decrypt

The decrypt() method decrypts some encrypted data.

Usage

decrypt(algorithm, key, data)

Parameters

Name	Type	Description
`algorithm`	AesCbcParams, AesCtrParams, or AesGcmParams object	Defines the algorithm to use and any extra-parameters. The values given for the extra parameters must match those used in the corresponding [encrypt] call.
`key`	CryptoKey	The key to use for decryption.
`data`	`ArrayBuffer`, `TypedArray`, or `DataView`	The encrypted data to be decrypted (also known as ciphertext).

Supported algorithms

AES-CBC	AES-CTR	AES-GCM	RSA-OAEP
✅ AesCbcParams	✅ AesCtrParams	✅ AesGcmParams	✅ RsaOaepParams

Return Value

A Promise that resolves to a new ArrayBuffer containing the decrypted data.

Throws

Type	Description
`InvalidAccessError`	Raised when the requested operation is not valid with the provided key. For instance when an invalid encryption algorithm is used, or a key not matching the selected algorithm is provided.
`OperationError`	Raised when the operation failed for an operation-specific reason. For instance, if the algorithm size is invalid, or errors occurred during the process of decrypting the ciphertext.

Example

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

export default async function () {
  const plaintext = stringToArrayBuffer('Hello, World!');

  /**
   * Generate a symmetric key using the AES-CBC algorithm.
   */
  const key = await crypto.subtle.generateKey(
    {
      name: 'AES-CBC',
      length: 256,
    },
    true,
    ['encrypt', 'decrypt']
  );

  /**
   * Encrypt the plaintext using the AES-CBC key with
   * have generated.
   */
  const iv = crypto.getRandomValues(new Uint8Array(16));
  const ciphertext = await crypto.subtle.encrypt(
    {
      name: 'AES-CBC',
      iv: iv,
    },
    key,
    plaintext
  );

  /**
   * Decrypt the ciphertext using the same key to verify
   * that the resulting plaintext is the same as the original.
   */
  const deciphered = await crypto.subtle.decrypt(
    {
      name: 'AES-CBC',
      iv: iv,
    },
    key,
    ciphertext
  );

  console.log(
    'deciphered text == original plaintext: ',
    arrayBufferToHex(deciphered) === arrayBufferToHex(plaintext)
  );
}

function arrayBufferToHex(buffer) {
  return [...new Uint8Array(buffer)].map((x) => x.toString(16).padStart(2, '0')).join('');
}

function stringToArrayBuffer(str) {
  const buf = new ArrayBuffer(str.length * 2); // 2 bytes for each char
  const bufView = new Uint16Array(buf);
  for (let i = 0, strLen = str.length; i < strLen; i++) {
    bufView[i] = str.charCodeAt(i);
  }
  return buf;
}