I was doing it in GF(2^32-5). Your statement is true for GF(2^n) where n is small enough to keep the entire multiplication-table in memory (usually n <= 8). Whe

I was doing it in GF(2^32-5). Your statement is true for GF(2^n) where n is small enough to keep the entire multiplication-table in memory (usually n <= 8). When it's bigger you keep log-tables in memory then sign matters. However when n=16 you get lucky and can use char as an unsigned 16 bit int.