Use the generateKey() method of the SubtleCrypto interface to generate a new key (for symmetric algorithms) or key pair (for public-key algorithms).

algorithm

An object defining the type of key to generate and providing extra algorithm-specific parameters.

• For RSASSA-PKCS1-v1_5, RSA-PSS, or RSA-OAEP: pass an RsaHashedKeyGenParams object.
• For ECDSA or ECDH: pass an EcKeyGenParams object.
• For HMAC: pass an HmacKeyGenParams object.
• For AES-CTR, AES-CBC, AES-GCM, or AES-KW: pass an AesKeyGenParams object.

extractable

A boolean value indicating whether it will be possible to export the key using SubtleCrypto.exportKey() or SubtleCrypto.wrapKey().

keyUsages

An Array indicating what can be done with the newly generated key. Possible values for array elements are:

• encrypt: The key may be used to encrypt messages.
• decrypt: The key may be used to decrypt messages.
• sign: The key may be used to sign messages.
• verify: The key may be used to verify signatures.
• deriveKey: The key may be used in deriving a new key.
• deriveBits: The key may be used in deriving bits.
• wrapKey: The key may be used to wrap a key.
• unwrapKey: The key may be used to unwrap a key.

A Promise that fulfills with a CryptoKey (for symmetric algorithms) or a CryptoKeyPair (for public-key algorithms).

The promise is rejected when the following exception is encountered:

SyntaxError DOMException

Raised when the result is a CryptoKey of type secret or private but keyUsages is empty.

SyntaxError DOMException

Raised when the result is a CryptoKeyPair and its privateKey.usages attribute is empty.

This code generates an RSA-OAEP encryption key pair. See the complete code on GitHub.

let keyPair = await window.crypto.subtle.generateKey(
  {
    name: "RSA-OAEP",
    modulusLength: 4096,
    publicExponent: new Uint8Array([1, 0, 1]),
    hash: "SHA-256",
  },
  true,
  ["encrypt", "decrypt"],
);

This code generates an ECDSA signing key pair. See the complete code on GitHub.

let keyPair = await window.crypto.subtle.generateKey(
  {
    name: "ECDSA",
    namedCurve: "P-384",
  },
  true,
  ["sign", "verify"],
);

This code generates an HMAC signing key. See the complete code on GitHub.

let key = await window.crypto.subtle.generateKey(
  {
    name: "HMAC",
    hash: { name: "SHA-512" },
  },
  true,
  ["sign", "verify"],
);

This code generates an AES-GCM encryption key. See the complete code on GitHub.

let key = await window.crypto.subtle.generateKey(
  {
    name: "AES-GCM",
    length: 256,
  },
  true,
  ["encrypt", "decrypt"],
);

• Cryptographic key length recommendations.
• NIST Transitioning the Use of Cryptographic Algorithms and Key Lengths.