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IGTK Switch Announcement

IGTK Switch Announcement. Date: 2018-05-06. Authors:. Abstract. This submission identifies some issues with IGTK update and provides a solution to address the issues. The submission also provides a solution to address LB232 CID 1067. Agenda. Problem Statement Proposed Solutions

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IGTK Switch Announcement

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  1. IGTK Switch Announcement Date: 2018-05-06 Authors: Emily Qi, et al

  2. Abstract This submission identifies some issues with IGTK update and provides a solution to address the issues. The submission also provides a solution to address LB232 CID 1067 Emily Qi, et al

  3. Agenda • Problem Statement • Proposed Solutions • Solution Details • An Example Emily Qi, et al

  4. Background • Since both GTK and IGTK are shared by all associated STAs, the AP typically updates their value on a regular basis as well as when an STA disassociates from AP. • This is achieved by • First, updating all associated STAs, one by one via unicast frame • Once the new non-active GTK and IGTK are set in all STAs, the AP will start using the new Key IDs as the ‘active’ GTK and IGTK for the following group-addressed Data frame and Management frames protection, respectively. • Which means that there is a delay between the time the new keys were set by AP in the STA and the time where AP actually starts using the new keys instead of the old ones. Emily Qi, et al

  5. Problem Statements • For group addressed data frame, the used GTK Key ID is indicated in the beginning of the frame (e.g. the Key ID field in the CCMP header), so that the STA knows quiet early which GTK to use. • However, for group addressed management frame, the used IGTK Key ID is indicated in the MMIE (Management MIC Information Element), which is located at the end of the Protected Group addressed Management Frame. • The receiving STA won't be able to start computing MIC value until reaching the end of management frame body. Emily Qi, et al

  6. Proposed Solution • Following GTK/IGTK rekeying, AP notifies all associated STAs on when it will start using the new IGTK prior to switch to the new IGTK when AP is still using the old IGTK key • The notification can be included in the Beacon frame. Emily Qi, et al

  7. Solution Details • Include a new IE “IGTK Switch Announcement IE” in the Beacon frame: • New Key ID • The New Key ID field identifies the new IGTK to be used to compute the MIC. The IGTK Key ID is either 4 or 5, as defined in 9.4.2.54. • IGTK Switch Count • the IGTK Switch Count field is set to the number of TBTTs until the STA starts to use the new IGTK. • A value of 1 indicates that the switch occurs immediately after the next TBTT. The new IGTK will be used immediately after the next Beacon transmission. Emily Qi, et al

  8. Example of using IGTK Switch Announcement Emily Qi, et al

  9. Backup Emily Qi, et al

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