SubtleCrypto: verify() method

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The verify() method of the SubtleCrypto interface verifies a digital signature.

It takes as its arguments a key to verify the signature with, some algorithm-specific parameters, the signature, and the original signed data. It returns a Promise which will be fulfilled with a boolean value indicating whether the signature is valid.

Syntax

verify(algorithm, key, signature, data)

Parameters

algorithm

A string or object defining the algorithm to use, and for some algorithm choices, some extra parameters. The values given for the extra parameters must match those passed into the corresponding sign() call.

To use RSASSA-PKCS1-v1_5, pass the string "RSASSA-PKCS1-v1_5" or an object of the form { "name": "RSASSA-PKCS1-v1_5" }.
To use RSA-PSS, pass an RsaPssParams object.
To use ECDSA, pass an EcdsaParams object.
To use HMAC, pass the string "HMAC" or an object of the form { "name": "HMAC" }.

key

A CryptoKey containing the key that will be used to verify the signature. It is the secret key for a symmetric algorithm and the public key for a public-key system.

signature

A ArrayBuffer containing the signature to verify.

data

A ArrayBuffer containing the data whose signature is to be verified.

Return value

A Promise that fulfills with a boolean value: true if the signature is valid, false otherwise.

Exceptions

The promise is rejected when the following exception is encountered:

InvalidAccessError DOMException: Raised when the encryption key is not a key for the requested verifying algorithm or when trying to use an algorithm that is either unknown or isn't suitable for a verify operation.

/*
Fetch the contents of the "message" textbox, and encode it
in a form we can use for sign operation.
*/
function getMessageEncoding() {
  const messageBox = document.querySelector(".rsassa-pkcs1 #message");
  let message = messageBox.value;
  let enc = new TextEncoder();
  return enc.encode(message);
}

/*
Fetch the encoded message-to-sign and verify it against the stored signature.
* If it checks out, set the "valid" class on the signature.
* Otherwise set the "invalid" class.
*/
async function verifyMessage(publicKey) {
  const signatureValue = document.querySelector(
    ".rsassa-pkcs1 .signature-value"
  );
  signatureValue.classList.remove("valid", "invalid");

  let encoded = getMessageEncoding();
  let result = await window.crypto.subtle.verify(
    "RSASSA-PKCS1-v1_5",
    publicKey,
    signature,
    encoded
  );

  signatureValue.classList.add(result ? "valid" : "invalid");
}

RSA-PSS

This code uses a public key to verify a signature. See the complete code on GitHub.

/*
Fetch the contents of the "message" textbox, and encode it
in a form we can use for sign operation.
*/
function getMessageEncoding() {
  const messageBox = document.querySelector(".rsa-pss #message");
  let message = messageBox.value;
  let enc = new TextEncoder();
  return enc.encode(message);
}

/*
Fetch the encoded message-to-sign and verify it against the stored signature.
* If it checks out, set the "valid" class on the signature.
* Otherwise set the "invalid" class.
*/
async function verifyMessage(publicKey) {
  const signatureValue = document.querySelector(".rsa-pss .signature-value");
  signatureValue.classList.remove("valid", "invalid");

  let encoded = getMessageEncoding();
  let result = await window.crypto.subtle.verify(
    {
      name: "RSA-PSS",
      saltLength: 32,
    },
    publicKey,
    signature,
    encoded
  );

  signatureValue.classList.add(result ? "valid" : "invalid");
}

ECDSA

This code uses a public key to verify a signature. See the complete code on GitHub.

/*
Fetch the contents of the "message" textbox, and encode it
in a form we can use for sign operation.
*/
function getMessageEncoding() {
  const messageBox = document.querySelector(".ecdsa #message");
  let message = messageBox.value;
  let enc = new TextEncoder();
  return enc.encode(message);
}

/*
Fetch the encoded message-to-sign and verify it against the stored signature.
* If it checks out, set the "valid" class on the signature.
* Otherwise set the "invalid" class.
*/
async function verifyMessage(publicKey) {
  const signatureValue = document.querySelector(".ecdsa .signature-value");
  signatureValue.classList.remove("valid", "invalid");

  let encoded = getMessageEncoding();
  let result = await window.crypto.subtle.verify(
    {
      name: "ECDSA",
      hash: { name: "SHA-384" },
    },
    publicKey,
    signature,
    encoded
  );

  signatureValue.classList.add(result ? "valid" : "invalid");
}

HMAC

This code uses a secret key to verify a signature. See the complete code on GitHub.

/*
Fetch the contents of the "message" textbox, and encode it
in a form we can use for sign operation.
*/
function getMessageEncoding() {
  const messageBox = document.querySelector(".hmac #message");
  let message = messageBox.value;
  let enc = new TextEncoder();
  return enc.encode(message);
}

/*
Fetch the encoded message-to-sign and verify it against the stored signature.
* If it checks out, set the "valid" class on the signature.
* Otherwise set the "invalid" class.
*/
async function verifyMessage(key) {
  const signatureValue = document.querySelector(".hmac .signature-value");
  signatureValue.classList.remove("valid", "invalid");

  let encoded = getMessageEncoding();
  let result = await window.crypto.subtle.verify(
    "HMAC",
    key,
    signature,
    encoded
  );

  signatureValue.classList.add(result ? "valid" : "invalid");
}

Specifications

Specification
Web Cryptography API # SubtleCrypto-method-verify

Browser compatibility

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