Proofs of retrievability (PoR) are probabilistic protocols which ensure that a client can recover a file he previously stored on a server. Good PoRs aim at reaching an efficient tradeoff between communication complexity and storage overhead, and should be usable an unlimited number of times. We present a new unbounded-use PoR construction based on a class of locally decodable codes, namely the lifted codes of Guo et. al.. Our protocols feature sublinear communication complexity and very low storage overhead. Moreover, the various parameters can be tuned so as to minimize the communication complexity (resp. the storage overhead) according to the setting of concern.

We here provide a method for systematic encoding of the Multiplicity codes introduced by Kopparty, Saraf and Yekhanin in 2011. The construction is built on an idea of Kopparty. We properly define information sets for these codes and give detailed proofs of the validity of Kopparty's construction, that use generating functions. We also give a complexity estimate of the associated encoding algorithm.

We discuss parameters of Goppa (1970) codes, such as minimum distance, covering radius, distance distribution, and generalized Hamming weights. By a variation on the exponential sums method and combinatorial arguments, we sharpen known bounds on these parameters.

We consider primitive cyclic codes of length p/sup m/-1 over F/sub p/. The codes of interest here are duals of BCH codes. For these codes, a lower bound on their minimum distance can be found via the adaptation of the Weil bound to cyclic codes. However, this bound is of no significance for roughly half of these codes. We shall fill this gap by giving, in the first part of the correspondence, a lower bound for an infinite class of duals of BCH codes. Since this family is a filtration of the duals of BCH codes, the bound obtained for it induces a bound for all duals. In the second part we present a lower bound obtained by implementing an algorithmic method due to Massey and Schaub (1988)-the rank-bounding algorithm. The numerical results are surprisingly higher than all previously known bounds.

New lower bounds on the minimum length of t-error-correcting BCH codes with covering radius at most 2t are derived.