Design And Analysis Of Stream Ciphers Based On Grain-Like Algorithm Structure

As a mainstream message encryption method,stream cipher has the advantages of simple implementation and fast encryption operations,and thus it is often suitable for secret communication in resource-constrained environments.To resist Time-Memory-Data Tradeoff(TMDTO)attacks,the internal state length of stream cipher is usually selected to be twice the length of the secret key,which greatly limits their implementation and application in many resource-constrained environments.For instance,Grain v1 is a Feedback Shift Register(FSR)based cipher,which was proposed in the European e STREAM Streaming Cryptography Initiative.In particular,it is also one of the winning ciphers with the lowest hardware complexity and one of the most efficient implementations.However,Grain v1 has an internal state of 160 bits,a key length of 80 bits and some new security issues.How to design a lightweight stream cipher with a small internal state that can resist TMDTO attacks is a key research topic in the industry.In addition,designing a highly secure stream cipher algorithm is also a challenging research task.In thesis,two new stream ciphers based on Grain LFSR and NFSR are designed,and security is evaluated.The main research result is given below:1.A small state lightweight stream cipher was designed,which uses non-volatile keys and initial vectors for continuous usage.A new small-state stream cipher,BLOOM,is designed to address the shortcomings of existing lightweight stream ciphers by incorporating the structure of Grain-like ciphers.The cipher has an internal state of 132 bits and a key length of 128 bits.The cipher component uses two NFSRs,and a non-volatile memory.In particular,the non-volatile memory contains a key prefix and an initial vector,which are involved in the initialization and keystream generation processes respectively by a selection function.The results show that the cipher can effectively resist TMDTO attacks and improve security while reducing hardware overhead.Compared with the Grain-128 a cipher,this new cipher is more suitable for applications in resource-constrained environments due to its reduced area and power consumption.2.The security of the BLOOM is analyzed.The randomness of BLOOM is first tested using the NIST sts-2＿1＿2 test package;subsequently,the ability of the BLOOM cipher to resist algebraic attacks,cubic attacks and sliding attacks is discussed.The results show that the BLOOM can pass the NIST randomness test with good pseudo-randomness;the cipher is sufficient to resist known stream cipher attack methods.3.A stream cipher called Grain-DL was designed based on NFSR and clock-controlled dual LFSR.Based on the structure of Grain-like ciphers,the stream cipher is designed using two linear feedback shift registers(LFSR)and one NFSR,and using a clock-controlled module to control the selection of the linear feedback shift registers.The cipher has an internal state of 288 bits,while the key length is 128 bits.The cipher uses separate LFSR selection methods in the initialization phase and the key generation phase,with the aim of increasing the complexity of the cipher analysis.Compared to existing Grain-like ciphers,Grain-DL uses two LFSRs clock-controlled design,which gives the cipher more complexity and robustness,allowing the initial vector and key to be sufficiently and rapidly confused and diffused.The Grain-DL can pass the randomness test.Moreover,it is enough to resist classical stream cryptography attacks such as algebraic attack,cubic attack and sliding attack.