Paper 2024/559

Convolution-Friendly Image Compression with FHE

Axel Mertens, COSIC, KU Leuven
Georgio Nicolas, COSIC, KU Leuven
Sergi Rovira, Technology Innovation Institute (TII)
Abstract

During the past few decades, the field of image processing has grown to cradle hundreds of applications, many of which are outsourced to be computed on trusted remote servers. More recently, Fully Homomorphic Encryption (FHE) has grown in parallel as a powerful tool enabling computation on encrypted data, and transitively on untrusted servers. As a result, new FHE-supported applications have emerged, but not all have reached practicality due to hardware, bandwidth or mathematical constraints inherent to FHE. One example is processing encrypted images, where practicality is closely related to bandwidth availability. In this paper, we propose and implement a novel technique for FHE-based image compression and decompression. Our technique is a stepping stone towards practicality of encrypted image-processing and applications such as private inference, object recognition, satellite-image searching or video editing. Inspired by the JPEG standard, and with new FHE-friendly compression/decompression algorithms, our technique allows a client to compress and encrypt images before sending them to a server, greatly reducing the required bandwidth. The server homomorphically decompresses a ciphertext to obtain an encrypted image to which generic pixel-wise processing or convolutional filters can be applied. To reduce the round-trip bandwidth requirement, we also propose a method for server-side post-processing compression. Using our pipeline, we demonstrate that a high-definition grayscale image () can be homomorphically decompressed, processed and re-compressed in s with a compression ratio of 100/34.4 on a standard personal computer without compromising on fidelity.

Metadata
Available format(s)
PDF
Category
Applications
Publication info
Preprint.
Keywords
Fully Homomorphic EncryptionImage ProcessingImage CompressionCKKS
Contact author(s)
axel mertens @ esat kuleuven be
georgio nicolas @ esat kuleuven be
sergi rovira @ tii edu
History
2025-05-12: last of 3 revisions
2024-04-11: received
See all versions
Short URL
https://ia.cr/2024/559
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2024/559,
      author = {Axel Mertens and Georgio Nicolas and Sergi Rovira},
      title = {Convolution-Friendly Image Compression with {FHE}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2024/559},
      year = {2024},
      url = {https://eprint.iacr.org/2024/559}
}
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