Broadcast Encryption Scheme Based On Combinatorial Designs

A broadcast encryption scheme is a cryptosystem for sending messages to severalrecipients using an unsecured channel. According to requirements, the broadcastersends cipher texts such that only the privileged users can decrypt them. However,unauthorized users can’t read the cipher text. This new transmission withone-point-to-multipoint is provided with independency, security and secrecy. With therapid development and wide applications of computer network, broadcastingencryption meets the requirements in many application fields, such as premium cabletelevision, online database, satellite TV and other multimedia business digitalcopyright protection.In this paper, the development process and the research status of broadcastencryption are summarized firstly. According to the idea of Stinson[3], we usecombinatorial designs to achieve broadcasting encryption scheme. The following arethe main research:1、Analysised the broadcast encryption schemes based on balanced incomplete blockdesign (BIBD) and pointed out that schemes based on strong partly balancedincomplete block design (SPBIBD) which is weakerthan BIDB, have betterperformances.2、Introduced orthogonal array，perpendicular array and rational normal curve toconstruct the (SP)BIBD, established broadcast encryption scheme based on kindsof combinatorial structures, and analyzed the performances. Concluded that theupper bound of the number of collusion-resistant.3、Used dual design to improve the original schemes optimizing broadcast informationrate.4、Compared and analysised the performances of schemes with the same parameters.Concluded that the advantages and disadvantages of various solutions.5、Given the join of new members, a method of "reserve block" ensured that the keysof old members remain the same, but the public key for blocks can automatic updated.