Node crypto.createPrivateKey function | API Reference | Bun

Creates and returns a new key object containing a private key. If key is a string or Buffer, format is assumed to be 'pem'; otherwise, key must be an object with the properties described above.

If the private key is encrypted, a passphrase must be specified. The length of the passphrase is limited to 1024 bytes.

Node.js uses a KeyObject class to represent a symmetric or asymmetric key, and each kind of key exposes different functions. The createSecretKey, createPublicKey and createPrivateKey methods are used to create KeyObjectinstances. KeyObject objects are not to be created directly using the newkeyword.

Most applications should consider using the new KeyObject API instead of passing keys as strings or Buffers due to improved security features.

KeyObject instances can be passed to other threads via postMessage(). The receiver obtains a cloned KeyObject, and the KeyObject does not need to be listed in the transferList argument.

This property exists only on asymmetric keys. Depending on the type of the key, this object contains information about the key. None of the information obtained through this property can be used to uniquely identify a key or to compromise the security of the key.

For RSA-PSS keys, if the key material contains a RSASSA-PSS-params sequence, the hashAlgorithm, mgf1HashAlgorithm, and saltLength properties will be set.

Other key details might be exposed via this API using additional attributes.

For asymmetric keys, this property represents the type of the key. See the supported asymmetric key types.

This property is undefined for unrecognized KeyObject types and symmetric keys.

For secret keys, this property represents the size of the key in bytes. This property is undefined for asymmetric keys.

Depending on the type of this KeyObject, this property is either'secret' for secret (symmetric) keys, 'public' for public (asymmetric) keys or 'private' for private (asymmetric) keys.

Returns true or false depending on whether the keys have exactly the same type, value, and parameters. This method is not constant time.

A KeyObject with which to compare keyObject.

For symmetric keys, the following encoding options can be used:

For public keys, the following encoding options can be used:

For private keys, the following encoding options can be used:

The result type depends on the selected encoding format, when PEM the result is a string, when DER it will be a buffer containing the data encoded as DER, when JWK it will be an object.

When JWK encoding format was selected, all other encoding options are ignored.

PKCS#1, SEC1, and PKCS#8 type keys can be encrypted by using a combination of the cipher and format options. The PKCS#8 type can be used with anyformat to encrypt any key algorithm (RSA, EC, or DH) by specifying acipher. PKCS#1 and SEC1 can only be encrypted by specifying a cipherwhen the PEM format is used. For maximum compatibility, use PKCS#8 for encrypted private keys. Since PKCS#8 defines its own encryption mechanism, PEM-level encryption is not supported when encrypting a PKCS#8 key. See RFC 5208 for PKCS#8 encryption and RFC 1421 for PKCS#1 and SEC1 encryption.

Converts a KeyObject instance to a CryptoKey.

Example: Converting a CryptoKey instance to a KeyObject:

const { KeyObject } = await import('node:crypto');
const { subtle } = globalThis.crypto;

const key = await subtle.generateKey({
name: 'HMAC',
hash: 'SHA-256',
length: 256,
}, true, ['sign', 'verify']);

const keyObject = KeyObject.from(key);
console.log(keyObject.symmetricKeySize);
// Prints: 32 (symmetric key size in bytes)