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How Hashing Algorithms Work

how hashing algoriths work

Hashing algorithms are most important in cryptography to secure password and more. Find out what hashing algorithms are, avalanche effect and how they work with examples.

A file has to be forwarded to the destination. So how will you send it and be sure that it will reach the destination intact? You may send the file and then contact the recipient to check if they have received it. However, it may not always be possible to contact the person at the other end. Another option is to send multiple versions of the file and hope that one of them would reach the destination. But none of these is foolproof. Anyone in between may have a sneak peek into the files and gather some crucial information. So, what is the option left to you? Yes, it is the hashing algorithm that will translate the input into a code, and someone may compare the information and the output to confirm that they are the same. Let us start by understanding what hashing is.

What is hashing?

Hashing is a process that generates a result of fixed length from a given input. The output is called the hash value and is a summary of the original data. It could be taking an image and printing it on a piece of paper and then folding and crumpling it to such an extent that no third-party would be able to read it without knowing the initial data.

A file usually carries blocks of data. Hashing will transform this data into a string or a key that is an image of the original data. The function translates the data into a shorter fixed-length value that is derived from the original string. If you are using an excellent hashing algorithm, there will be an avalanche effect that changes the output significantly even when there is a little change in the input data like below.

avalanche effect

Let us use a basic example to see how hashing algorithms work.

Input Number: 498,297

Hashing Algorithm: Input# x 135

Hash Value: 67, 270, 095

hashing algorithmHowever, in reality, the calculation will not be so easy. There could be numerous functions involved in between to arrive at the final hash value. The better the algorithm used, the more difficult it will be for someone to comprehend the output without the private key.

The hashing function forms the crux of the algorithm.

The Hashing Algorithm

This algorithm is a cryptographic hash function. It is known to map the data if any size to an output of fixed size. It has been designed to be impossible to invert, but some of the hash algorithms can be breached through unauthorized access. Ideally. The hashing function must create the hash value of any input within a short time and must be impossible to regenerate the data from the hash value. Moreover, care must be taken so that there are no similar hash values from different input data.

hash function structure

The hashing function takes in a fixed length of data, and these data blocks can vary across the different algorithms. However, in a few cases, the messages would not be in the multiples of the fixed data block size. In such a case, a technology called padding is used.  The padding technique helps to break the entire message into fixed data block sizes.

the avalanche effect

The output of the first block is fed to the input of the second block. In this way, the output from the last data block is a combination of all the data blocks. Any change in any of the data blocks leads to a change in the entire hash value. It is the avalanche effect.

Few applications of hashing

Verifying passwords

This procedure is used in verifying of passwords. What we do to login to any software is to use our user credentials. When we enter the password, a hash of the password is created and sent to the server for verification. The server also contains a hash value of the password, and both are compared.

Compiler operation

Various programming languages have hash table-based data structures. If you have to differentiate between the keywords and compile the program, the keywords are stored in a set by the compiler and are implemented with the help of a hash table.

Some popular hashing algorithms

Message Digest (MD) Algorithm

The term “message digest” refers to a hash value or a short string that is of fixed length and is computed from a longer variable-length message that is being hashed. The algorithm is used to create a digital signature from a message. The MD5 is a faster version that produces an output value of 128 bits.

The algorithm is dependent on hash functions for generating a unique value computed from the data along with a unique symmetric key. The unique symmetric key is shared between the sender and the receiver to create a value that provides the required confidentiality.

However, it is rather easy to crack by pushing a malicious code while providing the same hash value. These days, it can be broken into using a search engine.

Secure Hash Algorithm (SHA)

Also known as SHA, it is  an algorithm that consists of modular additions, bitwise operations, and compression functions. The input data is converted to a hashing function that is a fixed-sized string that is different from the input. It is also used to encrypt passwords as the server will keep track of the hash value of the password. It also exhibits the avalanche effect where a small change in input leads to a profound difference in the output. It also helps in detecting possible tampering of data as the hash value from the tampered file will be different from the original one.


The hashing algorithms are being used in advanced technologies too. For example, the SHA-256 algorithm is used in the blockchain technology. Bitcoin also uses the SHA-256 algorithm and runs two iterations of the same. The latest versions of these algorithms can fox the hackers and prevent them from getting unauthorized access and succeeding in a data breach. They evolve continuously and are gradually replaced by the later versions. In this article, we had a sneak peek into how hashing algorithms work. We expect newer and more stringent versions of these algorithms in future.

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