How does the SHA-512 decoder on the following page work? http://md5hashing.net/hashing/sha512#main
Hash values supposed to be unable to reverse. Is this page fake?
The site does only provide a rainbow table (a lookup of the possible text from the hash).
So it is simple a database with all hashes saved (so far because a user has entered the text for the searched hash before).
If you enter a hash value (e.g. 3d24c2171cac6da8435ff671c8408189688101be2581d20870a2cb508870048afec15eecd7ed8c406d4d86da746c8caf66db75d9060543dd5d29faca95819707) that was not hashed by them then the following error message appears:
Results not found in DB or your request exceed execution time. Anyways - please try again later.
Also they clearly state that they only provide a rainbow table:
"Decryption of hash (unsolted) is impossible, but we offer reverse decryption via our database (~245M records, and counting)."
Simple Answer: Rainbow Tables
This site save every Hashvalue you Entered to Hash it. So it could reverse search it in his own database.