Directly performing operations on compressed data has been proven to be a big success facing Big Data problems in modern data management systems. These systems have demonstrated significant compression benefits and performance improvement for data analytics applications. However, current systems only focus on data queries, while a complete Big Data system must support both data query and data manipulation. To solve this problem, we develop CompressDB, which is a new storage engine that can support data processing for databases without decompression. CompressDB has the following advantages. First, CompressDB utilizes context-free grammar to compress data, and supports both data query and data manipulation. Second, for adaptability, we integrate CompressDB to file systems so that a wide range of databases can directly use CompressDB without any change. Third, we enable operation pushdown to storage so that we can perform data query and manipulation in storage systems without bringing large data to memory for high efficiency. We validate the efficacy of CompressDB supporting various kinds of database systems, including SQLite, MySQL, LevelDB, MongoDB, ClickHouse, and Neo4j. We evaluate our method using seven real-world datasets with various lengths, structures, and content in both single node and cluster environments. Experiments show that CompressDB achieves 40% throughput improvement and 44% latency reduction, along with 1.75 compression ratio on average.

Mobile agent and its security are first introduced in this paper. Fundamental to the mentioned communication security properties are issues relating to the identification and authentication of sending and receiving parties. A security authentication scheme for mobile agent of multi domain is provided and a detail description is given in the paper. The scheme is based on identity-based public key cryptography, so as to overcome some shortage posed by traditional authentication model based on PKI. The security of the scheme is also analyzed and it shows that the proposed scheme is secure and effective.

In order to improve the accuracy of trust evaluation of subscribers (or key holders) from relying parties' point of view, a new model of trust degrees for PKI is proposed. By analyzing the security risks during the applying and using process of certificates and private keys, we introduce non-trust factor (NTF); then based on NTF, a method for trust degrees of keys is presented. Comparing with the existing work, the model integrates several critical factors which influence trust degrees of keys into one formula, thus improving the accuracy of trust evaluation for PKI and being applicable to a variety of PKI trust models.

An efficient scheme of wavelength reuse is presented for solving the capacity limitation of WDM star single-hop networks by limited wavelengths. According to this scheme, the nodes supported by the network can be at least doubled under limited wavelength numbers. Under the same number of nodes, the delay of network can be greatly lowered, the throughput of the network can be increased 1–3 times, and the properties of the network can be efficiently improved.