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    Note that this is not referred to as "decryption" because you don't get back the original string - just another string that hashes to the same value. Unlike encryption, hashes can't be reversed Commented Aug 11, 2020 at 21:36
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    Does this answer your question? Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it? Commented Aug 12, 2020 at 9:14
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    Note that for weaker password hashing algorithms it's a frequent occurrence that a password hash cracking tool bruteforces a hash and finds a password which was not the original password, but since it has the same hash it will be accepted. However with stronger/longer hashes this is not seen as you cannot run a exhaustive search and the probability of bruteforcing a second pre-image is very low. Commented Aug 12, 2020 at 9:36
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    Yes, you can do that. Have you tried? If you try, you might find some weird obstacles in your way. Now consider that nobody has been able to find a way around those obstacles yet. They did for older hash functions like MD5, which is why we don't use old hash functions any more. Commented Aug 12, 2020 at 14:08
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    Wouldn't the answer (yes, which is why you need to pick a good algorithm) be on the first page of any tutorial on hashing? Commented Aug 13, 2020 at 1:19