sign

The sign() operation generates a digital signature of the provided data, using the given CryptoKey object.

Usage

sign(algorithm, key, data)

Parameters

Name	Type	Description
`algorithm`	`string` or object with a single `name` string property (`{name: "RSASSA-PKCS1-v1_5"}`) or an EcdsaParams, HmacKeyGenParams, or RsaPssParams object.	The signature algorithm to use.
`key`	CryptoKey	The key to use for signing.
`data`	`ArrayBuffer`, `TypedArray`, or `DataView`	The data to be signed.

Supported algorithms

ECDSA	HMAC	RSASSA-PKCS1-v1_5	RSA-PSS
✅ EcdsaParams	✅ HmacKeyGenParams	✅	✅ RsaPssParams

Return Value

A Promise that resolves with the signature as an ArrayBuffer.

Throws

Type	Description
`InvalidAccessError`	Raised when the signing key either does not support signing operation, or is incompatible with the selected algorithm.

Examples

Signing data with HMAC key

JavaScript
export default async function () {
  const generatedKey = await crypto.subtle.generateKey(
    {
      name: 'HMAC',
      hash: { name: 'SHA-1' },
    },
    true,
    ['sign', 'verify']
  );

  const data = string2ArrayBuffer('Hello World');

  /**
   * Signes the encoded data with the provided key using the HMAC algorithm
   * the returned signature can be verified using the verify method.
   */
  const signature = await crypto.subtle.sign('HMAC', generatedKey, data);

  /**
   * Verifies the signature of the encoded data with the provided key using the HMAC algorithm.
   */
  const verified = await crypto.subtle.verify('HMAC', generatedKey, signature, data);

  console.log('verified: ', verified);
}

function string2ArrayBuffer(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;
}

Signing and verifying data with ECDSA

JavaScript
export default async function () {
  const keyPair = await crypto.subtle.generateKey(
    {
      name: 'ECDSA',
      namedCurve: 'P-256',
    },
    true,
    ['sign', 'verify']
  );

  const data = string2ArrayBuffer('Hello World');

  const alg = { name: 'ECDSA', hash: { name: 'SHA-256' } };

  // makes a signature of the encoded data with the provided key
  const signature = await crypto.subtle.sign(alg, keyPair.privateKey, data);

  console.log('signature: ', printArrayBuffer(signature));

  //Verifies the signature of the encoded data with the provided key
  const verified = await crypto.subtle.verify(alg, keyPair.publicKey, signature, data);

  console.log('verified: ', verified);
}

const string2ArrayBuffer = (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;
};

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