# Signing in and your account

> How privymail.eu protects your account: a password proof that never transmits the password, a second factor without SMS, app passwords and recovery codes.

At privymail.eu, your device proves that it knows the password without sending it to the server. A second factor adds protection for the account, and it does not take a phone number.

## What matters

### Your password stays with you. Even when you sign in.

privymail.eu checks the password with the OPAQUE protocol (RFC 9807): your device computes with the password and only proves that it is correct. The password itself does not reach the server; the server stores a verification record that contains neither the password nor an ordinary hash.

### A second factor. No SMS, no phone number.

The second factor is a one-time code (RFC 6238) generated by an app on your device, or a passkey. There are no SMS codes, and a phone number is not required.

### One password per device. Each revocable on its own.

Mail apps have to store a secret and send it every time they sign in. For this, privymail.eu generates separate app passwords: one per device, each individually revocable, so that your main password is not stored in any mail app.

## How signing in works

1. **Password.** Your device carries out the proof with OPAQUE. The password is not sent in the process.
2. **Second factor.** If one is set up, the service then asks for a one-time code, a passkey or a recovery code.
3. **Session.** Only then is the session created. Changes to the account, such as a new password or a new app password, also require that all factors you have set up were verified shortly beforehand; a stolen session cookie alone is not enough for that.

## Everything at a glance

- **Password proof:** OPAQUE (RFC 9807); the password does not reach the server.
- **Second factor:** voluntary. If one is set up, every sign-in to the account requires it.
- **One-time codes:** RFC 6238, generated by an app on your device. A code that has been accepted does not work a second time.
- **Passkeys:** a second factor, not a replacement for the password.
- **Recovery codes:** you receive them when the account is set up. Each code works once and replaces exactly one factor.
- **App passwords:** for mail, calendar and address book apps. The service generates them, shows them once and, on revocation, also deletes the associated key copy.
- **No SMS, no mandatory phone number:** neither for the account nor for the second factor.
- **Protection against automatically created accounts:** a puzzle that your browser solves (ALTCHA). Puzzle and verification run on our own service; no third-party CAPTCHA service is involved.
- **Sessions:** you see your sessions and end each one individually. For a session, the service stores neither an IP address nor a browser identifier.

## If you forget your password

With a recovery code you set a new password, and your stored mail remains readable. If a second factor is set up, you also need that factor or a second code, because one code replaces exactly one factor. Your mail apps keep working with their app passwords.

Without the password and without a recovery code, the account cannot be restored. We do not know your password and have no master key. A mail app that is already set up keeps reading with its app password; a new one can then no longer be set up. The service therefore asks whether you have saved the codes, and allows a second factor only after that.

## Limits

- **The second factor protects access, not the key.** It decides whether a session is created and whether someone may change the account. It plays no part in the encryption of your mail.
- **App passwords work without a second factor.** A mail app signs in with its app password alone. The protection lies in the service generating it at random and in your being able to revoke each one individually.
- **The password proof protects the password, not the content.** In the default mode, Compatible, the server processes your mail in plain text while you are signed in. For changes to the account, your device also sends a secret that it obtains during the password proof; even then it does not send the password itself.
- **One-time codes can be phished in real time.** A passkey cannot, because it is bound to the address of the genuine site.
- **In the browser, the delivered code counts.** A manipulated server could deliver code that captures the password.

## Questions about signing in

### Do I need a phone number?

No. Neither the account nor the second factor requires a phone number, and there are no SMS codes.

### Is the second factor mandatory?

No. It is voluntary. If one is set up, every sign-in to the account requires it.

### Does a passkey replace the password?

No. A passkey is a second factor. The password remains necessary because access to your mailbox key is derived from it.

### Can you reset my password?

No. We do not know it and have no master key. You set a new password yourself, with a recovery code.

### Does the second factor also protect my mail app?

No. A mail app signs in with its app password, without a second factor. If a device is lost, you revoke its app password.

## Related pages

- [Compatible and Sealed](https://privymail.eu/en/encryption.md): what the server can see, and when.
- [The mailbox](https://privymail.eu/en/mailbox.md): webmail, mail apps and filters.
- [Mail apps and open standards](https://privymail.eu/en/standards.md): signing in from mail apps.
- [Security](https://privymail.eu/en/security.md): principles and encryption.
- [Privacy](https://privymail.eu/en/privacy.md): what data arises and how long it is kept.
- [Roadmap](https://privymail.eu/en/roadmap.md): building blocks and their order.

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- This page as HTML: https://privymail.eu/en/sign-in/
- Deutsche Fassung: https://privymail.eu/sign-in.md