Detect / prevent the use of range extenders?

[JB21]

Is there any way to detect / prevent the use of range extenders?

When using a central & server with low TX power, the range is say 10m. Now an attacker can use a relay where central & client unknowingly connect to and thus increasing the range. For encryption we can only use Just Works, and the relay can also use that. So that's no help.

Is there any way to detect the longer travelling time of messages? If the relay uses short connection intervals then the added delay may just be too small to be detected?

Any ideas?

[Petter Myhre]

I see. It is difficult to protect against such attacks when no user action is required to "open" the door, just proximity.

The minimum connection interval is 7.5 ms, so if a central does a read it would typically receive a response in a bit more than 7.5 ms, but by spec it can be up to 30 seconds before the transaction times out.