#What is a Hash?

A hash, also referred to as a hash value or a message digest, is a number generated from a string of text. It is a one-way cryptographic function that is used to summarize the data into a fixed length code. Put simply, the hash code is a value that resembles the original message, but it cannot be converted back into the original message. Moreover, hashes provide a way of verifying digital signatures and ensure the authenticity of digital documents.

In plain terms, a hash is a value that can provide a certain degree of certainty that two pieces of data, such as documents and files, match. When two pieces of data have the same hash, then one can be sure that the two pieces are identical, regardless of any external identifiers. If two pieces of data have different hashes, then one knows that the two pieces of data differ in some way, even if only by a few characters.

#How Does a Hash Work?

A hash is created when a mathematical algorithm is applied to a string of data. These functions usually generates a fixed-length string for a given data set. A common example is a Message Digest 5, also known as MD5, which creates a 128-bit hash of the data.

It is important to note that a hash is not the same as encryption; hashes are not reversible and cannot be deciphered back into the original string. What data is originally input will always be the same output the hash value, meaning that if any data is changed in the input, a completely different hash will be produced. This means that the output value is truly unique and that it functions as an identifier for the data set and is used to check the integrity of data.

#Uses of Hashes

Say, for example, a file has been transferred from one computer to another. How can we be sure that the file did not undergo any modifications or data corruption during transfer? The answer is by hashing.

When transferring a file from one computer to another, a hash of the source can be taken and compared against the hash of the destination file upon completion to verify their similarity. If the hashes of the two files are identical, then one can be certain that the file has not altered during transfer.

Hashes are also commonly used in password databases, where a hash code of each user’s password is stored instead of the plain-text information. This ensures that the passwords cannot be accessed in the event of a security breach.

Hashes have become an integral part of today’s computing environment, and are becoming increasingly important as we continue to rely more heavily on digital documents and networks.