Hashing is an implementation of encryption that results in an encrypted value that is irreversible. Even if the method used and the key values are known, it is impossible to return to the original value due to rounding and modulus workings. If you want to know how it works, read a book. Oh... wait.

So what can we do with a hash if it can't be reversed? What's the point? Why am I even wasting my time on this hashing rubbish? Well, hashes are used to compare values without showing the unencrypted value at any point. How does that work? Well, the plaintext is hashed and then sent to the database where the correct hashes are stored. If you compromise the database, you only get the hashed value.

So what's the point in my talking about this? Well some people do really, really silly things. If you've ever heard the words, "it's fine, we'll save money by rolling our own encryption," you know what I'm talking about.