Vodafone is offering an end-to-end encryption for mobile communication based on the phone SIM card. SIM users have to encrypt the data by simply using a PIN and a digital signature, and the same is needed in order to decrypt the communication. The solution uses the widespread S/MIME encryption program for email exchanges, and in the future, encryption via PGP will also be possible. The type of security the company offering would usually require a separate smart card or security token when logging on via a portable computing device.
Source: https://thehackernews.com/2014/03/vodafone-germany-rolls-out-sim-card.html