What is Node crypto.createPrivateKey(key)?

crypto.createPrivateKey is a function that accepts one argument and returns a new key (object(KeyObject)) that contains a private key.

   crypto.createPrivateKey(key)

Thecrypto.createPrivatekey function was added in node version 11.6.0, earlier versions of node don’t support this function.

Parameter

If the key is not a string or buffer, then the key must be an object with the following properties.

• key: The key material can either be in the PEM, DER, or JWK format. Key can be an instance of any of the following:
  • string
  • ArrayBuffer
  • Buffer
  • TypedArray
  • DataView
  • Object
• format : Must be pemprivacy-enhanced mail, derdistinguished encoding rules, or jwkjson web key. The Default format is pem and the format must be a string.
• type : Must be pkcs1public key cryptographic standards 1 , pkcs8public key cryptographic standards 8, or sec1standards for efficient cryptography 1. This option is only required if the format is der; otherwise, it is ignored. The type must be a string.
• passphrase : Passphrase is used for decryption. If the private key is encrypted, a passphrase must be specified. The length of the passphrase is limited to 1024 bytes. Passphrase must be either a string or Buffer.
• encoding : The string encoding to be used when key is a string.

Return value

The crypto.createPrivateKey function returns a new Key Object.

Example

The code snippet below shows how to use the crypto.createPrivateKey function. The createPrivateKey function uses the key argument to create and return a new key object.

Explanation

1. Import crypto module.
2. Use the crypto.generateKeyPairSync function to synchronously get privateKey.

• Finally, pass the private key generated from the crypto.generateKeyPairSync to the crypto.createPrivateKey function. This, in turn, returns a keyObject.
• The last line exports the keyObject; thus, making it available for use on other modules.