sign

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Open source

sign

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

Usage 

sign(algorithm, key, data)

Parameters

NameTypeDescription
algorithmstring 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.
keyCryptoKeyThe key to use for signing.
dataArrayBuffer, TypedArray, or DataViewThe data to be signed.

Supported algorithms

ECDSAHMACRSASSA-PKCS1-v1_5RSA-PSS
✅ EcdsaParams✅ HmacKeyGenParams✅✅ RsaPssParams

Return Value

A Promise that resolves with the signature as an ArrayBuffer.

Throws

TypeDescription
InvalidAccessErrorRaised 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);
};