Design And Analysis Of Lightweight Stream Ciphers In Internet Of Things Environment

As the third wave of information industry,the Internet of Things?IoT?is developing rapidly,but the data security of IoT devices is becoming more and more prominent.The research on IoT security has lagged behind the development of the IoT industry.Most of the devices in the sensing layer are micro-processors with limited storage capacity and computing power.Traditional cryptographic algorithms provide high-level cryptographic performance and do not consider resource environments.It makes them difficult to adapt to hardware-constrained devices.Designing lightweight ciphers for IoT devices has become a hot topic of research.Stream cipher has the characteristics of fast encryption and decryption speed,easy hardware implementation and so on.It is suitable as an encryption scheme for IoT devices.However,the birthday-bound security generated by Time-Memory-Data tradeoff?TMDTO?attacks has been restricting the lightweight of stream ciphers.In recent years,there have been several lightweight stream cipher structures that provide beyond-the-birthday-bound security against Time-Memory-Data tradeoff attacks.In this thesis,the parameter relationships of these lightweight stream cipher structures that can resist TMDTO attacks were derived.On this basis,we designed an ultra-lightweight stream cipher algorithm to protect the confidentiality of data transmitted by the low-frequency RFID tags.The main research work and innovation are as follows:Firstly,in order to improve the security of lightweight stream cipher structure against TMDTO attacks,we deduced the algorithm parameter relationship of the Continuous-Key-Use?CKU?structure,Lizard structure and Continuous-IV-Use?CIVU?structure to ensure 2^{K L} security under TMDTO attacks.The deduction results showed that the variable internal state length of the CKU structure should be greater than or equal to the key length?VSL?KL?,and the IV length should be greater than or equal to the key length?IVL?KL?.The internal state length of the Lizard structure should be more than twice the length of the key?SL?KL?.The CIVU structure should store both Key and IV,and the IV length should not be less than the key length?IVL?KL?.Finally,the practical constraints of TMDTO attacks were analyzed.Then,on the basis of TMDTO analysis,facing the practical constraints of low-frequency RFID tags,the ultra-lightweight stream cipher algorithm Willow was designed based on the CKU structure to ensure the confidentiality of data transmitted by RFID Tags.Willow uses a new dynamic initialization method to reduce the number of initialization rounds,thereby reducing latency and power.The new dynamic initialization can avoid the generation of weak Key/IV pairs.The set of tap is a positive difference set,so that the complexity of guess and determine attack is higher than the exhaustive attack.Willow can resist fast correlation attacks due to high correlation immunity.Finally,after the security analysis of the willow,the IC front-end simulation was performed on the current lightweight stream cipher and the NIST randomization test was performed on the willow.Firstly,Verilog coding and debugging of the lightweight stream cipher algorithms Sprout,Plantlet,Fruit-v2,Lizard and Willow were carried out by Vivado.Then,we used Modelsim to perform functional simulation of the cryptographic algorithm to verify the correctness of the coding.Finally,synthesis and optimization were carried out through the Design Compiler.The area,power consumption and latency of all algorithms were measured using the same design specifications and procedures.The simulation results verify that Willow has a better hardware performance than the existing lightweight stream cipher algorithm.Finally,a NIST randomization test was performed on keystream sequence of Willow.The test results showed that keystream sequence of Willow is random.