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1xEV-DO Roamer Authentication

1xEV-DO Roamer Authentication. Sarvar Patel, Simon Mizikovsky, Zhibi Wang. AAA. AAA. zhibiwang: User Authentication uses CHAP?. 1xEV-DO Security Architecture. RNC. Corp. FW. A10/A11. 1xEV-DO BTS. PDSN. Internet. Session Key Agreement. A12. A13. Device Authentication (Inner CHAP).

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1xEV-DO Roamer Authentication

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  1. 1xEV-DO Roamer Authentication Sarvar Patel, Simon Mizikovsky, Zhibi Wang

  2. AAA AAA zhibiwang: User Authentication uses CHAP? 1xEV-DO Security Architecture RNC Corp. FW A10/A11 1xEV-DO BTS PDSN Internet Session Key Agreement A12 A13 Device Authentication (Inner CHAP) User Authentication (Outer CHAP) Session Authentication (Integrity MAC) IPSec RAN Encryption (AES)

  3. Current status • Operator A can performs (NULL, MN-AAA) (RAN level, PDSN level) authentication • Operator B can performs (A12 CHAP, NULL) • A roaming solution: • Operator A set RAN-AAA CHAP password to be the same as MN-AAA key so that Operator B can perform a RAN level CHAP when Operator A’s user roams into Operator B network. • Operator A Analyze the realm at the A12 level, and if it is an Operator A user, RAN level CHAP will be bypassed. If Operator B user, RAN level CHAP will be performed against AN-AAA in Operator B’s network.

  4. Potential attack • Since NAI/Authentication at the RAN level and the PDSN level are independent and can be different • An attacker can • Use an Operator A NAI at the RAN level Operator A bypasses RAN level CHAP (it thinks the user is an Operator A customer at this level) • Use an Operator B NAI at the PDSN level Operator A bypasses PDSN level authentication (it thinks the user is an Operator B customer at this level)

  5. A Possible Solution • Operator A Performs (A12 CHAP, Mobile IP Authentication) for its users and (A12 CHAP, NULL) for Operator B roamers • An attacker can still avoids usage billing by • Subscribe Operator A service and use Operator A NAI and CHAP password to gain RAN level access, at the PDSN level the attacker uses Operator B NAI, this causes Operator A to bypass PDSN level authentication • Since Operator A does billing at the PDSN level the attackers extra usage would not be accounted for

  6. Solution • RNC report to PDSN the NAI that is used by the AT at the system access • PDSN verify the NAIs at two different level, if they are mismatch, terminate the session • Requires A11 interface change to transport the ID of the HRPD AT, specifically the NAI, to the PDSN

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