I have seen a lot of articles and research papers about breaking the Keeloq algorithm. My understanding is that the hardest part is getting the 64 bit manufacturer key. Some methods use crypto-analysis and some use power analysis to get the key. Once the manufacturer - and other parameters - have been obtained it is trivial to create an arbitrary number of remotes to your garage, car, or whatever.
I have two questions about that :
Do manufacturers in general (cars or garages) still use Keeloq as their algorithm after these attacks and vulnerabilities have been exposed? Or are other algorithms used, for instance manufacturer specific ones?
If the manufacturer key is not public and is stored in the receiver, how do some Chinese manufacturers sell some car remotes (specifically some older models)? Do the original manufacturers publish their keys after the car is out of production? Do the keys get leaked?
Because honestly I don't think Chinese mass production companies would go through all the trouble of breaking the cipher to get the key.