Dipartimento di Ingegneria informatica, automatica e gestionale

We illustrate a general technique to construct towers of fields producing high order elements in Fq2n, for odd q, and in F22·3n, for n≥ 1. These towers are obtained recursively by xn2+xn=v(xn-1), for odd q, or xn3+xn=v(xn-1), for q= 2 , where v(x) is a polynomial of small degree over the prime field Fq and xn belongs to the finite field extension Fq2n, for an odd q, or to F22·3n. Several examples are provided to show the numerical efficacy of our method. Using the techniques of Burkhart et al. (Des Codes Cryptogr 51(3):301–314, 2009) we prove similar lower bounds on the orders of the groups generated by xn, or by the discriminant δn of the polynomial. We also provide a general framework which can be used to produce many different examples, with the numerical performance of our best examples being slightly better than in the cases analyzed in Burkhart et al. (2009).