Paper 2023/1291

On the Invalidity of LV16/Lin17 Obfuscation Schemes Revisited

Abstract

LV16/Lin17 IO schemes are famous progresses towards simplifying obfuscation mechanism. In fact, these two schemes only constructed two compact functional encryption (CFE) algorithms, while other things were taken to the AJ15 IO frame or BV15 IO frame. CFE algorithms are inserted into the AJ15 IO frame or BV15 IO frame to form a complete IO scheme. We stated the invalidity of LV16/Lin17 IO schemes. More detailedly, under reasonable assumption “real white box (RWB)” LV16/Lin17 CFE algorithms being inserted into AJ15 IO frame are insecure. In this paper, we continue to state the invalidity of LV16/Lin17 IO schemes. The conclusion of this paper is that LV16/Lin17 CFE algorithms being inserted into BV15 IO frame are insecure. The reasoning of this paper is composed of the following three steps. First, when LV16/Lin17 CFE algorithms are inserted into secret constants. Second, when all secret random numbers are changed into the BV15 IO frame, all secret random numbers must be changed into secret constants, component functions in LV16/Lin17 CFE algorithms are cryptologic weak functions, and shapes of these component functions can be easily obtained by chosen values of independent variables. Finally, the shapes of these component functions include parameters of original function, therefore the IO scheme is insecure.