Finite fields in Maxima?



I discovered an old article from SIGSAM 1989: "Finite Field Manipulations in
Macsyma" by Kevin T. Rowney and Robert D. Silverman.  I would love to have
this functionality in Maxima.  Does anybody know if this code is still
around somewhere, and if so, if it can be (easily) ported to Maxima?

Thanks,
Alasdair