Web/API/SubtleCrypto/exportKey

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

The exportKey() method of the SubtleCrypto interface exports a key: that is, it takes as input a CryptoKey object and gives you the key in an external, portable format.

To export a key, the key must have CryptoKey.extractable set to true.

Keys can be exported in several formats: see Supported formats in the SubtleCrypto.importKey() page for details.

Keys are not exported in an encrypted format: to encrypt keys when exporting them use the SubtleCrypto.wrapKey() API instead.

Syntax

const result = crypto.subtle.exportKey(format, key);

Parameters

format is a string value describing the data format in which the key should be exported. It can be one of the following:
- raw: Raw format.
- pkcs8: PKCS #8 format.
- spki: SubjectPublicKeyInfo format.
- jwk: JSON Web Key format.
key is the CryptoKey to export.

Return value

result is a Promise.
- If format was jwk, then the promise fulfills with a JSON object containing the key.
- Otherwise the promise fulfills with an ArrayBuffer containing the key.

Exceptions

The promise is rejected when one of the following exceptions is encountered:

InvalidAccessError: Raised when trying to export a non-extractable key.
NotSupported: Raised when trying to export in an unknown format.
TypeError: Raised when trying to use an invalid format.

Examples

Note: You can [[../../../../../../../mdn.github.io/dom-examples/web-crypto/export-key/index|try the working examples]] out on GitHub.

Raw export

This example exports an AES key as an ArrayBuffer containing the bytes for the key. See the complete code on GitHub.

/*
Export the given key and write it into the "exported-key" space.
*/
async function exportCryptoKey(key) {
  const exported = await window.crypto.subtle.exportKey(
    "raw",
    key
  );
  const exportedKeyBuffer = new Uint8Array(exported);

  const exportKeyOutput = document.querySelector(".exported-key");
  exportKeyOutput.textContent = `[${exportedKeyBuffer}]`;
}

/*
Generate an encrypt/decrypt secret key,
then set up an event listener on the "Export" button.
*/
window.crypto.subtle.generateKey(
  {
    name: "AES-GCM",
    length: 256,
  },
  true,
  ["encrypt", "decrypt"]
).then((key) => {
  const exportButton = document.querySelector(".raw");
  exportButton.addEventListener("click", () => {
    exportCryptoKey(key);
  });
});

PKCS #8 export

This example exports an RSA private signing key as a PKCS #8 object. The exported key is then PEM-encoded. See the complete code on GitHub.

/*
Convert  an ArrayBuffer into a string
from https://developers.google.com/web/updates/2012/06/How-to-convert-ArrayBuffer-to-and-from-String
*/
function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint8Array(buf));
}

/*
Export the given key and write it into the "exported-key" space.
*/
async function exportCryptoKey(key) {
  const exported = await window.crypto.subtle.exportKey(
    "pkcs8",
    key
  );
  const exportedAsString = ab2str(exported);
  const exportedAsBase64 = window.btoa(exportedAsString);
  const pemExported = `-----BEGIN PRIVATE KEY-----\n${exportedAsBase64}\n-----END PRIVATE KEY-----`;

  const exportKeyOutput = document.querySelector(".exported-key");
  exportKeyOutput.textContent = pemExported;
}

/*
Generate a sign/verify key pair,
then set up an event listener on the "Export" button.
*/
window.crypto.subtle.generateKey(
  {
    name: "RSA-PSS",
    // Consider using a 4096-bit key for systems that require long-term security
    modulusLength: 2048,
    publicExponent: new Uint8Array([1, 0, 1]),
    hash: "SHA-256",
  },
  true,
  ["sign", "verify"]
).then((keyPair) => {
  const exportButton = document.querySelector(".pkcs8");
  exportButton.addEventListener("click", () => {
    exportCryptoKey(keyPair.privateKey);
  });

});

SubjectPublicKeyInfo export

This example exports an RSA public encryption key as a PEM-encoded SubjectPublicKeyInfo object. See the complete code on GitHub.

/*
Convert  an ArrayBuffer into a string
from https://developers.google.com/web/updates/2012/06/How-to-convert-ArrayBuffer-to-and-from-String
*/
function ab2str(buf) {
  return String.fromCharCode.apply(null, new Uint8Array(buf));
}

/*
Export the given key and write it into the "exported-key" space.
*/
async function exportCryptoKey(key) {
  const exported = await window.crypto.subtle.exportKey(
    "spki",
    key
  );
  const exportedAsString = ab2str(exported);
  const exportedAsBase64 = window.btoa(exportedAsString);
  const pemExported = `-----BEGIN PUBLIC KEY-----\n${exportedAsBase64}\n-----END PUBLIC KEY-----`;

  const exportKeyOutput = document.querySelector(".exported-key");
  exportKeyOutput.textContent = pemExported;
}

/*
Generate an encrypt/decrypt key pair,
then set up an event listener on the "Export" button.
*/
window.crypto.subtle.generateKey(
  {
    name: "RSA-OAEP",
    // Consider using a 4096-bit key for systems that require long-term security
    modulusLength: 2048,
    publicExponent: new Uint8Array([1, 0, 1]),
    hash: "SHA-256",
  },
  true,
  ["encrypt", "decrypt"]
).then((keyPair) => {
  const exportButton = document.querySelector(".spki");
  exportButton.addEventListener("click", () => {
    exportCryptoKey(keyPair.publicKey);
  });
});

JSON Web Key import

This code exports an ECDSA private signing key as a JSON Web Key object. See the complete code on GitHub.

/*
Export the given key and write it into the "exported-key" space.
*/
async function exportCryptoKey(key) {
  const exported = await window.crypto.subtle.exportKey(
    "jwk",
    key
  );
  const exportKeyOutput = document.querySelector(".exported-key");
  exportKeyOutput.textContent = JSON.stringify(exported, null, " ");
 }

/*
Generate a sign/verify key pair,
then set up an event listener on the "Export" button.
*/
window.crypto.subtle.generateKey(
  {
    name: "ECDSA",
    namedCurve: "P-384"
  },
  true,
  ["sign", "verify"]
).then((keyPair) => {
  const exportButton = document.querySelector(".jwk");
  exportButton.addEventListener("click", () => {
    exportCryptoKey(keyPair.privateKey);
  });

});

Specifications

Specification	Status	Comment
Web Cryptography APIThe definition of 'SubtleCrypto.exportKey()' in that specification.	Recommendation	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`exportKey`	Chrome Full support 37	Edge Partial support 12 Notes' Partial support 12 Notes' Notes' Not supported: RSA-PSS, ECDSA, ECDH. Notes' Not supported: AES-CTR.	Firefox Full support 34 Full support 34 No support 32 — 34 Disabled' Disabled' From version 32 until version 34 (exclusive): this feature is behind the `dom.webcrypto.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE Partial support 11 Notes' Partial support 11 Notes' Notes' Returns `KeyOperation` instead of `Promise`	Opera Full support 24	Safari Full support 7	WebView Android Full support 37	Chrome Android Full support 37	Firefox Android Full support 34 Full support 34 No support 32 — 34 Disabled' Disabled' From version 32 until version 34 (exclusive): this feature is behind the `dom.webcrypto.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 24	Safari iOS Full support 7	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
Partial support: Partial support
See implementation notes.': See implementation notes.
User must explicitly enable this feature.': User must explicitly enable this feature.