Retraction Note to: Novel Sybil attack detection using RSSI and neighbour information to ensure secure communication in WSN

Wireless sensor networks (WSN) are generally employed in unattended hostile areas such as forest monitoring, agriculture fields, military battlefields. An adversary can physically capture WSN deployed in a hostile environment. Once an adversary captures a node, the cryptographic information and the software program can be easily extracted. Also, the adversary can reprogram the software inside the node. After reprogramming, the adversary can replicate and deploy the node with multiple identities to do malicious activities. This kind of identity theft attack can be classified as Clone attack or Sybil attack. These identity theft attacks are addressed by many distributed, centralised and localised solutions. Most of these solutions utilise private/public key, and symmetric key algorithms are energy and memory demanding, while the WSN are energy and memory constrained. This paper proposes a novel Sybil attack detection protocol (NoSad) to identify and isolate the Sybil attack in WSN. This protocol is a localised method using intra-cluster communication and RSSI value to identify the Sybil node. The proposed protocol is simulated extensively with various topologies, and obtained results prove that the protocol is highly efficient in detection ratio, energy utilisation, memory usage, computation and communication requirement. This protocol may be used in any resource-constrained WSN to obtain a satisfactory result. This work provides a solution for different scenarios of Sybil node position to counter the Sybil attack in WSN.