a message or file makes it fail to open.
Network
None. The page's security policy blocks every outgoing connection, and it works offline.
Code
The browser's WebCrypto, plus pinned local noble ML-KEM-768, ML-DSA-65 and Argon2id implementations.
What it can't hide
  • Your chat app still sees that you sent something, when, to whom, and roughly how long it was.
  • New messages use independent one-time receiving keys, erased after decryption or locking. Identity backups cannot recover them. Older v2/v3 messages retain their original security properties.
  • A platform can keep ciphertext forever. Key erasure protects against later identity-key theft; it cannot guarantee safety if the underlying cryptography is eventually broken.
  • You trust this page each time it loads. If your device itself is compromised, no encryption can help.
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Private, encrypted messages over any app

Type a message in Nullkey and press Encrypt & copy. Paste the result into any chat app, email or post, like any other message. That app, and anyone watching it, only sees scrambled text. The person you chose copies it into their Nullkey to read it.

You both need Nullkey open in a browser. There's no account, and nothing you write is sent to any server.

Protect your private keys

Set a passphrase to save encrypted keys in this browser, or keep them only in this tab.

Use at least 12 characters. It cannot be recovered if forgotten.

Protect keys

My keys

Share your public key; keep your private keys secret. Choose how to protect them below.

Public key

Safe to share

Your Nullkey ID verifies your identity and signatures. New messages need a fresh receive link; one-time receiving keys are erased after use.

SHA-256 fingerprint

Generating…
Verify key with fingerprint emoji

    These emoji are a fingerprint of your public key. Anyone who adds you sees these same 10 for you. Compare them once, on a call or in person: if they match, they have the right public key.

    Private keys

    Keep secret

    Identity keys sign what you send and open older messages. Save them encrypted with a passphrase, or keep them only in this tab. One-time receiving keys are never saved or backed up.

    Locking clears drafts and decrypted history. Reloading always locks protected keys.

    Back up or restore private keys

    New backups are encrypted with a passphrase you choose. You need that passphrase to restore them. Old unencrypted backups can still be imported.

    Generate a new key pair

    Replace this browser's keys if your private key backup has been compromised.

    • Messages encrypted to your old public key won't decrypt here anymore.
    • Share your new public key with your contacts.
    • Your saved people stay as they are.