Help Cipher

A private message. Any chat.

Write here. Paste the locked link in your usual chat.

Help & details

  1. Swap IDs once

    Share your Cipher ID link and open theirs to add them. Then check your safety emoji together once.

  2. Write, then lock & copy

    Press Ctrl ↵Tap Lock & copy, then paste the copied link into any chat, email or post. More options are under More.

  3. Tap to read

    Open their link in the browser where your Cipher ID is saved. Locked text still works: paste it here to read.

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

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

About your Cipher ID
Made for you
Your browser creates it the first time you visit. There's nothing to sign up for.
Safe to share
It works like a mailing address: anyone with it can send you private messages, but nobody can use it to read them. The part that opens your messages never leaves this device.
Saved in this browser
Clearing your browsing data deletes it. To keep a backup, or to use it on another device, copy a transfer code from My ID.
Security details
Encryption
AES-256-GCM, with a fresh key for every message (HKDF-SHA-256, random 128-bit salt).
Quantum-safe
Every message key combines X25519 with ML-KEM-768, the NIST post-quantum standard. Reading a message would mean breaking both, so messages recorded today stay private even from future quantum computers.
Sender
A message that opens is proven to come from the person shown.
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 own WebCrypto, plus one pinned, checked copy of the noble ML-KEM library. Nothing else.
What it can't hide
  • Your chat app still sees that you sent something, when, to whom, and roughly how long it was.
  • The part of your ID that opens messages is saved in this browser. If someone copies it, they can open earlier messages sent to you that they've kept.
  • 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 Cipher and press Lock & 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 Cipher to read it.

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

Your Cipher ID

Send your ID link so someone can write to you.

Paste it in your usual chat.

Check safety emoji

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

    More options …
    Use your ID on another device, or back it up

    A transfer code puts this same ID on a second phone or computer, so messages to you open on both. Kept somewhere safe, it's also a backup if this browser's data is ever cleared. Treat it like a house key: anyone who has it can open messages sent to you.

    Then, on the other device, open Cipher, go to My ID, open this section and paste the code below.

    Start over with a new ID

    Makes a brand-new Cipher ID on this device. Do this if you think someone got hold of your transfer code.

    • Messages sent to your old ID won't open here anymore.
    • Send your new ID to your people so they can message you again.
    • Your saved people stay as they are.