AesGcmParams

The AesGcmParams object represents the object that should be passed as the algorithm parameter into the encrypt and decrypt operation when using the AES-GCM algorithm.

For more details, head to the MDN Web Crypto API documentation on AES-GCM.

Properties

Property	Type	Description
name	`string`	Should be set to `AES-GCM`.
iv	`ArrayBuffer`, `TypedArray`, or `DataView`	The initialization vector. It must be 12 bytes long, unpredictable and cryptographically random. It must be unique for every encryption operation carried out with a given key. Never reuse an iv with the same key. Yet, it doesn’t need to be secret and can be transmitted along with the ciphertext.
additionalData (optional)	`ArrayBuffer`, `TypedArray` or `DataView`	Additional data that should be authenticated, but not encrypted. It must be included in the calculation of the authentication tag, but not encrypted itself.
tagLength (optional)	`number`	The length of the authentication tag in bits. Should be set, and will default to 96.

Example

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-GCM',
      length: 256,
    },
    true,
    ['encrypt', 'decrypt']
  );

  /**
   * Encrypt the plaintext using the AES-CBC key with
   * have generated.
   */
  const ciphertext = await crypto.subtle.encrypt(
    {
      name: 'AES-GCM',
      iv: crypto.getRandomValues(new Uint8Array(12)),
    },
    key,
    plaintext
  );
}

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;
}