Cryptology ePrint Archive: Report 2019/295

Balancing Image Privacy and Usability with Thumbnail-Preserving Encryption

Kimia Tajik and Akshith Gunasekaran and Rhea Dutta and Brandon Ellis and Rakesh B. Bobba and Mike Rosulek and Charles V. Wright and Wu-chi Feng

Abstract: In this paper, we motivate the need for image encryption techniques that preserve certain visual features in images and hide all other information, to balance privacy and usability in the context of cloud-based image storage services. In particular, we introduce the concept of ideal or exact Thumbnail-Preserving Encryption (TPE), a special case of format-preserving encryption, and present a concrete construction. In TPE, a ciphertext is itself an image that has the same thumbnail as the plaintext (unencrypted) image, but that provably leaks nothing about the plaintext beyond its thumbnail. We provide a formal security analysis for the construction, and a prototype implementation to demonstrate compatibility with existing services. We also study the ability of users to distinguish between thumbnail images preserved by TPE. Our findings indicate that TPE is an efficient and promising approach to balance usability and privacy concerns for images. Our code and a demo are available at

Category / Keywords: applications / Thumbnail-preserving image encryption, Format-preserving encryption, Image privacy, Usability

Original Publication (with minor differences): NDSS 2019

Date: received 14 Mar 2019

Contact author: tajikk at oregonstate edu

Available format(s): PDF | BibTeX Citation

Version: 20190320:102436 (All versions of this report)

Short URL:

[ Cryptology ePrint archive ]