| Summary: | Chen et al. indicated the inner keyword guessing attack coming from the low entropy of keywords, which eliminates the semantic security of most keyword search schemes. Then, they accordingly propose the first dual-server PEKS scheme (abbreviated as DS-PEKS) and its related security models to prevent such attacks. In the DS-PEKS architecture, two non-collusive servers must corporate to execute the keyword search procedure. No individual server has the capability of determining the equivalence between keywords alone, and thus the inner keyword guessing attacks can be avoided. In this article, we found that the security models are lack of soundness and strength, so our first result is to define new stronger and sounder security models which implies all security aspects of original models. Secondly, we also propose a generic construction of DS-PEKS schemes based on IND-CCA2 secure PKE schemes. Finally, we analyze the newly proposed DS-PEKS scheme, and proof its security with the stronger models based on the IND-CCA2 security in the standard model.
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