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Dan brought up a couple of good observations after my presentation on the IRM/ID scheme. Dan was concerned that in the case of a stadium there could be 10’s of thousands of devices which would put a big burden on the AP/Network in calculating the
hash and finding the key (IRMK). This would be true but on reflection I now realize that this is not a Use Case that TGbh has considered and also I doubt if it would be. In this case I suspect that the APs would not indicate support for IRM and hence the
STAs would not use it. The ID Query might be used, not sure. Still it’s a good point and I do want to make sure the effort is kept a low as possible.
The idea of the IRMK Check was to reduce the work by the AP. The IRMK Check at the moment uses a random start bit. Dan expressed that it was still a lot of work for an AP to go through all the IRMKs and perform the 16/8
bit EXOR at the point that the STA is associating. There was a suggestion that a fixed offset could be used and on reflection I think this is a practical solution. When the STA associates, it provides a new key (IRMK) and if we had a fixed offset, the AP
could quickly calculate the 8 bit Check and store it with the key, i.e., it stores the 9 octet key and 1 octet check, 10 octets per STA. Then when the STA indicates the Check, the AP has a simple job to find those keys that match the check (reducing the list
by a factor of 256). As an aside to this, I did at one time consider using a CRC-8 as the check. I am not an expert on this but I felt that that was more work – I may be wrong, so
if anyone feels that would be better please let me know. Thanks Graham To unsubscribe from the STDS-802-11-TGBH list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-11-TGBH&A=1 |