資訊安全的議題已經受到愈來愈多的重視，並且成為在設計資訊 系統時之一項重要考量。由於智慧卡之可攜性與防偽性，智慧卡可有 多種應用。然而，近年來學者提出之物理攻擊法，可藉由觀測防偽性 裝置於進行計算時，所產生之物理特徵值，來推測與破解密碼系統。 因此，倘若密碼系統之實作未能多此層面之考量，仍極有可能被物理 攻擊法所破解。 物理攻擊法的其中一類為能量攻擊法，本論文提出兩種防禦對 策，用以防禦此種能量攻擊法，期能增加智慧卡之安全性。第二章將 介紹於物理攻擊法中，最常被探討之能量攻擊法。第三章回顧能量攻 擊法之防禦對策。 在第四章中，本論文提出非確定式軟體技術，作為一種防禦能量 攻擊法之對策。我們運用程式軟體穿插交錯實作技巧，與非確定性之 程式執行方式，促使防偽性裝置於進行計算時，所產生之物理特徵值 呈現不規則之狀態，經由實驗證實，非確定式軟體技術之應用，可促 使能量攻擊法於執行時所需要收集之能量消耗波形數量增加，進而達 到使能量攻擊法更形困難之目標。 第五章提出遮罩分割對策。我們根據秘密分享之觀念，引入遮罩 分割技術，加強之前學者所提出的布林遮罩轉換算術遮罩機制，用更 為複雜的方式遮蔽原來能量消耗波形之物理特徵值，為使能量攻擊法 之實行更加繁瑣困難。並且，經由實驗證實，應用遮罩分割技術，確 可成功達到防制能量攻擊法之效果。 The issue of information security has attracted more and more attention, and usually is considered a major factor in the design of an information system. Being portable and tamperproof, a smart card can be used to provide additional services. However, physical cryptanalysis proposed recently intuitively observes physical characteristics leaked from an assumed tamperproof device such as a smart card. Therefore, when a cryptosystem is implemented without sufficient care, it may be vulnerable to physical cryptanalysis. In this thesis, we propose two countermeasures, non-deterministic software and the mask splitting technique, for the sake of strengthening the security of a smart card. Chapter 2 gives a short introduction on power analysis, that is most used and investigated. In chapter 3 we review some of the countermeasures used to prevent such attack. Chapter 4 proposes a non-deterministic software (NDS) technique as a countermeasure against DPA that utilizes the interleaving technique of software implementation for the sake of removing any correlation between power traces in the software according to non-deterministically executive operations. Chapter 5 investigates the mask splitting method (MSM) that is regarded as an improved mechanism of transformation from boolean mask to arithmetic mask. Detailed security analysis of mask splitting applied is also discussed.
