def ns2block(ns):
    """ Convert N1 and N2 integers to 8-byte block
    """
    n1, n2 = ns
    return bytes(bytearray((n2 >> 0 & 255, n2 >> 8 & 255, n2 >> 16 & 255, 
        n2 >> 24 & 255, n1 >> 0 & 255, n1 >> 8 & 255, n1 >> 16 & 255, n1 >>
        24 & 255)))
