So far, most users have probably only come into contact with the topic of encryption with cell phone messengers – many chat applications have end-to-end encryption, some apps even have other special features that protect private data. But telephone calls over the fixed network can also be encrypted. Two things are enough to block out unwanted eavesdroppers: an up-to-date DSL FritzBox and a connection with a provider that supports encryption. Here you can find out which basic requirements must be met in detail, where the encryption ends and how to activate the protection against eavesdropping.
Encryption: requirements and limitations
In order to use the encryption of the AVM router, you need a DSL FritzBox with the operating system version FritzOS 7.20 or higher. You also need a connection with Voice-over-IP (VoIP) from a provider that offers secure transmission; these include, for example, Deutsche Telekom, Easybell and dus.net. Unlike a secure mobile phone messenger, the call data is not end-to-end encrypted, but only on the transport route to the provider’s server. Whether the data is then transmitted encrypted from there depends on the settings that the server negotiates with the next partner. The FritzBox uses the SIP-over-TLS protocols with SDES-SRTP for encryption.
Newer DSL FritzBoxes such as the 7530 AX support encryption.
FritzBox: Set up encryption
To activate encrypted telephony, connect to your FritzBox and follow these steps:
- Call up the FritzBox menu by entering http://fritz.box/ in the address bar of your browser.
- Log in with the device password.
- Activate the extended view via the three dots at the top right.
- Choose from the menu on the left telephony and Own phone numbers.
- Click the pencil icon next to the phone number whose calls you want to encrypt.
- click on More settings and set the hook Activate encrypted telephony.
- Finally, confirm by clicking on OK.
Under telephony, Own phone numbers and voice transmission the FritzBox should now display the addition “encrypted” for calls made. Note: The menu item for encryption is only visible if your provider offers the function.