An important family of codes for data storage systems, cryptography, consumer electronics, and network coding for error control in digital communications are the so-called cyclic codes. This kind of linear codes are also important due to their efficient encoding and decoding algorithms. Because of this, cyclic codes have been studied for many years, however their complete weight distributions are known only for a few cases. The complete weight distribution has a wide range of applications in many research fields as the information it contains is of vital use in practical applications. Unfortunately, obtaining these distributions is in general a very hard problem that normally involves the evaluation of sophisticated exponential sums, which leaves this problem open for most of the cyclic codes. In this paper we determine, for any finite field IFq, the explicit factorization of any polynomial of the formxq+1-c, wherec∈ IFq*. Then we use this result to obtain, without the need to evaluate any kind of exponential sum, the complete weight distributions of a family of irreducible cyclic codes of dimension two over any finite field. As an application of our findings, we employ the complete weight distributions of some irreducible cyclic codes presented here to construct systematic authentication codes, showing that they are optimal or almost optimal.

Abstract A class of optimal three-weight $$[q^k-1,k+1,q^{k-1}(q-1)-1]$$ [ q k - 1 , k + 1 , q k - 1 ( q - 1 ) - 1 ] cyclic codes over $${\mathrm{I\!F}}_q$$ I F q , with $$k\ge 2$$ k ≥ 2 , achieving the Griesmer bound, was presented by Heng and Yue (IEEE Trans Inf Theory 62(8):4501–4513, 2016. https://doi.org/10.1109/TIT.2016.2550029). In this paper we study some of the subfield codes of this class of optimal cyclic codes when $$k=2$$ k = 2 . The weight distributions of the subfield codes are settled. It turns out that some of these codes are optimal and others have the best known parameters. The duals of the subfield codes are also investigated and found to be almost optimal with respect to the sphere-packing bound. In addition, the covering structure for the studied subfield codes is determined. Some of these codes are found to have the important property that any nonzero codeword is minimal, which is a desirable property that is useful in the design of a secret sharing scheme based on a linear code. Moreover, a specific example of a secret sharing scheme based on one of these subfield codes is given. Finally, a class of optimal two-weight linear codes over $${\mathrm{I\!F}}_q$$ I F q , achieving the Griesmer bound, whose duals are almost optimal with respect to the sphere-packing bound is presented. Through a different approach, this class of optimal two-weight linear codes was reported very recently by Heng (IEEE Trans Inf Theory 69(2):978–994, 2023. https://doi.org/10.1109/TIT.2022.3203380). Furthermore, it is shown that these optimal codes can be used to construct strongly regular graphs.