I have the following conditions:
String which consist of "STRING+key+ID+key" is hashed with md5. I have a knowledge of STRING (10 chars), ID is probabilistic (int 15), key is 15 chars long (a-z A-Z 0-9) and it's same on both occurrences. I can produce multiple hashes but without knowledge of key.
I guess collision is not going to work in this case as STRING is appended at the beginning and ID between keys. Is there actually any other option then brute force.
Produced hash is used as some kind of integrity check so you cannot alter the parameters. Key is hardcoded on the both sides (frontend and backend)