ice, the host will use Bluetooth to scan whether the device is online. If the user takes the device away from the host Bluetooth communication range , the computer will automatically lock screen. After mobile device and the host re-establish a Bluetooth connection, user needs to enter the 6 digit OTP code which will be displayed on the mobile device, to complete the authentication.
The terminal uses Android file API to read SD card. After enters the password, the user can use the 256 bits AES block cipher to encrypt files and send the encrypted files through Bluetooth, Wi-Fi or email to other devices. We use JCA, network programming and multithreading in the keys exchange and secret multimedia communication. First, the host and terminal establish session keys using Diffie-Hellman key exchange protocol. Then the terminal will send the audio and video streams which are encrypted via 256 bit AES block cipher to the host in UDP packages. The host can play the received media file or forward it to the other devices.
The work achieves Android-based hand-held authentication and multimedia secure communication, it can protect critical data and user privacy against viruses and hacker attacks, which improves security of computer system.
Key words: Android, identity authentication, secure communication, Diffie-Hellman key exchange protocol, AES block cipher, Java programming
摘　要 3
Abstract 4
第1章 作品介绍 7
　　1.1 背景分析 7
　　1.2 作品特色 7
　　1.3 相关工作 8
　　1.4 应用市场分析 8
第2章 实现方案 9
　　2.1 技术背景 9
　　　　2.1.1 为何选择JAVA语言 9
　　　　2.1.2 Android操作系统 10
　　　　2.1.3 Netbeans和Eclipse开发平台 10
　　　　2.1.4加密系统 11
　　　　2.1.5动态口令技术 15
　　2.2 实现原理 16
　　　　2.2.1 Diffie-Hellman密钥交换协议原理 16
　　　　2.2.2 AES加密原理 17
　　　　2.2.3 一次性口令原理 18
　　2.3 系统方案及软件流程 20
　　　　2.3.1 蓝牙设备绑定与搜索 20
　　　　2.3.2 路由表的