deriveBits
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Open source

deriveBits

Caution

The experimental module k6/experimental/webcrypto has graduated, and its functionality is now available globally through the crypto object. The k6/experimental/webcrypto is deprecated and will be removed in the near future.

To migrate your scripts, remove the k6/experimental/webcrypto imports and use the crypto object instead.

It takes as its arguments the base key, the derivation algorithm to use, and the length of the bits to derive. It returns a Promise which will be fulfilled with an ArrayBuffer containing the derived bits. This array of bits can be used as a key for encryption or decryption as a shared secret.

Usage

deriveBits(algorithm, baseKey, length)

Parameters

NameTypeDescription
algorithmEcdhKeyDeriveParamsAn object defining a derivation algorithm to use.
baseKeyCryptoKeyRepresent an input to derivation algorithm. Currently it could be only a private ECDH key.
lengthnumberOptional. A length of the bits to derive. Currently, only multiplies of 8 are supported.

Supported algorithms

ECDHHKDFPBKDF2
✅ EcdhKeyDeriveParams❌❌

Return Value

A Promise that resolves to a new ArrayBuffer containing the derived bits.

Example

JavaScript 
import { crypto } from 'k6/experimental/webcrypto';

export default async function () {
  // Generate a key pair for Alice
  const aliceKeyPair = await crypto.subtle.generateKey(
    {
      name: 'ECDH',
      namedCurve: 'P-256',
    },
    true,
    ['deriveKey', 'deriveBits']
  );

  // Generate a key pair for Bob
  const bobKeyPair = await crypto.subtle.generateKey(
    {
      name: 'ECDH',
      namedCurve: 'P-256',
    },
    true,
    ['deriveKey', 'deriveBits']
  );

  // Derive shared secret for Alice
  const aliceSharedSecret = await deriveSharedSecret(aliceKeyPair.privateKey, bobKeyPair.publicKey);

  // Derive shared secret for Bob
  const bobSharedSecret = await deriveSharedSecret(bobKeyPair.privateKey, aliceKeyPair.publicKey);

  console.log('alice shared secret: ' + printArrayBuffer(aliceSharedSecret));
  console.log('bob shared secret: ' + printArrayBuffer(bobSharedSecret));
}

async function deriveSharedSecret(privateKey, publicKey) {
  return crypto.subtle.deriveBits(
    {
      name: 'ECDH',
      public: publicKey,
    },
    privateKey,
    256
  );
}

const printArrayBuffer = (buffer) => {
  const view = new Uint8Array(buffer);
  return Array.from(view);
};