It's probably more than just some hash verification. a lot of firmwares are signed with the manufactures master code.
Digital signatures either involve encrypting the whole file, or more commonly using a hash which is then encrypted. See the History section here: http://en.wikipedia.org/wiki/Digital_signature
Also, strong hashes use crypto techniques anyway to minimize the chances of collisions and thus undetected errors, which is why all of the modern ones come from crypto researchers. Either way it's kind of "a rose by any other name".
A bit of research on npk reveals a lightweight packaging system http://code.google.com/p/npk/
which uses a block cipher called xxtea (http://en.wikipedia.org/wiki/XXTEA
) for content verification. The wiki page doesn't include enough details to tell how they're using it, or if MicroTik's npk is the same.