Can’t the steps be reversed one by one to get back the original?
In: Mathematics
One of the methods used in hashing is modulo arithmetic, which means taking the remainder of a division. As an example, most people would say 5 divided by 2 is 2.5, but with modulo, you would say 2 goes into 5 twice with 1 remainder. However, there are multiple ways to get 1 remainder. You could also have 5 modulo 4, or 7 modulo 2.
If you consider modulo as a little ingredient and your hash is a recipe made of 100 ingredients you can see how it’s easy to turn plaintext into a hash but hard to turn a hash into plaintext.
Even insecure hashes like MD5 can’t be reversed in the traditional sense; the best you can hope for is a collision, which means that two inputs produce the same output (which isn’t supposed to happen; in practice this would mean you could log into an account with two different passwords.)
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