A hash function or hashing algorithm converts any input data into a fixed-length hexadecimal value. It does not require a key. Regardless of the size or type of the input, a given algorithm produces output of a fixed length.

This fixed-length sequence of digits is called the hash value or message digest. Even a small change in the input will produce a completely different hash value. Because of this, a hash value is considered similar to a digital fingerprint of the data. It is impossible to reverse the hash value to recover the original data. For this reason, it is also called one-way encryption.