# Securing IoT: Mitigating Sybil Flood Attacks with Bloom Filters and Hash Chains
## 3 Related Work
This helps to prevent unauthorized access to the smart home system. The protocol utilizes a hash chain to fragment and verify the integrity of firmware updates for IoT devices. This ensures that the firmware remains unaltered during distribution. Additionally, the protocol utilizes the hash chain to dynamically update secret key values between communicating devices. This helps to prevent unauthorized access by ensuring that the shared secret is regularly refreshed. While the cumulative hash chain shares some similarities with blockchain technology in terms of chaining hash values together, it is not considered a blockchain due to differences in the structure, decentralization, and consensus mechanism. The protocol instead focuses on chaining hash values together to create a tamper-evident record. This approach ensures data authenticity and prevents unauthorized modifications. Additionally, the secret key is updated in every session, further enhancing the security of the communication channel. By verifying the identities of communicating devices, ensuring the integrity of data transmissions, and preventing unauthorized access attempts through dynamic key updates, integration of the cumulative keyed-hash chain strengthens the security of the proposed protocol. The proposed solution, while effective, may not be suitable for deployment in current smart home environments due to the inherent resource limitations of many smart home devices, which often preclude the use of asymmetric cryptographic techniques. In [23], the authors addressed the critical security challenge of replay attacks within IoT authentication schemes. Traditional defense mechanisms, which rely on timestamps or extensive nonce storage, are often impractical due to the resource constraints of IoT devices. Additionally, reliance on shared secrets such as session keys necessitates robust key management practices. These keys could be compromised if not securely stored or transmitted, undermining the entire authentication process. Thus, they introduced a novel lightweight user authentication scheme employing an improved challenge-response mechanism. The approach was designed to resist replay attacks without requiring time synchronization or large nonce lists, making it suitable for resource-limited IoT environments. By utilizing randomly generated nonces during authentication, the scheme ensures message freshness and mutual authentication between users and sensors, effectively mitigating the risk of replay attacks. A performance evaluation demonstrated that the scheme significantly outperformed existing methods in terms of storage and computational costs, making it efficient for IoT devices. Although communication overhead is reduced in certain interactions, it may increase slightly due to the absence of timestamps. However, the scheme's dependence on key management remains a critical consideration; any compromise in key storage or transmission could jeopardize the security of the entire system. Overall, the above paper presents a secure and efficient authentication solution tailored to the unique challenges of the IoT environment while highlighting the essential need for robust key management to ensure the integrity of the authentication process. While the primary focus of the current paper is on sybil flood defence, we acknowledge the importance of addressing other potential vulnerabilities such as replay attacks. To mitigate this risk, we have incorporated a timestamp mechanism into our proposed solution. While a deeper discussion of replay attacks and their mitigation strategies is beyond the scope of this work, the included timestamp mechanism provides a practical and effective countermeasure. For additional context, readers may refer to the existing literature on replay attacks in IoT environments, such as [24; 25].