Transmission-efficient broadcast encryption scheme with personalized messages

다국어 초록 (Multilingual Abstract)

Broadcast encryption scheme with personalized messages (BEPM) is a new primitive that allows a broadcaster to encrypt both a common message and individual messages. BEPM is necessary in applications where individual messages include information related to user’s privacy. Recently, Fujii et al. suggested a BEPM that is extended from a public key broadcast encryption(PKBE) scheme by Boneh, Gentry, and Waters.
In this thesis, the first result is a new BEPM that has O(|R|) transmissionefficiency, while preserving O(1) user storage cost. This construction is based on a PKBE scheme suggested by Park, Kim, Sung, and Lee, which is also considered as being one of the best PKBE schemes. It is pointed out that Conditional Access System using Fujii et al.’s BEPM should be modified in a way that decryption algorithm takes as input public key as well. It is showed that performance analysis should be done depending on whether the public key is transmitted along with ciphertext or stored into user’s device. It is considered that all user’s public key cannot be stored in each user’s device like a smartphone which has small storage capacity.
Secondly a grouping enabled BEPM is proposed. With this scheme a sender is able to send a certain message to subgroup of receivers. Given a constant u which is the number of subgroup, this grouping enabled BEPM is constructed with addition u elements to public key PK, private key di and header Hdr and this scheme still preserves O(|S|) transmission cost and O(1) user storage cost.
Thirdly, a fully secure BEPM is proposed for the first time using dual system encryption. This scheme is full-ID secure under the simple assumption. When the broadcasters want to send the individual information, they need more secure encryption system for protecting user’s privacy which becomes more important than before.

목차 (Table of Contents)

• Contents
• 1 Introduction
• 1.1 Overview
• 1.2 Motivations of this Thesis
• 1.3 Contributions of this Thesis
• 1.4 Related Works
• 2 Background
• 2.1 Broadcast Encryption with Personalized Messages(BEPM)
• 2.2 Security Model
• 2.2.1 Selective-ID Security Model
• 2.2.2 Full-ID Security Model
• 2.3 Bilinear Pairings
• 2.4 Complexity Assumption
• 2.4.1 The n-modified Bilinear Diffie-Hellman Assumption
• 2.4.2 Decisional Bilinear Diffie-Hellman Assumption
• 2.4.3 Decisional Linear Assumption
• 2.4.4 Decisional Bilinear Diffie-Hellman Exponent Assumption (BDHE)
• 3 Previous Works
• 3.1 Symmetric Key Broadcast Encryption
• 3.1.1 NNL’s Broadcast Encryption(BE)
• 3.2 Public Key Broadcast Encryption(PKBE)
• 3.2.1 BGW’s PKBE
• 3.2.2 PKSL’s PKBE
• 3.3 Fujii et al.’s BEPM
• 3.4 Waters’ Dual system
• 4 Generic BEPM
• 4.1 Generic BEPM
• 4.2 Security and Transmission Efficiency
• 5 Transmission-Efficient BEPM
• 5.1 Overview
• 5.2 Basic Scheme
• 5.2.1 Construction
• 5.2.2 Correctness
• 5.2.3 Security
• 5.3 General Scheme
• 5.3.1 Construction
• 5.3.2 Correctness
• 5.3.3 Security
• 5.4 Chosen Ciphertext Secure Scheme
• 5.4.1 Construction
• 5.4.2 Correctness
• 5.4.3 Security
• 5.5 Performance Analysis
• 5.5.1 Performance Comparison between Basic Scheme
• 5.5.2 Performance Comparison between General Schemes
• 5.5.3 Other Performance Issues about Pre-computation Scheme and using a Portable Device
• 5.6 The Decisional n-modified Bilinear Diffie-Hellman Problem in Generic Groups with Bilinear Maps
• 6 Grouping-Enabled BEPM
• 6.1 Overview
• 6.1.1 Definition of Grouping-Enabled BEPM
• 6.1.2 Security for Grouping-Enabled BEPM
• 6.2 Scheme
• 6.2.1 Construction
• 6.2.2 Correctness
• 6.2.3 Security
• 7 Fully Secure BEPM using Dual System
• 7.1 Overview
• 7.2 Scheme
• 7.2.1 Construction
• 7.2.2 Correctness
• 7.2.3 Semi-Functional Algorithms
• 7.3 Security Analysis
• 7.3.1 Distinguishment between GameReal and Game0
• 7.3.2 Distinguishment between GameK−1 and GameK
• 7.3.3 Distinguishment between GameN and GameFinal
• 8 Conclusions