I'm reading about 802.11, from IEEE's PDF, from page 1191, and in particularly I'm reading about TKIP. To decrypt and encrypt, you use a TSC (TKIP Sequence Counter) as you can see in these images:

Figure 11-5 — TKIP encapsulation block diagram

Figure 11-6 — TKIP encapsulation block diagram

How, and from what, is the TSC calculated?

  • Do you have more source where i can also study TKIP? On internet it has very less information about its working. – defalt Jul 9 '17 at 14:33
  • TKIP is a relic of a past age and is no longer relevant to correctly configured modern 802.11 networks. Since 802.11n, HT (and now VHT with 802.11ac) data rates must be enabled if TKIP is in use. This negates many of the advantages of newer additions to the standard. – YLearn May 1 '19 at 21:50

TSC is just a counter used for anti-replay mechanism and it increases by 1 for every MPDU. Thus, its value depends on the sequence of the MPDU. I am not quite certain about its initial value but i suppose it depends on the implementation as usually.

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TSC is a 48-bit counter. It is initialised to 1 every time the TKIP temporal key is initialised or refreshed.

Each MPDU must be sent with a unique/different TSC, to protect against replay attacks. It is incremented by 1 for each subsequent use.

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