Parallel Search On Ciphertext Based On Index In Cloud Computing

With the development of information technology,the scale of data is growing during the people's daily life.Big data and cloud computing technology become a hot area.Nowadays more and more individuals and companies tend to sotre their data in cloud by a new service model called “data as a service”(DaaS),however,the open environment of cloud leads to some safety issues.Encryption is used to protect customers' privacy,especially in the open system,but it makes retrievaling encrypted data a problem.In veiw of some low performance of the existing SSE-1 scheme,this thesis uses different encryption strategies based on AES to design a crypt inverted index(Crypt-Lucene)that ensures the searchability of ciphertext,and then realizes the Crypt-Lucene algorithm.Its security is also analyzed.Additionally,a scheme for building Crypt-Lucene parallelly is proposed base on MapReduce,and this thesis also proposes how to search and update index parallelly in detail.Finally,the performance of Crypt-Lucene algorithm and parallel algorithm is analyzed in theory.Theoretical analysis and experiments are conducted to demonstrate the searchability and efficiency of the scheme.The experimental results show that it can reduce about 60% time to build index with Crypt-Lucene compared with SSE-1.It gets a higher and smoother search performance than SSE-1,and crypt index just grow 14% than lucene index.It is observed that building 8 Crypt-Lucene for large document collections with MapReduce on the Hadoop cluster consisting of four nodes can reduce 84.3% time,and can achieve the theoretical speed n(n is the number of index)approximatively.