How is synchronization of counter values achieved in the HOTP protocol?
As I understand it, the server increments its counter value only if a match (of the OTP value) is found. What happens at client side?
Suppose server verifies 50 successful attempts from client which implies counter value at server is 50. What if a fresh request comes from a different client with counter value 0? The server could only check for counter values 50,51,52 if window size is 3,or 50-100 if window size is 50. In both the cases there will be no match as client side counter value is 0.