hash & salt MACs before store them in RAM

[cyberman54]

• scramble MACs before storing them in RAM, to improve privacy
• add hash & salt function for this purpose

[cyberman54]

Solution idea:

First, the captured MAC address (previously possibly vendor-filtered) is truncated, then a SALT value is appended, a hash function is applied to it, and the result is truncated to make it look like a regular MAC address. The result is an identifier. Temporarily in RAM only the identifiers are kept. These alone form the counting basis.

The SALT value is regenerated at device reset or at certain (minimum) intervals. Thus, the identifiers after device reset or expiration of the interval are different from those previously detected. A recognition of devices / persons is thus without further fingerprinting (which is not part of the code) not possible, even if the identifier data was stored somewhere for a long period of time.

The SALT value must be a random number that is not persistent and is stored only in volatile RAM.

Using a separately running RTos task "scrambling_task", which is working continously on the MACs set:

forever do {

• read next input MAC from set
• salt+hash MAC
• store back to set, replacing original MAC
  }

This way the MAC set contains only identifiers, which are counted.

[trlafleur]

This might be of help...

forum.arduino.cc/index.php?topic=394998.0

[cyberman54]

implemented (v1.2.6).