• options: {Object}
    • Returns: {string | Buffer}

    For symmetric keys, this function allocates a Buffer containing the key material and ignores any options.

    For asymmetric keys, the options parameter is used to determine the export format.

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

    • type: {string} Must be one of 'pkcs1' (RSA only) or 'spki'.
    • format: {string} Must be 'pem' or 'der'.

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

    • type: {string} Must be one of 'pkcs1' (RSA only), 'pkcs8' or 'sec1' (EC only).
    • format: {string} Must be 'pem' or 'der'.
    • cipher: {string} If specified, the private key will be encrypted with the given cipher and passphrase using PKCS#5 v2.0 password based encryption.
    • passphrase: {string | Buffer} The passphrase to use for encryption, see cipher.

    When PEM encoding was selected, the result will be a string, otherwise it will be a buffer containing the data encoded as DER.

    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 any format to encrypt any key algorithm (RSA, EC, or DH) by specifying a cipher. PKCS#1 and SEC1 can only be encrypted by specifying a cipher when 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.