Zero-knowledge encryption

In short

• Only you can read

  Submissions are encrypted before they are stored. Decryption happens exclusively in your browser.

• One key for everything

  Set up encryption once in your account. After that all forms are protected – no per-form settings needed.

• Your password unlocks

  The key is protected by your login password. It unlocks automatically when you sign in, so there is no second secret to remember.

• Emails without content

  Notifications only say that something arrived. The content never sits in an inbox or with a mail provider.

How it works

1. 1

   Setup

   Your browser generates a key pair. We receive the public key. The private key is encrypted with a key your browser derives from your password before it is stored with us. You also get a recovery code.

2. 2

   A submission arrives

   When someone submits your form, we briefly check the message for spam and encrypt it with your public key. Only then is it stored. The public key can only lock, never unlock.

3. 3

   You sign in

   At login your browser derives the key from your password and uses it to open your private key. It stays in your browser in a non-extractable form and is discarded after one hour of inactivity and on sign-out.

4. 4

   You read

   Inbox and detail pages only load encrypted data. Your browser decrypts and displays it. Nothing readable ever reaches us in the process.

What we can see – and what we cannot

Encryption covers the content of your forms. We still need some technical details in plain text to detect abuse and spam.

Your password is the key

Notifications without content

Emails for encrypted forms only contain the form name, the time and a link to your account. No fields, no IP address, no reply-to address. That keeps the content out of inboxes, forwards and mail providers’ systems. We also delete copies of our sent emails from our sender mailbox.

Honestly: the limits

Encryption protects a lot, but not everything. So you can judge it properly:

• On receipt, the content is briefly with us

  Your forms are plain HTML on your website. The message therefore reaches us unencrypted (but via HTTPS) and is processed in memory for a moment for spam protection. Plain text never ends up in the database, logs or backups.

• You trust the code we deliver

  As with any web application, encryption runs in code your browser loads from us, and your password reaches us at login as before. This does not fully protect against a compromised server. It does reliably protect against everything that only gets at stored data: database leaks, backups, hosting providers and our staff.

• As strong as your password

  Anyone who knows your password can read your submissions. Use a long, unique password, ideally from a password manager. Also turn on two-factor authentication – then a stolen password alone is not enough to sign in.

• Older submissions stay as they are

  Everything received after setup is encrypted. Submissions from before stay unencrypted until you delete them.

• Technical details stay visible

  We still need IP address, time and origin page to detect abuse. The spam metrics contain no text.

Technical details

For those who want to know exactly. We only use established standard algorithms and the cryptography built into the browser (WebCrypto) – nothing home-grown.

Key pair

RSA-OAEP with 4096 bits and SHA-256, generated in the browser

Content

AES-256-GCM with a separate random key per submission, which is encrypted with your public key

Password

PBKDF2-SHA-256 with 600,000 iterations; the result wraps the private key using AES-256-GCM

Stored with us

Public key, the wrapped private key and the encrypted submissions – none of it can be opened without your password or recovery code

In your browser

The unlocked private key is kept as a non-extractable key object in IndexedDB, for at most one hour of inactivity

Frequently asked questions