Friday, October 15, 2021

Radiator provides IMSI privacy for EAP-SIM, EAP-AKA and EAP-AKA’ authentication

In many high traffic areas such as sports stadiums, shopping venues, or public transport hubs, mobile carriers may partner with the local Wi-Fi providers to improve coverage and user experience: mobile devices can be automatically connected to Wi-Fi instead of congested cellular network. Internationally, Wi-Fi roaming agreements also allow carriers to lower the cellular roaming costs. 

EAP-SIM, EAP-AKA and EAP-AKA’ are SIM-based Wi-Fi authentication methods used to achieve seamless offloading to carrier and partner Wi-Fi, with International Mobile Subscriber Identifier (IMSI) derived from the SIM card acting as a unique identifier for each user. 

On the first ever connection to such a Wi-Fi network, the mobile device communicates its permanent subscriber identity information (IMSI), which is then sent to the home operator for authentication. This identity is sent in the clear. A potential 3rd party adversary installing a Wi-Fi sniffer in the vicinity of such networks can harvest permanent identities and track users. This tracking can also be done by the venue or network owner when connecting to the Wi-Fi network. 

Because of this, mobile operating systems such as iOS15 will show the following warning when joining a Wi-Fi network without IMSI encryption: “your mobile subscriber identity will be exposed”. The similar situation can be seen from the pictures below. 

Privacy warning when authenticating to Wi-Fi network without IMSI encryption


Operators risk decreased user satisfaction for Wi-Fi offloading if transmitting IMSI in the open - it may cause users to feel their privacy is being compromised.

Radiator SIM Pack provides IMSI privacy protection 

The solution is to protect user privacy by implementing IMSI encryption for EAP-SIM, EAP-AKA and EAP-AKA’ authentication. As an operator, you can enable IMSI privacy easily: Radiator 3GPP AAA Server handles both encrypted and clear authentication requests. This means IMSI privacy can be offered to devices supporting it without affecting other users. 

Starting already from revision 2.5, Radiator SIM Pack supports IMSI encryption as specified in 3GPP S3-170116 document “Privacy Protection for EAP-AKA” (zip), and WBA’s IMSI Privacy Protection for Wi-Fi – Technical Specification. The feature is already implemented by some of our operator customers to cover their AAA server encryption. 

The latest release of Radiator SIM Pack is available for new licensees and for licensed customers with valid download access. To find out if Radiator SIM Pack suits your needs, you can contact us at and a member of our sales team will be happy to assist you. 

You can also contact us to renew your support contract and get access to the newest release. A full history of Radiator SIM Pack releases is available on our website.