Hmac - crypto - Node

class Hmac

extends stream.Transform

Usage in Deno

import { Hmac } from "node:crypto";

Deprecated

Since v20.13.0 Calling Hmac class directly with Hmac() or new Hmac() is deprecated due to being internals, not intended for public use. Please use the createHmac method to create Hmac instances.

The Hmac class is a utility for creating cryptographic HMAC digests. It can be used in one of two ways:

As a stream that is both readable and writable, where data is written to produce a computed HMAC digest on the readable side, or
Using the hmac.update() and hmac.digest() methods to produce the computed HMAC digest.

The createHmac method is used to create Hmac instances. Hmacobjects are not to be created directly using the new keyword.

Example: Using Hmac objects as streams:

const {
  createHmac,
} = await import('node:crypto');

const hmac = createHmac('sha256', 'a secret');

hmac.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = hmac.read();
  if (data) {
    console.log(data.toString('hex'));
    // Prints:
    //   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
  }
});

hmac.write('some data to hash');
hmac.end();

Example: Using Hmac and piped streams:

import { createReadStream } from 'node:fs';
import { stdout } from 'node:process';
const {
  createHmac,
} = await import('node:crypto');

const hmac = createHmac('sha256', 'a secret');

const input = createReadStream('test.js');
input.pipe(hmac).pipe(stdout);

Example: Using the hmac.update() and hmac.digest() methods:

const {
  createHmac,
} = await import('node:crypto');

const hmac = createHmac('sha256', 'a secret');

hmac.update('some data to hash');
console.log(hmac.digest('hex'));
// Prints:
//   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e

Constructors

new



Hmac()

Methods



digest(): Buffer

Calculates the HMAC digest of all of the data passed using hmac.update(). If encoding is provided a string is returned; otherwise a Buffer is returned;

The Hmac object can not be used again after hmac.digest() has been called. Multiple calls to hmac.digest() will result in an error being thrown.



digest(encoding: BinaryToTextEncoding): string



update(data: BinaryLike): Hmac

Updates the Hmac content with the given data, the encoding of which is given in inputEncoding. If encoding is not provided, and the data is a string, an encoding of 'utf8' is enforced. If data is a Buffer, TypedArray, orDataView, then inputEncoding is ignored.

This can be called many times with new data as it is streamed.



update(data: string,
inputEncoding: Encoding,
): Hmac