I am reading this paper Toward Secure Multikeyword Top-k Retrieval over Encrypted Cloud Data.
I am trying to work out an example of the FHEI (Fully homomorphic Encryption over Integers) scheme mentioned on the paper, but unable to prove it. Can anyone explain the scheme with a working example?
Edit 1: I am unable to understand how to choose value of $r$ for equation $(pq + r)$. I am getting expected solution when using $r = 0$, but any other value of $r$ in range of ($-2^ρ, 2^ρ$) gives incorrect solution.