Digital signatures serves as a crucial cryptographic primitive in an e-governance system for the authentication of citizen-government interactions. Traditional methods (DSA, ECDSA) pose computational overheads at resource-limited endpoints and centralized verification servers. While complex-number cryptography provides theoretical efficiency through the Complex Discrete Logarithm Problem (CDLP), prior works often fail to meet the requirements for real-world applications. This paper advances the knowledge in lightweight cryptography by introducing LDSEGoV, a lightweight digital signature scheme for e-governance infrastructure. The proposed method overcomes the shortcomings of previous methods by incorporating sound modular arithmetic for consistent verification, using NIST-approved hash functions. Furthermore, we provide a comprehensive security analysis that provides the formal security proofs of existential unforgeability (EUF-CMA) of the proposed scheme in the Random Oracle Model. Additionally, the experimental results show a 6.5× improvement in signing performance and a 24.76× improvement in verification performance over ECDSA, with a 61% reduction in signature size. These results demonstrate that LDSEGoV is suitable for large-scale digital governance systems for authentication scenarios.