That would seem more logical, are VINs unique worldwide? If not how could you use a supercharger in France for example?
Yes VIN's are globally unique
Digits 1–3, World Manufacturer Identifier (WMI): 5YJ = Tesla
Digit 4, Line/Series: S = Model S
Digit 5, Body Type: A = 5 Door Hatchback LHD, B = RHD
Digit 6, Restraint System:
Digit 7, Charger Type (earlier VINs) or Battery Type (later VINs):
Digit 8, Motor/Drive Unit & Battery Type (earlier VINs) or Motor/Drive Unit (newer VINs):
Digit 9, Check Digit: Variable
Digit 10, Model Year:
Digit 11, Manufacture Location:
Digit 12, Production Series:
Digits 13–17, Production Sequence Number
- but again no authentication needed as it is the CAN protocol that turns the Supercharger on.