Diffie-Hellman Picture Show: Key Exchange Stories from Commercial VoWiFi Deployments
<|reference_start|>Diffie-Hellman Picture Show: Key Exchange Stories from Commercial VoWiFi Deployments: Voice over Wi-Fi (VoWiFi) uses a series of IPsec tunnels to deliver IP-based telephony from the subscriber's phone (User Equipment, UE) into the Mobile Network Operator's (MNO) core network via an Internet-facing endpoint, the Evolved Packet Data Gateway (ePDG). IPsec tunnels are set up in phases. The first phase negotiates the cryptographic algorithm and parameters and performs a key exchange via the Internet Key Exchange protocol, while the second phase (protected by the above-established encryption) performs the authentication. An insecure key exchange would jeopardize the later stages and the data's security and confidentiality.   In this paper, we analyze the phase 1 settings and implementations as they are found in phones as well as in commercially deployed networks worldwide. On the UE side, we identified a recent 5G baseband chipset from a major manufacturer that allows for fallback to weak, unannounced modes and verified it experimentally. On the MNO side -- among others -- we identified 13 operators (totaling an estimated 140 million subscribers) on three continents that all use the same globally static set of ten private keys, serving them at random. Those not-so-private keys allow the decryption of the shared keys of every VoWiFi user of all those operators. All these operators deployed their core network from one common manufacturer.<|reference_end|>
@article{gegenhuber2024diffie-hellman,
    title={Diffie-Hellman Picture Show: Key Exchange Stories from Commercial VoWiFi
  Deployments},
    author={Gabriel Karl Gegenhuber, Florian Holzbauer, Philipp Frenzel, Edgar
  Weippl, Adrian Dabrowski},
    journal={USENIX Security 2024},
    year={2024},
    archivePrefix={arXiv},
    eprint={2407.19556},
    primaryClass={cs.CR cs.NI}
}