Incremental Threshold Scheme Enabled IoT Group Key Management

Cyber landscape evolves rapidly. Internet of Things (IoT) and Edge Computing (EC) have rapidly become an integral part of the modern computing infrastructure. It is expected that there will be more than 50 billion active and connected IoT devices by 2025 [1]. Pervasive IoT/EC creates unprecedented opportunities bridging the gap between previously segregated cyber and physical spaces. However, this progress also brings along new security challenges. IoT devices typically have limited computation, communication, and storage resources. This leads to security architecture designs such as using symmetric keys for group communication. While secure and efficient in stable network settings, symmetric key solutions are ill-adapted for IoT's highly dynamic device mobility behavior and frequent group membership turnover. Whenever IoT members leave a group, the known symmetric keys cannot be made forgotten, posing a serious vulnerability. This leads to frequent re-groupings that require expensive re-authentication, key regeneration, and key redistribution in order to maintain IoT/EC security. We present a novel symmetric key management framework that integrate an Incremental Threshold Scheme (ITS) cryptographical function into communication protocol's key rotation mechanism to allow for secure and efficient symmetric key communication group member node revocation. This ITS-enabled key management framework alleviates the need of frequent and expensive re-grouping and re-keying needed by today's large and dynamic IoT/EC operations. We further applied this ITS-enabled key management framework to a distributed IoT/EC-integrated publish and subscribe framework for applicability validation.

I. Background

Today's pervasive computing often involves a large number of mobile and dynamic IoT/EC devices. There are two essential aspects regarding the operation of such device groups. Firstly, IoT's pervasive connectivity, coupled with omnipresent data collection capability, introduces magnified security and privacy concerns. Secondly, IoT/EC security solutions need to take into consideration resource constraints as these devices (e.g. sensors) typically have only limited computation resources such as CPU, power, storage, and/or communication bandwidth. Resource intensive cryptographical solutions such as full-fledged Public Key Infrastructure (PKI) implementations are typically difficult to apply. This often leads to using symmetric key cryptography to efficiently secure IoT/EC group communication. Under such symmetric key schemes, a trusted managing node (e.g. key distribution center) constructs a communication group by first authenticating all member nodes using relatively expensive asymmetric key management (e.g., PKI based on 2048-bit RSA keys recommended by NIST) based credentials via encrypted tunnels (e.g., IPSEC). Upon successful authentications and authorizations, a sufficiently large symmetric key, e.g., a 256-bit AES key, is distributed to all members/nodes for use as the group communication key. Large symmetric keys are inherently secure in protecting group communication for data sharing. Additionally, a key rotation mechanism is often built-in to periodically and synchronously refresh the symmetric key across all IoT/EC members preventing eavesdropping and key cracking. As such, protocols employing large symmetric keys for group communication are secure and efficient.