Studies in Lightweight Cryptography

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Hadi Soleimany Name of the doctoral dissertation Studies in Lightweight Cryptography Publisher School of Science Unit Department of Information and Computer Science Series Aalto University publication series DOCTORAL DISSERTATIONS 211/2014 Field of research Theoretical Computer Science Manuscript submitted 26 September 2014 Date of the defence 30 January 2015 Permission to publish granted (date) 28 November 2014 Language English Monograph Article dissertation (summary + original articles) Abstract The decreasing size of devices is one of the most significant changes in telecommunication and information technologies. This change has been accompanied by a dramatic reduction in the cost of computing devices. The dawning era of ubiquitous computing has opened the door to extensive new applications. Ubiquitous computing has found its way into products thanks to the improvements in the underlying enabling technologies. Considerable developments in constraint devices such as RFID tags facilitate novel services and bring embedded computing devices to our everyday environments. The changes that lie ahead will eventually make pervasive computing devices an integral part of our world. The growing prevalence of pervasive computing devices has created a significant need for the consideration of security issues. However, security cannot be considered independently, but instead, should be evaluated alongside related issues such as performance and cost. In particular, there are several limitations facing the design of appropriate ciphers for extremely constrained environments. In response to this challenge, several lightweight ciphers have been designed during the last years. The purpose of this dissertation is to evaluate the security of the emerging lightweight block ciphers. This dissertation develops cryptanalytic methods for determining the exact security level of some inventive and unconventional lightweight block ciphers. The work studies zerocorrelation linear cryptanalysis by introducing the Matrix method to facilitate the finding of zero-correlation linear approximations. As applications, we perform zero-correlation cryptanalysis on the 22-round LBlock and TWINE. We also perform simulations on a small variant of LBlock and present the first experimental results to support the theoretical model of the multidimensional zero-correlation linear cryptanalysis method. In addition, we provide a new perspective on slide cryptanalysis and reflection cryptanalysis by extending previous research of self-similarity cryptanalysis. Unlike classical techniques, our approach is not limited to deterministic characteristics. To demonstrate the impact of our model we provide statistical and structural analysis of three well-known lightweight block ciphers: ITUbee, Zorro and LED. As a result of the analysis presented in this work new security criteria for PRINCElike ciphers are obtained.The decreasing size of devices is one of the most significant changes in telecommunication and information technologies. This change has been accompanied by a dramatic reduction in the cost of computing devices. The dawning era of ubiquitous computing has opened the door to extensive new applications. Ubiquitous computing has found its way into products thanks to the improvements in the underlying enabling technologies. Considerable developments in constraint devices such as RFID tags facilitate novel services and bring embedded computing devices to our everyday environments. The changes that lie ahead will eventually make pervasive computing devices an integral part of our world. The growing prevalence of pervasive computing devices has created a significant need for the consideration of security issues. However, security cannot be considered independently, but instead, should be evaluated alongside related issues such as performance and cost. In particular, there are several limitations facing the design of appropriate ciphers for extremely constrained environments. In response to this challenge, several lightweight ciphers have been designed during the last years. The purpose of this dissertation is to evaluate the security of the emerging lightweight block ciphers. This dissertation develops cryptanalytic methods for determining the exact security level of some inventive and unconventional lightweight block ciphers. The work studies zerocorrelation linear cryptanalysis by introducing the Matrix method to facilitate the finding of zero-correlation linear approximations. As applications, we perform zero-correlation cryptanalysis on the 22-round LBlock and TWINE. We also perform simulations on a small variant of LBlock and present the first experimental results to support the theoretical model of the multidimensional zero-correlation linear cryptanalysis method. In addition, we provide a new perspective on slide cryptanalysis and reflection cryptanalysis by extending previous research of self-similarity cryptanalysis. Unlike classical techniques, our approach is not limited to deterministic characteristics. To demonstrate the impact of our model we provide statistical and structural analysis of three well-known lightweight block ciphers: ITUbee, Zorro and LED. As a result of the analysis presented in this work new security criteria for PRINCElike ciphers are obtained.