A Robust Security Scheme Based on Enhanced Symmetric Algorithm for MQTT in the Internet of Things.

Message Queuing Telemetry Transport (MQTT) is expected to be the de facto messaging IoT standard. Therefore, MQTT must achieve efficient security. Nevertheless, the most significant drawback of the MQTT is its lack of protection mechanisms. Meanwhile, the existing approaches have added processing overhead to the devices and are still vulnerable to various attacks. Therefore, this research work presented an integrated scheme known as the Robust Security Scheme (RSS) to protect the MQTT against any exploitations that might result in sophisticated cyberattacks. The proposed RSS employs two cryptosystems: 1) a dynamic variant of the Advanced Encryption Standard (D-AES); and 2) Key-Policy Attribute-Based Encryption (KP-ABE). RSS introduces a new design architecture of the symmetric AES algorithm to encrypt the MQTT payload called D-AES. Additionally, the second part of the proposed hybrid cryptosystem is KP-ABE, which is utilized to cipher the private key of the proposed D-AES to avoid the computation overhead of bilinear maps. The performance of the proposed RSS is measured in terms of processing time and traffic overhead. Additionally, the security aspects are evaluated in terms of balance, avalanche effect, and hamming distance and compared to the existing works in a testbed environment. Results revealed that the proposed D-AES is more promising with improvements than the standard AES algorithm. The proposed scheme achieves polymorphism while maintaining interoperability. RSS exhibited improvements over the standard AES algorithm by 8.75%, 10.45%, and 6.81% in terms of balance, avalanche effect, and hamming distance, respectively.