利用錯誤更正碼提升RFID PUF識別可靠度之研究

Abstract

無線射頻辨識技術(Radio Frequency Identification, 簡稱RFID)中如何產生一個獨一無二而無法被攻擊者破解的ID，一直以來都是很困擾大家的問題。傳統RFID的做法，是透過金鑰加密的方式將所要傳遞的訊息進行加密的保護動作，使得攻擊方無法輕易的破解傳遞的訊息。這種做法卻對安全性有很大的缺點，攻擊者可以輕易的透過各種攻擊方式，取得ID或偽造標籤進而做出竊取個人資料與侵害隱私權的行為，這對個人的財產安全與個人資訊的保護有著很大的威脅。 物理不可複製函數(Physical Unclonable function,簡稱PUF)是一個被具體化的物理結構函數，它是半導體安全中最新的認證技術之一，其主要是透過製造矽晶片時，由於製程會產生有限度的漂移，使得每個晶片具有的物理特性有所不同，藉由此特性來創造出該晶片的DNA數碼，我們將利用PUF技術產生之數碼應用於RFID系統上，這方法可以避免攻擊者能夠輕易的竊取、竄改與偽造標籤的動作。由於矽晶片是對環境因素很敏感的元件，當溫度跟工作電壓的變化會造成PUF的特性改變使得原本正確的數碼也產生錯誤，造成應用於RFID系統時容易造成身份識別錯誤的問題。 本論文針對工作電壓跟溫度改變的時候，如何利用錯誤修正碼來修補PUF因為環境變數而造成的錯誤位元，使得讀取器要求標籤傳送資訊的時候，PUF能夠傳送出正確的資訊來提高PUF應用於RFID系統的可靠度。同時，我們在本篇論文也提出了一個新型的PUF架構，主要利用相同製程上的漂移，造成每個晶片的導線與元件特性的差異，使得電路動作時會產生時間的變化，計算出這個變化量並量化該變化量形成數碼，然後再利用錯誤更正碼(Error Control Coding)產生檢查碼，並且利用檢查碼，更正PUF因為環境因素造成的錯誤位元問題，進而減少整筆訊息的封包錯誤率(Package Error Rate)，提高整個系統的可靠度。

In radio frequency identification (RFID) field, it’s a tough problem to generate a unique ID which is hard to be cracked. Traditionally, the delivered message is protected and encrypted by key-cryptography to make sure it cannot be cracked easily. However, there is security vulnerability that the attacker can obtain IDs or counterfeit tags easily to infringe the right of privacy by any means of attacks. It threatens largely not only personal information but also property safety. Physical Unclonable function (PUF) is specific physical structure function. It’s one of the novel techniques of identity authentication. Each chip has own DNA serial digits which is defined by the different physical characteristics due to the limited drift during the manufacture of silicon wafer. The digits generated by PUF technique was applied on RFID system, this method avoids the tag being stolen, tampered and counterfeited by attacker. Silicon devices are sensitive to environment, the variations of temperature and operating voltage would change the characteristics of PUF and generate incorrect digits, these result in the identification failure. In this thesis, the ECC was used to repair the error bits caused by the variations of temperature and operating voltage. ECC engine makes RFID tag can deliver correct information to the reader and increase the identification reliability for the PUF being used in RFID system. Meanwhile, a novel PUF architecture was proposed, it utilizes the drift of semiconductor process to have different characteristics of interconnects and devices and diverse timing performance in each chip. The proposed PUF circuit counts the delay variation to generate digits; the ECC engine processes the digits with the calculated parity to fix the erroneous bits. This method reduces the package error rate to the delivered message and increases the system reliability.