## 4 BFS Technological Stack--Dual-Blockchain Framework  
The BFS system operates within an economic ecosystem characterised by a complex network of diverse business entities interconnected through business transactions. These transactions, essential for transferring monetary value through digital funds or tokenised assets, occur across the BFS ecosystem via wallet addresses, impacting each entity's monetary stance. The BFS system's technological framework introduces a novel dual-blockchain architecture, uniquely merging the distinct architectural elements of Bitcoin and Corda. This design not only automates the execution of transactions and accounting processes through innovative business and accounting transaction smart contracts but also standardises and automates the capture and integration of economic activities into a cryptographically verifiable accounting record for each entity. Moreover, the dual-blockchain setup enables the BFS system to operate effectively in a multi-blockchain environment, addressing critical trade-offs between accountability and privacy while securely sharing sensitive financial information. This ensures that the BFS architecture supports robust financial reporting while upholding the confidentiality and integrity of the data and participant privacy. First, the traditional \"Bitcoin\" [10] blockchain framework is adapted to design and implement the BFS filing history data structure utilised to store the financial statements of an entity (see Figure 1). This decision is motivated by the guarantee of this data structure to maintain a verifiable, tamper-proof, and cryptographically linked chronology of events within it. The BFS system is designed to handle the transformation of raw economic data into a format suitable for financial reporting, as follows:  
* Economic data generated from completed business transactions are transformed into accounting data, anonymized, classified, aggregated, and then packaged into financial statement reports. * These reports are stored in a traditional chain of cryptographically linked blocks within a permissioned blockchain data structure--the filing history. * This separate filing history blockchain is owned and distributed among the members of entities, such as business owners, accountants, employees, and so on. * Additionally, access permissions to this ledger can be modified and extended to qualified external stakeholders, such as other controlling entities (e.g., shareholders), or government bodies for regulatory or tax purposes. Serving as a filing history, this blockchain ledger is utilised as a tamper-proof financial reporting tool for documenting the financial health and trajectory of the business. However, in the traditional Bitcoin blockchain architecture, every peer participating in the network receives and processes every transaction ever conducted. Despite Bitcoin's architecture being known for ensuring participant anonymity, its broadcast communication method raises ongoing concerns regarding the privacy of business-sensitive transactional data. To address the critical challenge of ensuring transactional privacy while providing traceability for compliance or validation and transparency, the BFS system's design incorporates specific components of the Corda architecture [11], such as the point-to-point messaging of Corda's _Flow Framework_[11], and business transaction registers inspired by Corda's _Transaction Volts_[11]. These components are illustrated in Figure 2.  
* Corda's _Flow Framework_[11] ensures that sensitive transactional data are only transmitted between the parties relevant to the transaction, thereby remaining confidential between them and safeguarding business-sensitive information. * Corda's _Transaction Volt_[11] is implemented as a _business transaction register_ for each BFS entity. It serves as an application-local off-ledger repository that stores all business transactions (see Figure 2) in their \"raw state\", untransformed and ready for accounting processing and future validation if requested.