Joo Seok Song

Knowledge-proof based versatile smart card verification protocol

We propose a zero-knowledge interactive proof based identification and signature scheme. The protocol is based on Eulers totient function and discrete logarithms over the ring Z/nZ, and can be applied to smart cards. A prover keeps a signed subgroup generator provided by a trusted center as its secret information. Our scheme has symmetricity in the sense that the same computational complexity and the same hardware both for Prover and for Verifier are required. Also, it requires minimal amount of computation and communications for secret information. The protocol is versatile enough to be applicable to digital signature scheme, multiple digital signature scheme and key exchange protocol. We outline those protocols to show the versatility of our protocol.

Methods to use 6LoWPAN in IPv4 network

6LoWPAN is low power wireless personal area network based on IPv6 and IEEE802.15.4. It is used for transmission of IPv6 packets. But there are no ways for IPv4 hosts to connect 6LoWPAN, current Internet users cant use 6LoWPAN until IPv6 is deployed. In this paper, we propose the methods to use 6LoWPAN in IPv4 network so that IPv4 user can also utilize 6LoWPAN techniques.

AOZDV: An Enhanced AODV Protocol based on Zone Routing in MANET

In MANET, AODV is one of famous on-demand routing protocols, which uses the routing tables in the nodes if possible, or a RDP (route discovery process) is triggered to find a new route. However, in the large MANET, the network performance becomes worse because of the limitations of RDP. In this paper, we propose a novel routing protocol, named AOZDV (ad hoc on-demand zone and distance-vector routing), which enhances the AODV protocol through zone routing. AOZDV creates a zone with neighbor nodes of the source/destination using traffic and power information, and it utilizes a destination-vector table for internal-zone routing while it adopts the AODV protocol for outer-zone routing. Using simulations, we prove that AOZDV can reduce the rate of route loss rate and RDP caused by route loss compared with DSR and AODV.

Preventing Double-Spent Coins from Revealing User's Whole Secret

Most digital cash systems have the identity revelation capability under the condition of double-spending, but the capability may be misused as a framing tool by Bank. We present a method that provides both the identity revelation capability and the framing prevention property.

A Vertical Handoff Algorithm Using MN Velocity for WiBro and WLAN

Integration of communication networks has been accelerated and is recognized as an important evolution plan of the existing networks such as WiBro (wireless broadband Internet) and WLAN (wireless LAN). There are two ways to integrate these networks: loose coupling and tight coupling. The loose coupling approach provides separate data paths, while the tight coupling provides a full integration of different networks. The loose coupling is worse in seamless mobility, QoS (quality of service) provision, and network security. In order to lessen the problems of loose coupling and improve tight coupling method, we propose a new convergence network architecture that allows users to roam between cells in wireless overlay networks. Also, we propose a vertical handoff algorithm for WiBro and WLAN networks. Our algorithm reduces handoff oscillation (so-called ping-pong effect) in which a MN (mobile node) with speed moves back and forth in two networks in a short time. We consider the speed of MN and the distance between MN and AP (access point). When MN moves on the overlapped area of two networks, we calculate DT (dwell time) value to reduce unnecessary handoff. The simulation results show that the total throughput can be increased by using proper DTthreshold value.

An overload control of SCP in advanced intelligent network with fairness and priority

In this article we propose two mechanisms for overload control SCP in AIN; continuous gapping method and new arrival gapping method. They are all interactive mechanisms in which as SCP and SSPs exchange load information for overload control. These mechanisms are based on the general ACG, however different call gapping times are applied to each SSP under the fairness scheme. Also in the mechanisms, priority scheme is implemented. The analytic and simulation results show that the call throughput in the two mechanisms is almost same and fairness about the probability of rejection is maintained with the same value on all SSPs. On the priority scheme, new arrival gapping method has better priority achievement than continuous gapping method.

Cluster based emergency message dissemination scheme for vehicular ad hoc networks

Wireless and mobile communications has experienced an unprecedented rapid growth during the last decade. Vehicular Ad Hoc Networks (VANETs) are a completely wirelessly connected through the nodes, which usually has dynamic topologies. VANETs can be employed in many applications such as traffic control, safety related message dissemination, and entertainment infotainment. Broadcast storm problem is one of the hot issues in VANETs as it lacks of central management. Many methods are proposed to solve this problem, such as p-persistence based, 1-persistance based, and counter based schemes. However, all of the related works have weaknesses that cannot be ignored either associated with intersection problem or limited environment. In this paper, a novel clustering algorithm is proposed that guarantees efficient clustering. Thereafter, an efficient cluster maintenance mechanism is proposed. Then we show how the emergency messages are transmitted in proposed cluster structure. Finally, the simulation study confirms the availability and efficiency of the proposed clustering algorithm.

Throughput-Based MAC Layer Handoff in WLAN

We propose a MAC layer handoff mechanism for IEEE 802.11 WLAN to give benefit to bandwidth-greedy applications at STAs. In order to find an optimal AP, we investigate a new measurement method called TFC (Transient Frame Capture) to estimate the achievable throughput from APs. Since TFC is employed under promiscuous mode, it avoids service degradation through the current associated AP. In addition, the mechanism is a client-only solution which does not require any modification on APs. We develop an analytic model for the throughput estimation and demonstrate it through experimental studies.

A routing protocol for throughput enhancement and energy saving in mobile ad hoc networks

Mobile nodes communicate with each others having the limited energy in mobile ad hoc networks. The large amount of control packets and the frequent flooding of control packets cause energy exhaustion of nodes. The main goal of routing protocols in mobile ad hoc networks is throughput enhancement. Hence, this paper proposes a new routing protocol for mobile ad hoc networks called the Routing Protocol for Throughput Enhancement and Energy Saving (TEES) in mobile ad hoc networks. The simulation results show that TEES increases the amount of packet delivery and reduces the control packet overhead.

An optimized test sequence satisfying the completeness criteria

We present a problem of commonly used characterization sequences and propose a new test sequence to resolve the problem. The proposed test sequence could decide whether the output fault arises in the edge being tested or one of edges in the UIO sequence. Additionally, the fault coverage is much wider than other test sequence generation methods. To achieve the goal, we introduce k-strong FSM, and show that it can be constructed from a characterization sequence. Also, we show that the length of the test sequence satisfying the completeness can be reduced. Finally, we illustrate our technique on a specific example.