  Private information retrieval (PIR) gets renewed attentions due to its
information-theoretic reformulation and its application in distributed storage
system (DSS). The general PIR model considers a coded database containing $N$
servers storing $M$ files. Each file is stored independently via the same
arbitrary $(N,K)$-MDS code. A user wants to retrieve a specific file from the
database privately against an arbitrary set of $T$ colluding servers. A key
problem is to analyze the PIR capacity, defined as the maximal number of bits
privately retrieved per one downloaded bit. Several extensions for the general
model appear by bringing in various additional constraints. In this paper, we
propose a general PIR scheme for several variant PIR models including: PIR with
robust servers, PIR with Byzantine servers, the multi-file PIR model and PIR
with arbitrary collusion patterns.
