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  3. Node.js — Calculate a SHA256 Hash

Node.js — Calculate a SHA256 Hash

Node.js comes with a built-in crypto module and a bundled version of OpenSSL. The crypto module wraps OpenSSL providing an API for cryptographic functions.

Node.js’ crypto module provides a createHash method allowing you to calculate hashes of given content. This tutorial shows you how to use the createHash method to calculate a SHA256 hash.

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Hash a Value in Node.js Using SHA256

Import the createHash function from the Node.js crypto module. Calling createHash requires the hash algorithm name as an argument. The return value of that call is a Hash instance that you can use to calculate a hash value for a given input.

Here’s a code snippet calculating and returning a SHA256 hash of content:

import { createHash } from 'node:crypto'

/**
 * Returns a SHA256 hash using SHA-2 for the given `content`.
 *
 * @see https://en.wikipedia.org/wiki/SHA-2
 * 
 * @param {String} content
 *
 * @returns {String}
 */
function sha256(content) {  
  return createHash('sha256').update(content).digest('hex')
}

We used Node.js v16 to write this tutorial. Node.js v16 uses SHA-2 (Secure Hash Algorithm 2) (created by the United States National Security Agency) to calculate the hash value. The SHA-2 hash algorithm is still considered secure by the security community.

Using SHA3-256 to Calculate a Hash

The SHA-3 hash algorithm is the latest member of the Secure Hash Algorithm family. SHA-3 was originally called “Keccak”. The Keccak algorithm is the winner in the NIST hash function competition.

Node.js (using OpenSSL) supports calculating a SHA256 hash using the SHA-3 algorithm. You can switch the hash function from SHA-2 to SHA-3 by passing the sha3-256 identifier to Node.js’ createHash function:

import { createHash } from 'node:crypto'

/**
 * Returns a SHA256 hash using SHA-3 for the given `content`.
 *
 * @see https://en.wikipedia.org/wiki/SHA-3
 *
 * @param {String} content
 *
 * @returns {String}
 */
function sha256(content) {  
  return createHash('sha3-256').update(content).digest('hex')
}

This calculate a SHA256 hash using the algorithm from the SHA-3 family. You can find more details for and comparisons of secure hash algorithms on this linked Wikipedia page.

Enjoy!

PS: Here’s an interesting read on Stackoverflow outlining the differences between SHA-2 and SHA-3.

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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