crypto.pbkdf2(password, salt, iterations, keylen[, digest], callback)
Provides an asynchronous Password-Based Key Derivation Function 2 (PBKDF2) implementation. A selected HMAC digest algorithm specified by digest is applied to derive a key of the requested byte length (keylen) from the password, salt and iterations. If the digest algorithm is not specified, a default of 'sha1' is used.
The supplied callback function is called with two arguments: err and derivedKey. If an error occurs, err wil