Class: Hmac
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()andhmac.digest()methods to produce the computed HMAC digest.
The crypto.createHmac() method is used to create Hmac instances. Hmac objects are not to be created directly using the new keyword.
Example: Using Hmac objects as streams:
const crypto = require('crypto');
const hmac = crypto.createHmac('sha256', 'a secret');
hmac.on('readable', () => {
var 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:
const crypto = require('crypto');
const fs = require('fs');
const hmac = crypto.createHmac('sha256', 'a secret');
const input = fs.createReadStream('test.js');
input.pipe(hmac).pipe(process.stdout);Example: Using the hmac.update() and hmac.digest() methods:
const crypto = require('crypto');
const hmac = crypto.createHmac('sha256', 'a secret');
hmac.update('some data to hash');
console.log(hmac.digest('hex'));
// Prints:
// 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
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