Editorial Secure multi-mode systems and their applications for pervasive computing Pervasive computing environments present specific peculiari- ties with respect to aspects like security and multimodality. As a matter of fact, the accessibility level of a virtual environment can definitively be improved by natural interfaces and multimodal interaction systems, which offer users the freedom to select from multiple modes of interaction with services and permit to break down barriers about human–computer interaction making com- munication intuitive and spontaneous. On the other hand, while enlarging and easing the ways to access to the environment, secu- rity threads arise and the environment must be properly equipped in order to protect itself from malicious attacks and/or from wrong actions performed by inexpert users. This special issue brings together 17 contributions, with both theoretical and practical results of significance on aspects of mul- timodality and security in pervasive applications and environ- ments. The contributions vary from themes like multimodal interactions to privacy and access control schemes for pervasive environments. The paper ‘‘Handling uncertainty in multimodal pervasive com- puting applications” by Marie-Luce Bourguet and Marie-Luce Bourguet, deals with recognition-based interaction techniques used in multimodal interfaces (e.g. speech and gesture recognition) and presents an experimental study into users’ synchronisation of speech and pen inputs in error correction. The paper ‘‘Middleware mechanisms for supporting multimodal interactions in smart environments” authored by Antonio Coronato and Giuseppe De Pietro focuses on multimodal interactions in per- vasive environments and presents a middleware infrastructure to support such interactions. The paper ‘‘A study on secure RFID mutual authentication scheme in pervasive computing environment” authored by Soo-Young Kang, Im-Yeong Lee and Deok Gyu Lee after having introduced several authentication schemes proposes a new one for secure mutual authentication in RFID-based systems. The paper ‘‘Further improvement on a novel privacy preserving authentication and access control scheme for pervasive computing environments” authored by Chun-Ta Li, Min-Shiang Hwang, and Yen-Ping Chu describes improvements on a scheme for preserving privacy and controlling access in a pervasive environment. The paper ‘‘An efficient end-to-end security mechanism for IP multimedia subsystem” authored by Chi-Yuan Chen, Tin-Yu Wu, Yueh-Min Huang, and Han-Chieh Chao proposes a key exchange protocol that is also able to mitigate the impact of the spam over IP telephony. The paper ‘‘A unified security framework with three key man- agement schemes for wireless sensor networks” authored by Rabia Riaz, Ayesha Naureen, Attiya Akram, Ali Hammad Akbar, Ki-Hyung Kim, and H. Farooq Ahmed presents a unified security framework with three key management schemes, SACK, SACK-P, and SACK-H that incorporate symmetric key cryptography, asymmetric key cryptography and the hybrid. The paper ‘‘A trust-based secure service discovery (TSSD) model for pervasive computing” authored by Sheikh I. Ahamed and Mous- humi Sharmin presents a trust based secure Service discovery model, TSSD (Trust-based Secure Service Discovery) for a truly pervasive environment that allows both secure and non-secure discovery of services. The paper ‘‘Security co-existence of wireless sensor networks and RFID for pervasive computing” authored by Bo Sun, Yang Xiao, Chung Chih Li, Hsiao-Hwa Chen, and T. Andrew Yang presents their security concerns and related solutions and proposes a Linear Con- gruential Generator based lightweight block cipher that can meet security co-existence requirements of WSNs and RFID systems for pervasive computing. The paper ‘‘Location management scheme with WLAN positioning algorithm for integrated wireless networks” authored by Chih-Hsiung Tseng and Sheng-Tzong Cheng presents a location management scheme for integrated wireless networks and a signal-based position- ing algorithm for WLAN. The paper ‘‘Self-optimization of secure web services” authored by Valentina Casola, Umberto Villano, Massimiliano Rak, Emilio Mancini and Nicola Mazzocca deals with an autonomic framework that makes it possible to auto-configure and to auto-tune the com- position of services, guaranteeing optimal performance and the fulfillment of given security requirements. The paper ‘‘Group-based intrusion detection system in wireless sensor networks” authored by Guorui Li, Jingsha He and Yingfang Fu presents an intrusion detection algorithm that takes into ac- count multiple attributes of the sensor nodes in a wireless sensor network. The paper ‘‘A secure network management protocol for Smart- Grid BPL networks: design, implementation and experimental results” authored by Markos P. Anastasopoulos, Artemis C. Voulkidis, Athanasios V. Vasilakos and Panayotis G. Cottis proposes a secure device management protocol targeted to large scale Broadband over Power Line (BPL) networks. The paper ‘‘A trust-based security system for ubiquitous and per- vasive computing environments” authored by Azzedine Boukerche and Yonglin Ren proposes a security system based on trust manage- ment that involves developing a trust model, assigning credentials to nodes, updating private keys, managing the trust value of each node, and making appropriate decisions about nodes’ access rights. The paper ‘‘A packet marking with fair probability distribution function for minimizing the convergence time in wireless sensor network” authored by Bo-Chao Cheng, Huan Chen, Yi-Jean Li and Ryh-Yuh Tseng proposes an equality approach to deal with the 0140-3664/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.comcom.2008.09.028 Computer Communications 31 (2008) 4232–4233 Contents lists available at ScienceDirect Computer Communications journal homepage: www.elsevier.com/locate/comcom