The critical point here is that it is trivial to obtain IDSold
Gn with the information of F(IDSoldGn). Note that if the
characteristic polynomial of an L-bit LFSR and L respective
output bits are known, then the seed of the LFSR can be
easily found by a bitwise matrix multiplication. Namely, the
characteristics of the polynomial LFSR is known and public.
Therefore, an LFSR alone cannot bring obscurity to the system
as claimed in the paper.