Secret community forming based on zero-knowledge proof (IOT)
How big is the secret key that defines a community?

If it is trivial, say a number between 1-100, then an attacker can easily calculate 100.000 hashes to know in which community each user is.

If the secret s is long, say 64 bytes, then I don't see the usefulness to generate 1000 hashes for each option. Then it would be best to just send your hash H(s+n), with a random nonce n you used (as knowing the nonce and the hash would not help anyone else to know the secret).