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Node.js crypto.createHash() method — A Comprehensive Guide

What is the Node.js crypto.createHash() method? - cover image

In Node.js, the ⁣crypto.createHash() method is a built-in method in the crypto module that creates and returns a hash object that can be used to generate a hash of data using a specific hashing algorithm.

How to use the createHash() function?

To use this method, we first import the crypto module and then create a Hash instance where we specify which hashing algorithm we want to use. Some of the common algorithms supported by this method include⁣ md5, sha1, sha256, sha512. We can also update the data to generate a new hash digest (aka the output produced by the hash function).

Let’s understand how the createHash() method works using an example.

const crypto = require('crypto');

const data = 'metaschool is cool';
const hash = crypto.createHash('sha256');

hash.update(data);

const digest = hash.digest('hex');

console.log(digest);

Explanation

  • crypto module provides cryptographic functionalities in Node.js.
  • crypto.createHash('sha256') creates a Hash instance configured to use the SHA-256 algorithm.
  • update() method feeds data into the hash object. This method can be called multiple times if the data is streamed or in chunks.
  • digest('hex') method calculates the hash of the data provided to the update() method and returns it in the specified encoding format, in this case, hexadecimal.

The More You Know

  • Choose a hashing algorithm that meets your security requirements. For instance, SHA-256 is generally more secure than MD5 and SHA-512 is more secure than SHA-256.
  • The update() method accepts strings, Buffer, TypedArray, or DataView objects. When providing a string, you can specify the encoding (e.g., 'utf8').
  • Once digest() is called, the Hash object cannot be used again. If you want to hash more data, you need to create a new Hash instance.
  • Hash algorithms are designed to be one-way functions, which means that it is computationally impossible to generate the original data from the hash.
  • A hash collision is when two different pieces of input data produce the same hash digest. Although these are extremely rare for most hash algorithms, hash collisions can still happen.

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