Improving MAC Header Protection in IEEE 802.11-23/1888r0 Proposal
Enhance the reliability and security of MAC headers in IEEE 802.11-23/1888r0 by implementing a comprehensive protection scheme. Explore the factors influencing header protection, parameters for MIC generation, and considerations for temporal key usage. Address the need for safeguarding critical fields in MAC headers to boost efficiency and minimize vulnerabilities.
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November 2023 doc.: IEEE 802.11-23/1888r0 MAC header protection follow-up Date: 2023-11-02 Name Affiliation Address Phone Email Abhishek Patil appatil@qti.qualcomm.com Duncan Ho Jouni Malinen Qualcomm Inc. Alfred Asterjadhi George Cherian Gaurang Naik Submission Abhishek P (Qualcomm), et. al., Slide 1
November 2023 doc.: IEEE 802.11-23/1888r0 Background UHR is focused on improving reliability, reducing latencies and lowering power consumption at devices. In order to achieve these goals, UHR will rely on signaling information via the MAC header fields (such as A-Control) or via Control frames (e.g., Trigger etc). However, Control frames and several fields in the MAC header are not protected. Several contributions have highlighted the need for protecting these fields and frames to help UHR meet its objectives [1, 2, 3, 4] This contribution provides additional details on MAC header protection and considerations for selecting the security parameters to enable this protection. Submission Slide 2 Abhishek P (Qualcomm), et. al.,
November 2023 doc.: IEEE 802.11-23/1888r0 Factors to consider (recap) The header protection scheme needs to account for field values getting updated when an MPDU is retried. Such as Retry bit, PM bit, A-Control field etc In addition, the scheme must not require re-encryption of the payload of an MPDU during a retry Consequently, MAC header protection cannot be combined with MPDU encryption. In other words, the two need to be separate processes and only the header protection step is performed when an MPDU is retried. Submission Slide 3 Abhishek P (Qualcomm), et. al.,
November 2023 doc.: IEEE 802.11-23/1888r0 Overview of the proposal Protection is provided via integrity check A MIC is generated based on (subset of) MAC header fields. Since the contents of the header fields can change when an MPDU is retried, a fresh MIC is generated (only) for the header fields each time an MPDU is retried Note, the payload of the MPDU is not re-encrypted Submission Slide 4 Abhishek P (Qualcomm), et. al.,
November 2023 doc.: IEEE 802.11-23/1888r0 Parameters needed for MIC generation MIC generation will require the following parameters: A temporal key (TK`) A packet number (PN`) Address 2 (A2) field which carries the transmitter MAC address Fields of the MAC header that need protection A2||PN` is used to generate a Nonce Next, we examine additional considerations for TK` and PN` Submission Slide 5 Abhishek P (Qualcomm), et. al.,
November 2023 Proposal for temporal key (TK`) for MIC computation doc.: IEEE 802.11-23/1888r0 From security point of view, using the same key in two different algorithms is a bad practice As it can make related key attacks possible. Therefore, TK` cannot be the same as TK (which is used for encrypting the MPDU payload) Therefore, a separate TK` is generated during association. TK` will be identified with the corresponding value in the Key ID field The separate TK` can also be used for (individually addressed) Control frame protection Submission Slide 6 Abhishek P (Qualcomm), et. al.,
November 2023 Proposal for packet number (PN`) for MIC computation doc.: IEEE 802.11-23/1888r0 The PN` provides protection against replay attacks Same functionality as PN used during the payload encryption However, the usage of PN` differs from PN in the following aspects: The PN value remains the same when an encrypted MPDU is retransmitted. In contrast, a new PN` value is required each time an MPDU is (re)transmitted a new MIC is computed for each (re)transmission. Packet number required for (individually addressed) Control frame protection can also be drawn from the PN` space Submission Slide 7 Abhishek P (Qualcomm), et. al.,
November 2023 doc.: IEEE 802.11-23/1888r0 In summary This contribution proposes to protect fields in the MAC header via integrity check A new MIC is generated for the header fields each time an MPDU is (re)transmitted A separate TK` is generated during association for header MIC generation Same TK` can be used for protecting Control frames Packet Number (PN`) used for generating the MIC (for header field or Control frame protection) is drawn from a different space than that used for MPDU encryption Submission Slide 8 Abhishek P (Qualcomm), et. al.,
November 2023 doc.: IEEE 802.11-23/1888r0 References [1] 11-23/286: Trigger frame protection [Po-Kai Huang et al. (Intel)] [2] 11-23/352: Enhanced security discussion [Liwen Chu et al. (NXP)] [3] 11-23/356: MAC Header Protection [Abhishek Patil et al. (Qualcomm)] [4] 11-23/1102: Security Enhancement follow up [Liwen Chu et al. (NXP)] Submission Slide 9 Abhishek P (Qualcomm), et. al.,
November 2023 doc.: IEEE 802.11-23/1888r0 SP #1 Do you support to define a mechanism in TGbn that protects the MAC header for individually addressed Data and Management frames? Submission Slide 10 Abhishek P (Qualcomm), et. al.,
