Sangjoon Park

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Proxy signatures, introduced by Mambo, Usuda and Okamoto allow a designated person to sign on behalf of an original signer. This paper first presents two new types of digital proxy signatures called partial delegation with warrant and threshold delegation. Proxy signatures for partial delegation with warrant combines the benefit of Mambo's partial(More)
Wireless sensor networks have been used to gather data and information in many diverse application settings. The capacity of such networks remains a fundamental obstacle toward the adaptation of sensor network systems for advanced applications that require higher data rates and throughput. In this paper, we explore potential benefits of integrating(More)
Directional antennas offer many potential advantages for wireless networks such as increased network capacity, extended transmission range and reduced energy consumption. Exploiting these advantages, however, requires new protocols and mechanisms at various communication layers to intelligently control the directional antenna system. With directional(More)
We deal with two claws of Zhou-Gollmann’s fair nonrepudiation protocol. Firstly, their protocol divides a message into 2 parts, i.e., a key K and a ciphertext C. Then, C is delivered to the recipient, while K is submitted to TTP (Trusted Third Party). If the originator doesn’t submit K to TTP , then the protocol appears to have no dispute between the(More)
In this paper, we develop the indoor navigation system based on PDR (Pedestrian Dead Reckoning) using various sensors in smartphone. Usually PDR is consisted of step detection, step length estimation and heading estimation. The issue of PDR is step length estimation and to enhance the accuracy of step length, we apply the walking status recognition(More)
In large scale applications like military surveillance, sensing coverage is essential for target detection and optimization of power consumption is important for lifetime extension of the network. In battle field, nodes are deployed randomly which results some places empty and some places dense. To assure the sensing coverage for the whole area of interest,(More)