Secure Consensus in Distributed Systems: Raft Protocol with Hybrid Cryptography

Consensus protocols for computer networks, such as Raft and Paxos, are typically deployed in cloud computing environments and assume that participating nodes possess fixed, known identities for performing log replication. This identity assumption presents a significant attack vector, particularly for Sybil attacks, because the protocol lacks authentication mechanisms to verify the identities of nodes joining the consensus process, a vulnerability stemming from the crash-fault-tolerant design that presumes nodes either function correctly or fail completely, without accounting for malicious or compromised (Byzantine) behaviour. In this study, we present CryptObj, a secure adaptation of the Raft protocol that employs hybrid cryptography, combining Rivest–Shamir-Adleman (RSA) and Elliptic Curve Cryptography (ECC) with symmetric ciphers such as Advanced Encryption Standard (AES) and ChaCha20, using Public Key Infrastructure (PKI) key wrapping and Transport Layer Security (TLS) as alternative cryptographic schemes. The system provides node authentication via a Certificate Authority (CA), alongside confidentiality for the RequestVote phase. This phase is formally verified using an AnBx model. This adaptation enables the deployment of security-critical applications that require a secure consensus primitive, such as access control models. Our experimental evaluation, conducted across cluster sizes up to nine nodes, demonstrates that CryptObj exhibits low overhead for RSA 2048 and ECC configurations, while RSA 4096 incurs significantly higher decryption and signing latency.