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Wireless sensor networks (WSNs) consist of sensors, gateways and users. Sensors are widely distributed to monitor various conditions, such as temperature, sound, speed and pressure but they have limited computational ability and energy. To reduce the resource use of sensors and enhance the security of WSNs, various user authentication protocols have been(More)
An anonymous user authentication scheme allows a user, who wants to access a remote application server, to achieve mutual authentication and session key establishment with the server in an anonymous manner. To enhance the security of such authentication schemes, recent researches combined user's biometrics with a password. However, these authentication(More)
In multi-server environments, user authentication is a very important issue because it provides the authorization that enables users to access their data and services; furthermore, remote user authentication schemes for multi-server environments have solved the problem that has arisen from user's management of different identities and passwords. For this(More)
In wireless sensor networks (WSNs), a registered user can login to the network and use a user authentication protocol to access data collected from the sensor nodes. Since WSNs are typically deployed in unattended environments and sensor nodes have limited resources, many researchers have made considerable efforts to design a secure and efficient user(More)
Remote User authentication scheme is widely used for communication between authorized remote users over insecure network. In 2010, Manoj Kumar proposed a new secure remote user authentication scheme with smart cards. He claimed that the protocol was secure against replay attack, stolen verifier attack. However, we show that the protocol is vulnerable to(More)
Remote user authentication schemes are commonly used for communication between authorized users and remote servers over an insecure network. Due to its simplicity and convenience this method is widely used in many environments, such as sensor networks or remote host login systems. In recent years, several remote user authentication schemes using smart cards(More)
A city is a dynamic entity, which environment is continuously changing over time. Accordingly, its virtual city models also need to be regularly updated to support accurate model-based decisions for various applications, including urban planning, emergency response and autonomous navigation. A concept of continuous city modeling is to progressively(More)