## 10 Discussion
A national identity card is the first thing enumerators ask during the conduction of a national housing and population census. The Census Bureau is responsible for covering data collection in the houses of identity card holders; the major limitation of the Bureau, therefore, was its ignorance of homeless/minority/discriminated communities, refugees, and non-identity card holders (referred to as missing persons in the census count). We proposed thumbprint collection in the census process--only mandatory for non-ID card holders, so that they could be verified by the NADRA. In contrast, if their records did not exist, these people would provide a corner case for policymakers to analyze such cases and propose some form of identity to have them listed in the official database. In the future, the verification of thumbprint could be possible on the go, and the usage and cost of the IPFS would be minimized as well. In terms of managing user identity, an encryption method has been applied in our model to protect identity data (national ID card and thumbprint) both at rest and in transit. This ensures that, even if data are intercepted, they remain unreadable and secure. In the future, either a national ID card or a thumbprint could potentially be used to establish an SSI model. In our study, we collected mobile contact information and email addresses so that multi-factor authentication could be applied to verify the identity of individuals participating in the census. This reduced the risk of impersonation or duplicate entries. Privacy risks such as identify theft and data breaches still exist, even when strong encryption applied. There are a few strategies that might help in mitigating these risks, such as the following:* Zero-Knowledge Proofs (ZKP): It allows one party to prove to another that a statement is true without revealing any information beyond the validity of the statement itself. Implementing ZKP in a blockchain-based census system can enable individuals to verify their identity or other sensitive information without exposing the actual data. This approach is particularly valuable in census data collection, ensuring data privacy and security while maintaining accuracy [75; 76]. * Homomorphic Encryption: This form of encryption allows computations to be carried out on ciphered text, generating an encrypted result which, when decrypted, matches the result of operations performed on the plain text. It enables the processing of encrypted census data without needing to decrypt it, thus maintaining data privacy throughout the analysis phase [77; 78; 79]. * Private Smart Contracts: These are smart contracts that maintain the privacy of the contract's data and state. Implementing this could ensure that the census data collected and processed on the blockchain remain confidential and only accessible to authorized entities [80; 81]. * Self-Sovereign Identity (SSI): SSI is a digital identity that gives individuals control over the storage and management of their personal data. By incorporating SSI, individuals can manage their demographic data and consent to their use in the census. This not only empowers citizens but also enhances the security and accuracy of the census data, as individuals are more likely to provide accurate information if they retain control over them [82; 83; 84]. * Decentralized Identifiers (DIDs): DIDs are a new type of identifier that enables verifiable, self-sovereign digital identities. They can be used to create a secure and verifiable identity system for census data collection, ensuring that each individual's data are accurately linked to them without exposing personal information [85; 86]. With these strategies, a blockchain-based census system can effectively manage user identities while mitigating privacy risks, thus significantly strengthening the security and privacy aspects of the system.