Cryptanalysis of indistinguishability obfuscation using GGH13 without ideals
Recently, Albrecht, Davidson and Larraia described a variant of the GGH13 without ideals and presented the distinguishing attacks in simplified branching program security model. Their result partially demonstrates that there seems to be a structural defect in the GGH13 encoding that is not related to the ideal 〈g〉. However, it is not clear whether a variant of the CGH attack described by Chen, Gentry and Halevi can be used to break a branching program obfuscator instantiated by GGH13 without ideals. Consequently this is left as an open problem by Albrecht, Davidson and Larraia. In this paper, we describe a variant of the CGH attack which breaks the branching program obfuscator using GGH13 without ideals. To achieve this goal, we introduce matrix approximate eigenvalues and build a relationship between the determinant and the rank of a matrix with noise. Our result further strengthens the work of Albrecht, Davidson and Larraia that there is a structural weakness in ‘GGH13-type’ encodings beyond the presence of 〈g〉.