主動式RFID的定位機制與輕量加密方法之研究

A study on positioning mechanism and light-weight cryptography on active RFID systems

王錫文(Hsi-Wen Wang)

指導教授 ： 李仁貴

國立臺北科技大學/電資學院/電腦與通訊研究所/博士(2013年)

https://doi.org/10.6841/NTUT.2013.00388

摘要

本研究分成二個部份，第一個部份為利用主動式無線射頻辨識的標籤與讀取器建立一個室內定位系統；第二個部份為主動式無線射頻辨識系統的加密認證系統。
第一個部份使用主動式無線射頻標籤的特性，建立一個二維平面的定位機制。使用矩型分佈的參考標籤做為收集目標標籤信標訊號的訊號接收強度指標。系統透過讀取器收集參考標籤接收到的訊號強度資訊後，利用定位演算法對目標標籤的位置進行估算。利用訊號接收強度指標做為距離量測的工具時，因電波在空間中傳遞時會受到地理環境的影響，使得系統在進行位置量的精確度有一定影響。在定位效能測試時，使用不同的參考標籤的分佈密度，以求測試出不同參考標籤間隔時對於定位效能的影響。由實驗測試的結果顯示，本研究使用的定位方式，在參考標籤間隔10公尺的矩型分布的狀況下，90%的區域定位誤差在3.34公尺以下。
第二部份使用馴變換公開金鑰做為加密機制，馴變換簽章具備高速生成金鑰的特性，以及適合微處理器實做的特性，再配合改良式授權機制，以及隨機挑戰碼，實現一個主動式標籤的無線射頻辨識系統。該系統具備不被追縱的特性與讀取器使用無線多跳界接後端伺服器，這樣的通訊方式可以增加系統佈置的彈性與便利性。

關鍵字

主動式無線射頻辨識 ； 室內定位 ； 輕量加密 ； 馴變換 ； 公開金鑰

並列摘要

This study includes two parts: one is to implement and experiment an indoor positioning system based on an active Radio Frequency Identification (RFID) system, and the other is an authentication protocol with light weight cryptography implemented in an active RFID system.
The first part of this study is mainly to implement an active RFID system for an indoor positioning service. The indoor positioning system uses four reference tags for the reference addresses and a tracked object equipped with an active tag. Reference tags transmit the received signal strength indicator (RSSI) and the unique electronic product code (EPC) back to the reader through wireless transmission. Then the back-end system employs the information which is received from the reference tags to determine the location of the tracked object by computing the geometric relation between the reference tags and the tracked object. Due to the radio signal being vulnerable to the interferences from the terrain and obstacles while propagating, readers are likely to receive signals with bad quality. This drawback can decrease the positioning accuracy. Therefore, this study sorts out several issues that could affect the positioning accuracy and probes into the influence degree of distance errors via the experiment. The results show that the distance error within 3.34 m is as high as 90% of total estimated positions in a 10 m × 10 m region where four coordinate references are arranged.
Beside location function, RFID systems need to face users concerns for privacy issues. Improving the security and privacy of RFID system is only the way to solve this issue. Encrypted information passed between tags and readers can avoid the attacker getting the information of tags, but it still cannot avoid adversary tracking tags by radio fingerprint. To prevent tracking attack, mutual authentication must be employed in the process of communication between tags and readers.
The second part of this study integrates an authentication mechanism with public key encryption, embedded computation, and wireless communication technologies into an active RFID system. In the active RFID system, a secure RFID tag intermittently transmits cipher text to a RFID reader which then transmits in multi-hop relaying to a back-end platform to perform data comparison for authentication. Tame Transformation Signatures (TTS) is used in the system to protect the plain text from adversaries. The TTS algorithm is from the family of asymmetric public key systems, and it has the advantages of high security, high-speed key generation, signature, and suitability to embedded systems and is thus suitable to be used in our authentication system. Therefore, TTS has superiority such as better security, fast key generation, complex algorithm, and low signature delay. TTS algorithm can perform authentication more effectively in the active RFID system. There are three major contributions in the second part of this study. The first is a fully designed and implemented an active RFID system, which includes active tags and readers. In the RFID system, tags can stand by and keep working in long term after getting started. The second is a successfully implemented active RFID system with TTS cryptography and authentication mechanisms to protect the content in tags to ensure the security in multi-hop transmission. The last is adopting multi-hop relays to extend distance between Readers.

並列關鍵字

Active RFID ； Indoor positioning ； Tame Transformation Signatures (TTS) ； Public key

參考文獻

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