RESEARCHERS HAVE UNCOVERED flaws in the Authentication and Key Agreement (AKA) protocol that could render 5G networks vulnerable to eavesdropping and man-in-the-middle attacks.
The AKA protocols are also used in 3G and 4G networks today. 5G AKA incorporates a strengthened authentication process intended to combat the interception of communications via the use of IMSI catchers.
Furthermore, while G3PP, the global organisation behind mobile communications standards, has been informed about the security flaws, it will take some time before the protocols are patched.
In the meantime, first generation 5G networks are likely to be vulnerable to the security flaw highlighted by the researchers.
The 5G AKA protocols authenticate a device equipped with a standard USIM card against an account to enable access to a mobile network. "In a nutshell, AKA is a challenge-response protocol mainly based on symmetric cryptography and a sequence number (SQN) to verify freshness of challenges, preventing replay attacks," explain the researchers.
5G AKA had been designed to protect networks against the same fake base station attacks that 3G and 4G networks proved to be vulnerable to, compromising security and privacy.
"We found a new logical vulnerability in the specifications of all aforementioned variants of AKA: the protection mechanism of the SQN can be defeated under specific replay attacks due to its use of Exclusive-OR (XOR) and a lack of randomness," write the researchers.
They add that this flaw can be used to "break the confidentiality of SQN, thus defeating the purpose of a dedicated protection mechanism and breaking an explicit privacy requirement".
Furthermore, the researchers also put together a low-cost proof of concept to demonstrate the feasibility of real-world attacks against the AKA protocols.
The security flaw was discovered last year by the researchers from the Technical University of Berlin, ETH Zurich and SINTEF Digital in Norway. The main suppliers of 5G mobile networking equipment - Ericsson, Nokia and Huawei - were all informed, as were the carriers Deutsche Telekom and Vodafone in the UK.
"Our findings were acknowledged by the 3GPP and GSMA and remedial actions are underway to improve the protocol for next generations… while 5G AKA will suffer from our attack in the first deployment of 5G," they warn. "We are still hopeful that 5G AKA could be fixed before the deployment of the second phase". µ
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