Why do you not believe what you have read?
Cryptographic hash functions can not be reversed.
Thought experiment: You have 200 bytes you pass to SHA512, out come 64 bytes. Something has been lost. How do you regain what is lost?
In a similar manner if you have an integer, say 123, and mod by 10 the result would be 3. Now reverse that–oh it could have been and of 3, 13, 23, 33, 123, 9343453, *3.
