The K-ryptography and Information Security for Open Networks research group is pleased to invite you to the Seminar «Joint Reversible Data Hiding and Homomorphic Encryption of Scalar Data» given by Prof. David Megías Jiménez, professor, co-director of KISON research group and director of the Ethical Technologies and Connectivity for Humanity Research Center (UOC-TECH) at the UOC.
The seminar will be held, on-site, on Thursday, November 20 at 11:30 am (CET) in room O2.13 of the building O.
Venue
Building O (room 02.13)
Rambla del Poblenou, 156
08018 Barcelona
Espanya
When
20/11/2025 11.30h
Organized by
Universitat Oberta de Catalunya, K-ryptography and Information Security for Open Networks research group
Program
Summary
This seminar addresses the challenge of securing data collected from IoT sensors, where readings are taken at discrete and often widely dispersed time intervals. In this environment, a sensor transmits its data to a Data Collector (DC), and the primary objective is to simultaneously ensure data integrity, data provenance, and confidentiality.
Classical reversible data hiding methods, such as Histogram Shifting, Difference Expansion, or Prediction Error Expansion, are not suitable for this scenario because they require multiple, closely-sampled data points. The challenge is to reversibly embed a watermark within a single scalar data value.
This work presents advancements in data security for IoT environments by introducing H[i]dden, a novel methodology for Joint Reversible Data Hiding and Homomorphic Encryption of scalar data. The initial proposal takes advantage of the complex domain, forming a Gaussian integer where data and watermark are stored in the real and imaginary parts, respectively. This combined data is intrinsically blended via complex multiplication with a secret key. Building on this, the H[i]dden-Exp framework is proposed, which applies the complex polar form. This design stores the scalar data in the phase and the watermark in the magnitude.
Both approaches enable operations in the encrypted domain by adopting a Gaussian Integer ElGamal Cryptosystem, which facilitates homomorphic multiplication for the Cartesian approach and leverages the same multiplicative homomorphism to perform addition (aggregation) in the exponent for the H[i]dden-Exp scheme.
Professor, co-director of KISON research group and director of the Ethical Technologies and Connectivity for Humanity Research Center (UOC-TECH) at the UOC. His current research focuses on information security and privacy, including security and privacy in multimedia content distribution (especially in areas such as watermarking and digital fingerprinting), steganography and stegananalysis, and privacy issues in different decentralized network applications. He has published more than 150 research papers in numerous international journals and conferences—49 in journals indexed by Journal Citation Reports (JCR)—and has participated in several joint nationals research projects as a collaborator and principal investigator. In addition, he has supervised six doctoral theses and is a member of the editorial board and program committees of several journals and conferences in the field of security and privacy.
This seminar is held under the ARTEMISA International Chair of Cybersecurity and the DANGER Strategic Project of Cybersecurity, both funded by the Spanish National Institute of Cybersecurity through the European Union's NextGenerationEU programme and the Recovery, Transformation and Resilience Plan.
