DaeHun Nyang

Group signatures with controllable linkability for dynamic membership

In this paper we present a novel group signature scheme for dynamic membership which enables fine-grained control over the release of user information. This scheme could be widely used for various anonymity-based applications such as privacy-preserving data mining and customized anonymous authentication owing to a useful property called controllable linkability. A valid signer is able to create signatures that hide his or her identity as normal group signatures but can be anonymously linked regardless of changes to the membership status of the signer and without exposure of the history of the joining and revocation. From signatures, only linkage information can be disclosed, with a special linking key. Using this controllable linkability and the controllable anonymity of a group signature, anonymity may be flexibly or elaborately controlled according to a desired level. To begin construction of our scheme, we first introduce the Decision Linear Combination (DLC) assumption in a so-called gap Diffie-Hellman group where the DDH problem is tractable but the CDH problem is hard, and we prove that this assumption can be guaranteed in generic bilinear groups. To identify security requirements more precisely, we formally present definitions of anonymity, traceability, non-frameabilty, and linkability. We then prove that our scheme achieves all these security properties in the random oracle model. Our scheme supporting controllable linkability yields a short signature that is only 33.3% longer than the best-known normal group signature. Furthermore, we show that our scheme is comparable to the group signature scheme in terms of the amount of computation for basic operations such as signing, verification, and the key update caused by revocation. Finally, using the linkability for dynamic membership, computation overhead in opening signers identity can be significantly reduced or minimized.

Software-Based Remote Code Attestation in Wireless Sensor Network

Sensor nodes are usually vulnerable to be compromised due to their unattended deployment. The low cost requirement of the sensor node precludes using an expensive tamper resistant hardware for sensor physical protection. Thus, the adversary can reprogram the compromised sensors and deviates sensor network functionality. In this paper, we propose two simple software-based remote code attestation schemes for different WSN criterion. Our schemes use different independent memory noise filling techniques called pre-deployment and post-deployment noise filling, and also different communication protocols for attestation purpose. The protocols are well-suited for wireless sensor networks, where external factors, such as channel collision, result in network delay. Hence, the success of our schemes of attestation does not depend on the accurate measurement of the execution time, which is the main drawback of previously proposed wireless sensor network attestation schemes.

RFID authentication protocol with strong resistance against traceability and denial of service attacks

Even if there are many authentication protocols for RFID system, only a few protocols support location privacy. Because of tag’s hardware limitation, these protocols suffer from many security threats, especially from the DoS (Denial of Service) attacks. In this paper, we discuss location privacy problem and show vulnerabilities of RFID authentication protocols. And then, we will suggest a strong authentication protocol against location tracing, spoofing attack, and DoS attack.

Proactive code verification protocol in wireless sensor network

For WSN(Wireless Sensor Network) to provide reliable service, authentication is one of the most important requirements. The authentication usually means the entity authentication, but owing to the data centric nature of sensor network, much more importance must be put on the authentication(or attestation) for code of sensor nodes. The naive approach to the attestation is for the verifier to compare the previously known memory contents of the target node with the actual memory contents in the target node, but it has a significant drawback. In this paper, we show what the drawback is and propose a countermeasure. The basic idea of our countermeasure is not to give the malicious code any memory space to reside by cleaning the target nodes memory space where the malicious code can reside. This scheme can verify the whole memory space of the target node and provides extremely low probability of malicious codes concealment without depending on accurate timing information unlike SWATT[1]. We provide this verification method and show the performance estimation in various environments.

Short Dynamic Group Signature Scheme Supporting Controllable Linkability

The controllable linkability of group signatures introduced by Hwang et al. enables an entity who has a linking key to find whether or not two group signatures were generated by the same signer, while preserving the anonymity. This functionality is very useful in many applications that require the linkability but still need the anonymity, such as sybil attack detection in a vehicular ad hoc network and privacy-preserving data mining. In this paper, we present a new group signature scheme supporting the controllable linkability. The major advantage of this scheme is that the signature length is very short, even shorter than this in the best-known group signature scheme without supporting the linkability. We have implemented our scheme in both a Linux machine with an Intel Core2 Quad and an iPhone4. We compare the results with a number of existing group signature schemes. We also prove security features of our scheme, such as anonymity, traceability, nonframeability, and linkability, under a random oracle model.

Cooperative public key authentication protocol in wireless sensor network

Recent measurements for Public Key Cryptography (PKC) protocols on 8-bit wireless sensor nodes showed optimistic results. It has been shown that Elliptic Curve Cryptography (ECC) is quite applicable to WSN. Still, PKC is much expensive in terms of computation and memory compared by the Symmetric Key Cryptography (SKC). In addition, in PKC, each public key needs to be authenticated before it’s used. We believe that sooner or later, PKC will be widely deployed in WSN. Therefore, we present a cooperative distributed public key authentication scheme that does not require any cryptographic overhead. In our scheme, each node is let to store a few number of hashed keys for other nodes. When a public key authentication is required, nodes who store this key help in authenticating it in a distributed and cooperative way. We consider the constrained resources of the sensor node. Additionally, we extend our scheme to fit with small range of authentication error.

Privacy in Location Based Services: Primitives Toward the Solution

Location based services (LBS) are one of the most promising and innovative directions of convergence technologies resulting of emergence of several fields including database systems, mobile communication, Internet technology, and positioning systems. Although being initiated as early as middle of 1990s, it is only recently that the LBS received a systematic profound research interest due to its commercial and technological impact. As the LBS is related to the users location which can be used to trace the users activities, a strong privacy concern has been raised. To preserve the users location, several intelligent works have been introduced though many challenges are still awaiting solutions. This paper introduces a survey on LBS systems considering both localization technologies, model and architectures guaranteeing privacy. We also overview cryptographic primitive to possibly use in preserving LBSs privacy followed by fruitful research directions basically concerned with the privacy issue.

Fuzzy face vault: how to implement fuzzy vault with weighted features

Ari Juel et al from ISIT 2002 presented a fuzzy vault scheme, which is a framework to encrypt a cryptographic key with a fuzzy key[5]. Following their framework, many trials to implement mainly a fuzzy finger vault have been proposed that enables us to keep secretly a key with our finger print. Our work is to focus on instantiating the fuzzy information of the fuzzy vault scheme with human faces instead of fingers. Most of face authentication algorithms are dependent upon weighted features, which are incompatible with the original fuzzy vault scheme. To reflect the level of importance of individual features from feature set, we introduce another layer between captured feature set and points in the polynomial to be interpolated.

Grid-Based Key Pre-Distribution in Wireless Sensor Networks

In this paper, we introduce a grid-based key pre-distribution scheme in wireless sensor networks, which aims to improve the connectivity and resiliency while maintaining a reasonable overhead. We consider simplification of the key establishment logic and enhancement of the connectivity via plat polynomial assignment on a three-dimensional grid for node allocation and keying material assignment. We demonstrate that our scheme results in improvements via a detailed discussion on the connectivity, resource usage, security features and resiliency. A comparison with other relevant works from the literature along with a demonstrated implementation on typical sensor nodes shows the feasibility of the introduced scheme and its applicability for large networks.

On grid-based key pre-distribution: toward a better connectivity in wireless sensor network

In this paper, we revisit Grid-Based Key Pre-Distribution Scheme in Wireless Sensor Network to investigate improving the connectivity of the network and maintain both the security level and communication overhead. Both of the original work and our modification are based on using symmetric bivariate polynomials for generating cryptographic keys. In addition, their work relies on the usage of multi-dimensional grid to assign the polynomials on the sensor nodes allocated on the intersections of the grid and provide a needed connectivity. In this work we consider the simplification of the key establishment logic, the enhancement of connectivity in what we call the plat polynomial assignment. We present detailed discussion on the connectivity, resources usage, and security features that shows better results on the side of the connectivity, intermediate node discovery and security measurement. Finally, we provide a comparison between our results and other existing solutions including the revisited scheme.