About Sha512 Decrypt :
Sha512 is a function of cryptographic algorithm Sha2, which is an evolution of famous Sha1. Sha512 is very close to its "brother" Sha256 except that it used 1024 bits "blocks", and accept as input 2^128 bits maximum. Sha512 also has others algorithmic modifications in comparison with Sha256. This cryptographic function is part of the U.S Federal Information Processing Standard.
On this website you're able to encrypt (hash would be the correct way to say it) any string you want by entering it in the textarea (we do NOT store user's inputs so don't worry to try for your actual password). This will provide you with a 512 bits hash (so 128 hexadecimal characters).
As Sha512 is a hashing algorithm you have no way to "reverse" it with only the hash. Which means you're unable to find back the original plaintext by looking only at the hash (or condensate) it produces. The only way that you can use to decrypt Sha512 hashes (or unhash it), is to compare the hash with a database (such as rainbow tables or hash tables). This is what we provide on this website, here we have a 2 billion database containing passwords and associated hashes.
If you enter a sha512 hash in the textarea, the server will look if it has it stored in the flat database, if so it will return you the plaintext. If we don't have it stored, we store every unfound hash in a file which is often passed through hashcat to bruteforce everything we can, so you may come back after a few weeks and discover that your hash is now in our database. Now if you want to store passwords on a database using Sha512, you should use a salt even if Sha-512 is less flawed than md5/sha1 due to its length. As I said, tools like hashcat can bruteforce dozens of billion passwords per second, Sha512 is optimized for 64-bits CPU so it's actually fast to crack. If you add a salt, it will make harder for hackers, though not impossible with powerful computers. The good way to encrypt passwords now is with slow hashes algorithm such as Bcrypt for instance. This is nearly impossible to crack if you use a passphrase (with the nowadays computer though, quantic CPU are on their way to destroy all this).