I've read some Q&A about combining OTP with hash on this site, but I still wonder why some answers said that using hash for OTP key is not strong enough to resist brute force attack?
Assuming that the key is never reused and the adversary has unlimited computational resources so that the adversary can try all keys easily. Is the adversary able to find out which one is correct from all of the plaintexts after getting all possible plaintexts?
For example, if the adversary gets "Give me 100 dollars.", then he might get "Give me 200 dollars." too. If he can't filter out the wrong plaintext, how does he know the correct key and crack it?
I know the amount of possible plaintext depends on the amount of possible hash value, but if the adversary gets at least two possible plaintexts and has no any method to distinguish the right one from them, will this cipher encrypted by hash key have any chance to be cracked by brute force attack? If no, then are there any flaws in this encryption technique? (Ignore the message authentication problem)