Shinnosuke Nozue, Yuto Nakano, Shoji Moriya, Tomoki Ariyama, Kazuma Kokuta, Suchun Xie, Kai Sato, Shusaku Sone, Ryohei Kamei, Reina Akama, Yuichiroh Matsubayashi, Keisuke Sakaguchi. Proceedings of the 25th Annual Meeting of the Special Interest Group on Discourse and Dialogue. 2024.

Threats and risks against supply chains are increasing and a framework to add the trustworthiness of supply chain has been considered. In this framework, organisations in the supply chain validate the conformance to the pre-defined requirements. The results of validations are linked each other to achieve the trustworthiness of the entire supply chain. In this paper, we further consider this framework for data supply chains. First, we implement the framework and evaluate the performance. The evaluation shows 500 digital evidences (logs) can be checked in 0.28 second. We also propose five methods to improve the performance as well as five new functionalities to improve usability. With these functionalities, the framework also supports maintaining the certificate chain.

The Internet of things (IoT) has come into widespread use, and data protection and integrity are critical for connected IoT devices in order to maintain security and privacy. Low-power wide-area (LPWA) technologies for IoT wireless communication achieve data protection and integrity by using encryption and message authentication. However, side-channel analysis techniques exist that have the capacity to recover secret information from a device. In this paper, we apply a side-channel analysis technique to the payload encryption process and message authentication code generation process on a real LoRaWAN end-device. The entire AES-128 key for the payload encryption can be recovered with 260 electromagnetic(EM)-leakage traces and 12 bytes of the key for message authentication code generation can be recovered with 140 EM-leakage traces.

When a user consumes an encrypted digital content (for example video and music files), the player application accesses the secret key to decrypt the content. If the user is malicious, he can analyse the access pattern of the player application to extract the secret key efficiently. Oblivious RAMs (ORAMs) are effective solution for such threats. However, ORAMs are only effective for `passive' attackers who can observe the RAM access done by the application, but cannot alter data stored on RAM. The attacker with ability to alter data on RAM can be called `active' attackers. In this paper, we evaluate the security of ORAM schemes against active adversaries where they alter data on RAM and try to efficiently extract the secret information. We also propose countermeasures against active adversaries.

Cloud services provide advantages in terms of service scalability and availability of users' data, but increase concerns about the control that a user has over her own data. These concerns include not just issues related to access to the information itself, but issues about the effective deletion of the information by the cloud in compliance with the user's right to deletion. In this on-going work, we present a mechanism that allows users to control access to and deletion of their information stored on the cloud. Our construction separates the user's content into several encoded pieces most of which are stored by a cloud provider. The remaining encoded pieces are stored by the user and are served directly from the user's infrastructure to the persons interested in viewing the content. The encoding must satisfy the property that without the pieces stored in the user's infrastructure none of the data is revealed. This property is found in several constructions related to secret sharing. We evaluate the practical feasibility of our proposal by developing an image sharing mechanism and simulating the user infrastructure using a single-board computer connected to the home Internet connection of one of the authors.

A proof of Data Possession (PDP) allows a client to verify that a remote server is still in possession of a file entrusted to it. One way to design a PDP, is to compute a function depending on a secret and the file. Then, during the verification stage, the client reveals the secret input to the server who recomputes the function and sends the output back to the client. The client can then compare both values to determine if the server is still in possession of the file. The problem with this approach is that once the server knows the secret, it is not useful anymore. In this article, we present two PDP schemes inspired in Multiple-Server Private Information Retrieval (MSPIR) protocols. In a traditional MSPIR protocol, the goal is to retrieve a given block of the file from a group of servers storing identical copies of it, without telling the servers what block was retrieved. In contrast, our goal is to let servers evaluate a function using an input that is not revealed to them. We show that our constructions are secure, practical and that they can complement existing approaches in storage architectures using multiple cloud providers. The amount of transmitted information during the verification stage of the protocols is proportional to the square root of the length of the file.