How to get registration from ICAO 24 bit code? The description of PlanePlotter claims that it can determine the registration letters from the ICAO 24 bit address algorithmically for some countries.

The only thing i got so far is how to get the country. Any clues?

Edit:

After some more research I found some information in the book "Principles of Avionics" by Albert Helfrick: 


  Generally, there is no algorithm giving a one-to-one correspondence
  between ICAO 24 bit addresses and the registration number of the
  aircraft. Some ICAO member states did have an algorithm that would
  translate ICAO 24 bit aircraft addresses to registration numbers but
  ICAO strongly suggested the practice to stop.


Algorithm for swedish registrations: http://www.transportstyrelsen.se/publicdocuments/PDF165.pdf
Apparently (according to these folks) some countries use an algorithm to generate their ICAO (Mode S) 24-bit IDs. For those countries, you can simply reverse the algorithm and get a registration given the Mode S ID.

Others countries allow you to download their registration database, complete with the Mode S identifier (you can get the US registration database here) - it's a simple matter to load this into your own software and map the ICAO/Mode S ID code to a registration number.

As the folks at Gatwick Aviation Society have noted, some countries are tight-lipped about how their codes are assigned (and who they're assigned to), so these lookups are probably not complete.