What is Hashing: Complete Explanation

A hash function is a method for converting strings of different lengths into fixed-length strings called hash values or digest. It can be used to scramble passwords into strings of authorized characters. It can encrypt communications between web servers and browsers. It can be used to hide sensitive data from prying eyes such as passwords, payment details, and web analytics. It can even be used to locate identical or similar data sets with search functions.

The function was given its name after the cooking method. “To hash” means to chop or scramble something like hashed browns. The function does the same to data. As described above, there are multiple reasons for data to be hashed.

Making hashed browns requires a grate or cutting utensil to pull the potato apart before frying. In a similar manner, hashing data also requires a specific utensil or tool. The difference is that it is a software tool. Specifically, there are different types of hashing formulas that act as the grating/cutting method for data.


  • MD2
  • Tiger
  • CRC32
  • Adler32
  • SHA-1
  • RipeMD128
  • MD5
  • SHA-512

Hash Function Qualities

Aside from the different formulas that can be used to hash out data, there are three specific qualities that all hash functions must be up to standards. The next section details these three specific qualities and the importance of each one as a useful mathematical function for cryptography and blockchain data structure.

Unique Hash Value

No two strings should output the same hash value. In simpler terms, every input string must create a unique output string value. This allows for collision-free performance and better security for encryption purposes.

If you’re unfamiliar with software collisions, it is when a namespace or value is duplicated or similar enough that software functions interact with the wrong target value or reference by mistake. While it may seem like a silly problem, the occurrence of duplicate IDs throughout software coding has been a long-time problem.

Aside from avoiding programming and reference errors, unique values are also important for encryption.


To be a useful function, it must perform quickly. With the amount of access made to hash tables, the function must be quick enough not to bog down overall performance.


Arguably the most important quality is that the security of hash values is maintained. That means that once the value has been generated, it must be impossible to convert it back. The hash value is used to reference the hash table for information access. If the value can be converted back into the original string of data, the information security is at risk. What use is keeping passwords encrypted if they can be easily undone?

Hashing in Cryptography

The hash function is incredibly important in cryptography. In fact, a cryptographic hash function is used to authenticate the veracity of a piece of data. The formulas in the list above are also called cryptographic hash functions.

These functions are used to make sure that data or files being accessed online are safe and verifiable. They are also used to keep usernames and passwords organized in a useable, but secure manner.

Hashing: An Exact Definition

Hashing refers to the use of a hash function or algorithm to map object data to a representative integer value or fingerprint. Hash functions, also called cryptographic hash functions, convert strings of different lengths into fixed-length strings known as hash values. The functions are used across the computer science industry to:

  • Encrypt communication between servers and browsers as well as generate session IDs for data caching and online applications
  • Protect sensitive data such as web analytics, usernames, passwords, and payment information
  • Add digital signatures to emails
  • Locate identical or similar data sets through search/lookup functions

Successful and useful hashing functions have three distinct traits:

  • Hash values can not be reversed to obtain the input string.
  • Hash values are unique to the input strings meaning no two strings should create the same hash value.
  • Hash functions need to be incredibly fast to ensure smooth operation performance.

To put it as simply as possible, it is designed as a method to efficiently find or store data in a collection of data.

Hash Values

Hash values are the output created by hash functions. Every value generated by the same hash function formula will be the same length regardless of the length of the input string. These values are used as a type of unique ID to allow for encrypted verification to allow a user access to web servers. These values can then be used by the servers to checksum field inputs and quickly find information in a stored data structure using the value as an identifier.

Hash functions are used to add signatures to emails.

How Does Hashing Work?

The simplest way to describe how it works is to think of it in physical terms. An input string, which is text, typically used to fill out forms like usernames and passwords, is chopped into pieces and reorganized according to the rules outlined by specific hash block algorithms. Any length of string input can be taken and then represented as a specific length string known as a hash value.

The original input and the hash value created are stored in a hash table to be accessed for reference. For example, if you sign into a website with a username and password, the form data is put through the algorithm the site uses for hashing. The username and password are then converted into a unique hash value. Instead of transmitting the form data, the hash value is sent to the server. The server then checks the hash value through the hash table to verify that the input string was correct.

The value of this is that if a hash value is intercepted by a third party, they can’t convert the hash value back into the original string which in turn protects your sensitive information.

How Do You Create Hashing?

Hash functions can be created by using specific mathematical algorithms to convert input strings into a set length value. They can be created by choosing a predetermined hash algorithm or creating your own. It’s often recommended to use the tried and true methods already available. For learning purposes, you may wish to create your own to form a better understanding of how they work.

Here’s a list of the different algorithms used:

  • SHA-1
  • SHA-512
  • MD2
  • MD5
  • Tiger
  • CRC32
  • Adler32
  • RipeMD128

Once you decide on how to create your hash values, you’ll need to organize a hash table data structure to make use of it. The hash table will need to have three useable functions: insert(key, value), get(key), and delete(key). This table can then be used to keep track of user information and verify user access based on further coding.

Where Did Hashing Originate From?

The idea started as a cooking term. In technology, the idea was formed to help guard information against malicious actors attempting to intercept data transmission. The idea is said to have originated at IBM in an internal memorandum written by H.P. Luhn in 1953. The practical application description comes from a study published in the Foundations of Secure Computation in 1978. M. Rabin explicitly discusses cryptographic hash functions and their use in digital signatures.

A year after the Georgia Tech School of Computer Science report was published, Merkle invented Merkle trees for hashing.

What Are the Applications?

  • Encrypt communication between servers and browsers as well as generate session IDs for data caching and online applications
  • Protect sensitive data such as web analytics, usernames, passwords, and payment information
  • Add digital signatures to emails
  • Locate identical or similar data sets through search/lookup functions

Examples in the Real World

Hashing is used on every web-based application that requires encryption for security. It is also extensively used to create and manage blockchain technology. Here are a few specific real-world examples of hash functions:

  • Examining similar data and locating modified files in cloud storage services like Google Drive, OneDrive, and Amazon Cloud
  • Distinguishing records in the GitHub store.
  • Identifying and verifying proof-of-work programs for Bitcoin.

What is Hashing (Hash Function) and How Does it Work? FAQs (Frequently Asked Questions) 

What is hashing?

Hashing is the use of a mathematical function formula to take string input and create a specific length output value to be used as an identifier for encrypted information. It is an essential technology for operating blockchains.

How does a cryptographic hash function work?

Hash functions take input strings and convert them into set length hash values. Both the input and the output are then stored on a data structure known as a hash table. Hash tables map out the key identifiers, and hash values, with the string input. This allows servers to encrypt data for secure use, checksum form information to confirm user identity, and quickly organized/access stored data.

Why is hashing used?

Hashing is used because it is a secure method for encrypting a data structure while also providing the server-side of web applications a method for identifying and verifying access to information or internet applications. As most web-based applications can build up enough data to create duplicate information and hold sensitive private information, service providers need to be able to secure and easily organize information.

As hashing uses mathematical functions and algorithms to organize hash blocks, it is easy and fast to set up and use for server operations.

What hashing algorithm does bitcoin use to hash blocks?

Bitcoin uses the SHA-256 function for its proof-of-work process. SHA is short for Secure Hash Algorithm and was designed by the United States National Security Agency (NSA).

What is the difference between encryption and hashing?

Hash functions are used to identify data on a hash table after it has been defined and established. Hash values that are created to identify and verify information are a one-way process and cannot be reversed to find the original string.

Encryption takes data and creates a jumbled message to be decoded by a cipher. Encrypted messages are designed to be reversible by cipher holders. While hash functions can be used as a method for encrypting information, it is not specific encryption.

Where is the hash function used?

Hash functions are used in hash tables/hash blocks to quickly locate and record data with a specific key value.

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