BlindFilter: Privacy-Preserving Spam Email Detection Using Homomorphic Encryption.

Dongwon Lee, Myeonghwan Ahn, Hyesun Kwak, Jin B. Hong, Hyoungshick Kim

Research output: Chapter in Book/Conference paperConference paperpeer-review

1 Citation (Scopus)


Spam filtering services typically operate via cloud outsourcing, which exposes sensitive and private email content to the cloud server spam filter. Homomorphic encryption (HE) can address this issue by ensuring that user emails remain encrypted throughout all stages of the spam detection process on the cloud server. However, existing HE-based approaches are computationally infeasible due to the nature of HE operations. This paper proposes BlindFilter, a distributed, lightweight, HE-based spam email detection approach that consists of clients and servers collaborating to perform spam detection operations securely. BlindFilter employs WordPiece encoding and a modified Naive Bayes classifier, mitigating the need for multiplications and comparisons that would be prohibitive in terms of computation when applied with HE. Our experimental results demonstrate the efficacy of BlindFilter, with F1 scores exceeding 97% across two public email datasets. Furthermore, BlindFilter proves to be efficient as it can process an email in an average of 482.78 milliseconds. Our analysis also reveals that BlindFilter is robust against model extraction attacks, in which malicious users attempt to deduce the features of BlindFilter from query-response pairs.
Original languageEnglish
Title of host publicationProceedings 42nd International Symposium on Reliable Distributed Systems (SRDS 2023)
EditorsJuan E. Guerrero
PublisherIEEE, Institute of Electrical and Electronics Engineers
Number of pages11
ISBN (Electronic)9798350329100
ISBN (Print)979-8-3503-2910-0
Publication statusPublished - 2023
Event42nd International Symposium on Reliable Distributed Systems (SRDS) - Marrakesh, Morocco
Duration: 25 Sept 202329 Sept 2023

Publication series

NameProceedings of the IEEE Symposium on Reliable Distributed Systems
ISSN (Print)1060-9857


Conference42nd International Symposium on Reliable Distributed Systems (SRDS)
Abbreviated titleSRDS 2023


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