Hashing is a one-way mathematical function. It requires little computing power to convert a plaintext string to its hash value (hashes). However, it will require a huge amount of computing power to retrieve the original string from the hash value (it's almost impossible). Therefore, we call it a one-way function:
Figure 3.13: Workings of the hash function
With this property, a hash function is perfect for a hashing password. We will hash the user's password into hashes before we save it to the database so that it is unrecognizable and irreversible. And next time, when the user logs in, what the platform does is to convert the input the password to its hash value, and then compare that with the hash value stored in the database. That way, we can perform a password comparison without leaking the sensitive password information to others.
Exercise 22: Implement the User Registration Feature and Hash the User's Password