"PCSF: Privacy-Preserving Content-based Spam Filter" by Intae Kim, Willy Susilo et al.
The purpose of privacy-preserving spam filtering is to inspect email while preserving the privacy of its detection rules and the email content. Although many solutions have emerged, they suffer from the following: 1) The privacy provided is insufficient as the email content or detection rules may be exposed to third parties; 2) Due to improper use of encryption, exhaustive word search attacks are possible, potentially breaking the confidentiality of encrypted emails; 3) When spam filtering is outsourced, email is given to the outsource, where user privacy may be compromised if privacy protecti...
Source: uow.edu.au