## 1 Introduction  
_Ubiquitous computing_ is used to refer to an information environment in which computers are installed everywhere, affecting all areas of a person's life and operating autonomously in a network of linked computers to strongly support the modern human lifestyle. The _ubiquitous networking system_ includes all the technologies needed for infrastructure that enables information to be exchanged anytime and anywhere through a high-speed, large-capacity, broadband network connecting homes, buildings and industrial systems, as shown in Figure 1[1]. As one of the basic infrastructures, sensor networks provide much of the information needed to realize a convenient ubiquitous life. However, the proper security services are indispensable for actualizing the original goals of the ubiquitous networking system. To date, research on security in the ubiquitous networking system has laid disproportionate emphasis on basic security mechanisms, such as authentication or key management. Due to the wireless characteristic or easy physical compromise of sensor nodes, these basic security services are indispensable. However, a defense against possible attacks is also essential to avoid negating much of the promise of ubiquitous networks, because attacks can still be performed even if network communication provides confidentiality and authenticity. As one of the most threatening attacks on the ubiquitous networking system, the jamming attack can intentionally disrupt wireless transmission via interference, noise or collision at the receiver side. To launch the jamming attack, no special hardware is needed; the adversary simply listens to the open medium and broadcasts on the same frequency band as the network. It means that jamming is an effective, low cost attack from the point of view of an attacker, while it is very threatening to wireless users. It can occur either at the physical layer or access layer. Jamming attacks threaten the availability of network resources, and moreover permit real world damage to people's health and safety exceeding simple damages such as loss of sensory data or energy exhaustion of nodes. Figure 1: An example of a ubiquitous networking system. [PERSON] _et al._[2] presented basic defenses against these attacks such as spread-spectrum or authentication, but these straightforward defenses alone are not sufficient for protecting the availabilities of ubiquitous networks. In addition, utilization of the spread spectrum as a defense against jamming on the physical layer can be too energy-consuming to be widely deployed in resource-constrained sensors [3]. Moreover, representative sensor MAC (Media Access Control) protocols, such as S-MAC, B-MAC and T-MAC have considerable vulnerabilities to jamming attacks because of the feature of carrier sensing for transmission [4]. Thus, the simple solution of merely sleeping at the MAC layer after detection cannot be a fundamental solution [5]. Multipath routings on sensor networks [6, 7] could be candidate solutions. However, though they set up multiple disjointed routes with the best hop, they do not provide immediate routes evading the jamming area. As an evasive method for smooth communication after detecting jamming, JAM (Jammed Area Mapping) simply focused on a mapping service of the jamming area [8]. Even though this is a meaningful partial solution, it cannot be a sufficient solution against jamming attacks because it takes time for the routing protocols to update the information, and a route that detours the determined jamming area may induce more jamming on the route if the amount of normal traffic passing the jamming area is huge. Thus, none of the existing defenses support the smooth transmission of normal traffic through immediate evasion of the jamming area. In this paper, we design a routing method, called DMP (Detouring using Multiple Paths), for detouring the jamming (victim) area after detecting jamming and determining the jamming area.