AesCtrParams

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

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

Properties

Property	Type	Description
name	`string`	Should be set to `AES-CTR`.
counter	`ArrayBuffer`, `TypedArray`, or `DataView`	The initial value of the counter block. This must be 16-bytes long, like the AES block size.
length	`number`	The number of bits in the counter block that are used for the actual counter. It is recommended to use 64 (half of the counter block).

Example

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

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

  /**
   * Encrypt the plaintext using the AES-CTR key with
   * have generated.
   */
  const ciphertext = await crypto.subtle.encrypt(
    {
      name: 'AES-CTR',
      counter: crypto.getRandomValues(new Uint8Array(16)),
      length: 128,
    },
    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;
}