Public-Key Encryption With Fuzzy Keyword Search Withstanding Keyword Guessing Attacks
With tremendous interests having been attracted, Public-key Encryption with Keyword Search (PEKS) achieves the searchability of public-key encrypted keywords. However, nearly all existing PEKS schemes and the expansions obtain their provable security under an implicit condition that the size of the keyword space is beyond the polynomial level, which shows inefficiency in practice. Hence, these existing schemes are insecure under keyword guessing attacks in applications. As the authors observe, the key to defend such attacks is to avoid the availability of the exact keyword trapdoor to adversaries. Accordingly, they compromise the exactness of keyword trapdoor by mapping at least two different keywords into a common fuzzy keyword trapdoor.