The Implementation Security Of Block Ciphers Against Side Channel Attacks Based On Memory System

As the most fundamental part of cryptosystem,the block cipher is also the cornerstone of modern information security,and its implementation security is subject to researches from both industry and academic.Block ciphers are generally implemented as cryptography libraries.By merging all commonly used ciphers to a single library,users can leverage the API provided by library to achieve the encryption,rather than writing a complex cipher program by themselves.However,during the encryption,the cipher would leave traces in the computer memory system,it leaks information that can be captured by the attacker,like time,power or electromagnetic radiation.So the attacker can deduce the internal state of encryption based on these leakages,and then reveal the cipher key.Such attack method is the so-called side channel attack.In recent years,with the increasing of people's awareness of security and the popularization of computers,more and more personal data and even the country sensitive secret are saved by encrypting with the block ciphers.And the existing of side channel attacks poses a great threat on these data.This thesis presents a thorough research on the side channel attacks,and evaluates the resistance of multiple advanced cryptography libraries,and also analyzes the implementation security of multiple typical block ciphers.The work details are shown below:1.Design a novel active side channel attack based on the Rowhammer bug,which is a famous memory vulnerability.It can inject faults to the s-box of cipher only with normal memory access,misleading the encryption in a predictable way,and finally reveals the master key by analyzing error ciphertexts.2.Combine the algebraic analysis with traditional cache attacks,proposing a new algebraic cache attack method,which also introduces the SAT solver to analyze and solve the key automatically.The method greatly decreases the attack complexity,the attacker is not required to have sophisticated knowledge,so that it is beneficial to toolize and generalize the method.3.Propose a novel differential cache attack,by introducing the statistic analysis,which achieves the fine-grained analysis of cache side channel leakages on the computer platform in the first time.And it also present a backward plaintext construction method,in which the attacker can crack the latest version of cryptography libraries in a few seconds based on these constructed plaintexts.4.Analyze all existing defenses for side channel attacks,and classify them into multiple classes.For each type of defense,the advantages and disadvantages are analyzed,and the future directions are predicted.Meanwhile,for three attack methods proposed in this paper,the possible countermeasures are also discussed.