Shingo Okamura

A Consideration of the Precision Improvement in WiFi Positioning System

Recently, WiFi Positioning System (WPS) plays important role in ubiquitous applications. The main problem of WPS is how to collect WiFi Access Point(AP) locations because the most of the APs are usually installed on grass-root basis and their locations are not published.We use Locky.jp provided by Nagoya University Research Group as a WPS for our ubiquitous applications. However the precision of the AP location data in Locky.jp is not enough for our applications. To improve the precision of the AP location database, we are going to apply statistical and heuristic methods. In this paper, we described the overview of our heuristic approach and define the quality of AP observation logs and location data. We also evaluated the quality definition by simple simulations.

Efficient Multi-authorizer Accredited Symmetrically Private Information Retrieval

We consider a setting where records containing sensitive personal information are stored on a remote database managed by a storage provider. Each record in the database is co-owned by a fixed number of parties called data-subjects. The paper proposes a protocol that allows data-subjects to grant access to their records, to self-approved parties, without the DB manager being able to learn if and when their records are accessed. We provide constructions that allow a Receiver party to retrieve a DB record only if he has authorizations from all owners of the target record (respectively, from a subset of the owners of size greater than a threshold.) We also provide a construction where owners of the same record do not have equal ownership rights, and the record in question is retrieved using a set of authorizations consistent with a general access structure. The proposed constructions are efficient and use a pairing-based signature scheme. The presented protocol is proved secure under the Bilinear Diffie-Hellman assumption.

A Metric of Search Efficiency and Preventability of Polluted Contents for Unstructured Overlay

For P2P contents sharing, a construction method of unstructured overlay is known for improving search efficiency and preventability of downloading polluted contents. To design better construction method, we need a good metric of the two performances for overlay. Existent metrics are insufficient for measuring the two performances simultaneously in the situation where there are peers whose probabilities of providing polluted contents are diverse. In this paper, a metric of the two performances for overlay is proposed. By simulations, we confirm that proposed metric is effective in contents sharing on overlay where there are peers whose probabilities of providing polluted contents are diverse.

An Authentication System Development in Application of Grid Middleware to a Nationwide Joint-Use Environment for Computing

In the Cybermedia Center, Osaka University (CMC), we have applied the NAREGI grid middleware to our latest large-scale computing system for nationwide joint-use, and have made grid computing technology available on them coexisting with the conventional computing style. In this paper, we will describe an authentication system solving the problems which we have encountered in construction of the grid environment.

An Anonymous Authentication Protocol for Smart Grid

Smart Grid allows users to deal with information related to the electricity usage via IP networks, and then guarantee of both validity and privacy of information is necessary for users. In our future scope, the electricity bill used by consumers may be charged to the consumers themselves via the Smart Grid, even outside their homes. Such information is strictly related to privacy of consumers and hence we propose an anonymous authentication protocol for the electricity usage on the Smart Grid. Our main idea is to utilize group signatures with controllable linkability. In these group signatures, only designated signers can generate digital signatures with anonymity under a single group public key, and only entities with a link key can distinguish whether the signatures are generated by a same signer or not. Whereas our proposed protocol is able to include any group signature scheme with controllable linkability, we also propose new controllably linkable group signatures with tokens, which are handled by smart meters on the Smart Grid.

SPaCIS: Secure Payment Protocol for Charging Information over Smart Grid

A use of an electric outlet by a consumer forces the outlet manager to pay for the consumer’s power usage in current electrical power systems. Even if a consumer uses an outlet managed by another person, one bill for both indoor and outdoor charging information should be required to the consumer in their contract with the utility company. For this purpose, we define a model for the Smart Grid security and propose a Secure Payment Protocol for Charging Information over Smart grid, SPaCIS for short, as a protocol satisfying the model. Our model provides for the unlinkability of consumers as well as for the undeniability and unforgeability of billing information using digital signatures and identity federations. SPaCIS is also efficient in the sense that time complexity is constant relatively to a trivial use such as an individual verification for each signatures, unless a verification error happens. We furthermore evaluate performance of SPaCIS via cryptographic implementation, and simulate SPaCIS in a case that one thousand users generate thirty signatures. Then, we show that SPaCIS with ECDSA can be executed within 6.30 msec for signing and 21.04 msec for verification of signatures, and conclude that SPaCIS is fairly practical.

An Approach for Filtering Inaccurate Access Point Observation Report in WiFi Positioning System

WiFi Positioning System (WPS) plays important role in Ubiquitous applications. It shows shorter response time than GPS and provides more precise position than Cell towers. It is widely used in hybrid positioning systems, e.g. GPS and WPS. The main problem of WPS is how to collect WiFi Access Point (AP) positions because the most of AP positions are not published. So thus, WPS providers collect AP positions by themselves or rely on the WPS users report. There are several WPS provided, some are commercial system and the others are voluntarily provided. Outdoor position estimation method are already established in commercial system, however, the indoor case requires some more researches. It is necessary to keep voluntarily WPSs. In this paper, we propose an open method to select precise position reported by users to keep WPS estimation accuracy. The proposed method is basically based on the precision preservation methods used in GPS. WPS does not have the same degree of accuracy as GPS, it should be verified the effectiveness in WPS. We have some consideration about the applicability of the proposed method.

A Report of Campus-Wide IT Authentication Platform System Development in Osaka University

Cybermedia Center, Osaka University (CMC) is now developing campus-wide IT authentication platform system (CITAPS). In this paper, we report the current status of CITAPS development. Before installing CITAPS, unified account system (UAS) served as an authentication platform system. First of all, we describe the issues in UAS, and then we show how to solve these issues in CITAPS and the future works

ISDSR: Secure DSR with ID-based Sequential Aggregate Signature

Wireless sensor networks are often more vulnerable than wired ones. Especially, an adversary can attack the networks by utilizing false route information. A countermeasure against the attack is a secure routing protocol with digital signatures to guarantee the validity of route information. However, existing secure routing protocols are inefficient because the memory size and the computational overhead are heavy. To overcome these problems, we focus on ID-based sequential aggregate signatures (IBSAS) (Boldyreva et al., 2007). IBSAS allow users to aggregate individual signatures into a single signature. Moreover, certificates of public keys are unnecessary for IBSAS. Therefore, IBSAS can drastically decrease the memory size and the computational overhead. Besides, one of the main concerns for practical use is to construct a protocol specification with IBSAS. Moreover, since IBSAS are sometimes weak against compromising secret keys, another concern is to construct its countermeasure. For these purposes, we propose a secure dynamic source routing with ID-based sequential aggregate signatures, called ISDSR for short and discuss the key management to revoke/update compromised keys. We also show that the performance of ISDSR is the best in comparison with the existing protocols.

A Private and Consistent Data Retrieval Scheme with Log-Squared Communication

Data retrieval is used to obtain a particular data item from a database. A user requests an item in the database from a database server by sending a query, and obtains the item from an answer to the query. Security requirements of data retrieval include protecting the privacy of the user, the secrecy of the database, and the consistency of answers. In this paper, a data retrieval scheme which satisfies all the security requirements is defined and an efficient construction is proposed. In the proposed construction, the size of a query and an answer is O((log N)2), and the size of data published by the database server when the database is updated is only O(1). The proposed construction uses the Merkle tree, a commitment scheme, and Oblivious Transfer. The proof of the security is given under the assumption that the used cryptographic schemes are secure.