## 1 Introduction  
A national population and housing census is meant to collect comprehensive data on the demographics, individual characteristics, and living conditions within a country. These data are crucial for policymakers to make informed decisions regarding the economy, finance, healthcare, social benefits, import/export, education, and other sectors, ultimately driving a nation's development. The United Nations stipulates the necessity of a decennial census, a procedure conducted every ten years to accumulate data about the inhabitants of a jurisdiction [1]. Yet, shortcomings in the census system can substantially hinder a country's strategic planning and overall interests. The existing census systems are flawed, with data updates occurring only once every ten years, leading to a laborious and redundant process. This system often fails to protect the rights of minorities and marginalized communities against corrupt governments and influential individuals [2, 3]. Current census data collection methods encounter difficulties in enumerating elusive populations, often referred to as \"missing persons\". These individuals live in challenging situations, including unregistered buildings, non-compliant house extensions, shared residences, and concealed or mobile locations [2, 4, 5]. Deliberate efforts by certain minorities and undocumented immigrants to evade detection further complicate their inclusion in the census. The involvement of humans in data management introduces errors and potential leaks, prompting investigations into formal solutions which reduce human interaction to ensure more precise and secure outcomes. There have been instances of statistical ethnic cleansing and misrepresentation of minorities worldwide. The current system also struggles with transparency, data quality, and the protection of personally identifiable information (PII) [6]. These problems are exacerbated by external immigrants from war zones and internally displaced populations due to climate change, as the urgency for care and relief often takes precedence over data privacy and protection requirements. The scope of this paper is to investigate the use of a blockchain-based national population and housing census and address the issue of missing persons in census data by utilizing community-level datasets from non-governmental organizations (NGOs) to verify individuals' living conditions and addresses. This method provides a granular and accurate representation of population demographics, combining diverse datasets from various stakeholders to create a reliable source of truth. This contrasts with current government-based systems, which are often susceptible to corruption and political manipulation. Implementing a national population census on a blockchain is expected to provide inherent security, transparency, and immutability advantages, while adding societal value to record, monitor, forecast, and extrapolate a country's demographic dynamics and socio-economic activities. It bridges the gap between computer science, surveying, government data collection instruments, distributed ledgers, demographics, statistical models, and population censuses, fostering a multidisciplinary approach which combines ideas, business applications, technology, and governance frameworks. The result is a new supplementary implementation model for national censuses that enhances security, accountability, and transparency and addresses the challenge of missing people unaccounted for by traditional census methods. In this paper, Section 2 covers the methodologies followed in the enumeration process. Section 3 discusses the literature understanding of this topic based on our prior publication of a systematic literature review. Sections 4 and 5 cover the characteristics of blockchain, its implementation in the government sector, and related works in our research area. Section 6 highlights the core findings related to Pakistan's national census system (a case study). Section 7 covers a census architecture design based on Hyperledger Fabric.