Improving Information Retrieval System Security via an Optimal Maximal Coding Scheme

Novel maximal coding compression techniques for the most important file-the text file of any full-text retrieval system are discussed in this paper. As a continuation of our previous work, we show that the optimal maximal coding schemes coincide with the optimal uniquely decodable coding schemes. An efficient algorithm generating an optimal maximal code (or an optimal uniquely decodable code) is also given. Similar to the Huffman codes, from the computational difficulty and the information-theoretic impossibility point of view, the problem of breaking an optimal maximal code is further investigated. Due to the Huffman code being a proper subclass of the optimal maximal code, which is good at applying to a large information retrieval system and consequently improving the system security