Design And Implementation Of New White-Box Block Cipher Algorithm

Traditional cryptographic schemes are studied under the black-box model,which assumes that the encryption and decryption algorithm run on a trustworthy communication terminal,and the attacker can only access the input/output of the algorithm.However,as the Internet grew in popularity,the black-box model began to appear inadequate,the white-box model was put forward,under which the attacker has entire access to the implementation of the cryptographic algorithm and complete control over its execution environment.The research on the secure cryptographic primitives and implementation under the white-box model is called white-box cryptography.As a viable option,white-box cryptography can provide high security protection for applications such as digital rights management,mobile payments,wireless sensor networks,and others.In recent years,white-box cryptography has achieved many achievements in the respect of research.However,most white-box cryptography schemes currently have issues like high storage costs and insufficient security analysis.In this thesis,the design and analysis of white-box cryptography are studied in-depth,and the following contributions are obtained.Firstly,a white-box block cipher SPN-AS is proposed,which fulfills provable security and surpasses the existing schemes in storage cost.This design utilizes the AS iterative structure to construct a look-up table with a five-layer ASASA structure.A maximum distance separable matrix is employed as a linear layer to achieve full diffusion in a small number of rounds.Under the black-box model,SPN-AS can effectively prevent the attacker from recovering the key.The look-up table’s nonlinear layer S and affine layer A are both 16-bit,which can effectively avoid the decomposition attack against the ASASA structure and has the security against key extraction under the white-box model.Besides,SPN-AS possesses weak white-box(32KB,112)-space hardness in the respect of the security against code lifting.Secondly,a white-box block cipher WBSM4-LIKE is proposed to address the limitations of the existing white-box implementation schemes of the SM4 algorithm,such as a large memory footprint and low operational efficiency.The 8-bit random permutation generated by pseudorandom number generator and random permutation generation algorithm is used as the look-up table.It also reduces memory space and improves efficiency.The key extraction resistance under the white-box model is reduced to the security of AES-CTR under the black-box model.WBSM4-LIKE achieves key recovery resistance under the black-box model,which can effectively prevent the attacker from recovering the key,including the master key,and encryption/decryption key.Besides,the space hardness under the adaptively chosen space attack is selected to measure the resistance against code lifting,which is weak white-box(8KB,119)-space hardness.Finally,WBSM4-LIKE is implemented in Java language,and the correctness of the encryption and decryption algorithm and their efficiency are tested.The SM4 algorithm and Bai-Wu SM4 white-box scheme are respectively implemented in Java language to test their encryption efficiency.Compared with Bai-Wu SM4 white-box scheme,the look-up tables generation efficiency of our scheme is improved by about 173 times,and the encryption efficiency of the algorithm is improved by about 39 times.