We present "WARASHIBE," a fair data-data exchange protocol between two parties on the blockchain. Several data-cryptocurrency exchange protocols on the blockchain have been proposed, but there are significant technical challenges for direct data-data exchanges. To bridge this gap, we propose "WARASHIBE" , a fair data-data exchange protocol, which extends existing fair data-cryptocurrency exchange protocols under a novel yet practical assumption: honest parties do not incur financial losses even if malicious behavior occurs. We formalize the protocol within the Universal Composability (UC) framework. By implementing and evaluating the protocol on the Ethereum blockchain, we demonstrate that WARASHIBE is feasible for fair data-data exchange.

To receive effective treatment during emergency response due to seizures or unforeseen accidents, a patient with intractable diseases must disclose information about their disease to an emergency physician. If the patient loses consciousness while traveling, the patient should disclose this information to a companion in advance. However, disclosing this information to a companion is undesirable because the information is confidential. Thus, we propose a system that discloses specific information on intractable diseases only when an emergency physician has verified they possess a medical license. Otherwise, the proposed system only discloses appropriate first aid information. We implemented a prototype of the proposed under the assumption that a physician has a digital medical license based on verifiable credentials (i.e., a standard for digital credentials). With this system, the patient does not disclose confidential information to the patient’s companion but does disclose necessary information to the emergency physician.

Improvements in fabrication devices such as 3D printers are becoming possible for personal fabrication to freely fabricate any products. To clarify who is liable for the product, the fabricator should keep the fabrication history in an immutable and sustainably accessible manner. In this paper, we propose a new scheme, "Fabchain," that can record the fabrication history in such a manner. By utilizing a scheme that employs a blockchain as an auditable communication channel, Fabchain manages print jobs for the fabricator’s 3D printer over the blockchain, while maintaining a history of a print job. We implemented Fabchain on Ethereum and evaluated the performance for recording a print job. Our results demonstrate that Fabchain can complete communication of a print job sequence in less than 1 minute on the Ethereum test network. We conclude that Fabchain can manage a print job in a reasonable duration for 3D printing, while satisfying the requirements for immutability and sustainability.

There are several studies that propose identity management that utilizes blockchain technology. In Ethereum, the main programmable blockchain system, data on a blockchain are saved as encoded binaries for executing automatic verification. To decode a binary, users need to know the application binary interfaces (ABI) that describes the data structure of the registered information. However, the manner by which ABI are shared in the current blockchain protocol is opaque. To resolve this problem, we describe a new protocol for embedding the ABI on a blockchain transaction when a registrant registers information. Our method enables users to read registered data with information on the blockchain alone, and it guarantees transparency without requiring users to trust third parties.

Frequent and uncontrolled interruptions by information systems that do not reflect the user’s state can result in fragmented working times and decreased intellectual productivity. To avoid adverse interruptions, interruptibility estimation methods based on PC operation information have been proposed. However, workers who use PCs to accomplish their primary tasks occasionally engage in paperwork. Occasional paperwork activities, which are not reflected in the PC’s operation information, can cause estimation errors. This study focuses on using the position of the head, posture, temporal motion, and continuity of the head position and posture while a worker is at his or her desk as indices to reflect engagement in the task at hand. Based on an analysis of the relationship between the head-related parameters and interruptibility, an interruptibility estimation algorithm is proposed using four head-related indices that reflect interruptibility during PC and non-PC work. Experiments indicate that estimation accuracy improves as a result of incorporating these indices in the algorithm.