'Similar to shift_rows above, but performed in inverse for decryption.'

def shift_rows_inv(self, b):

    (b[5], b[9], b[13], b[1]) = (b[1], b[5], b[9], b[13])
    (b[10], b[14], b[2], b[6]) = (b[2], b[6], b[10], b[14])
    (b[15], b[3], b[7], b[11]) = (b[3], b[7], b[11], b[15])
