A Note on "Confidentiality-Preserving Image Search: A Comparative Study   Between Homomorphic Encryption and Distance-Preserving Randomization"
  Recently, Lu et al. have proposed two image search schemes based on additive homomorphic encryption [IEEE Access, 2 (2014), 125-141]. We remark that both two schemes are flawed because: (1) the first scheme does not make use of the additive homomorphic property at all; (2) the additive homomorphic encryption in the second scheme is unnecessary and can be replaced by a more efficient symmetric key encryption. 
Zhengjun Cao and Lihua Liu
cs.CR