The value "NaN" is invalid for option "size" about pbkdf2

[webmaster128]

So this should raise a helpful error message when you input an unsupported digest string? In the sync version only those strings are supported with no aliases:

var sizes = {
  md5: 16,
  sha1: 20,
  sha224: 28,
  sha256: 32,
  sha384: 48,
  sha512: 64,
  rmd160: 20,
  ripemd160: 20
}

Thanks, I think that explains it.