Data register analysis

THIS SECTION IS NOT NORMATIVE

This section outlines the technical reasons for choosing Bitcoin SV, including relevant cost and security considerations.

6.1 Distributed Ledger Technology

Between 2017 and 2018, three distinct blockchain protocols emerged from Bitcoin's original protocol, sharing a history that dates to the genesis block. These are BTC, BCH, and BSV (Bitcoin SV). The BSV Blockchain ledger is a distributed platform that provides scalability, transparency, immutability, and efficient data consumption. Data can be published on the blockchain and retrieved within blockchain transactions.

Bitcoin SV typically produces blocks larger than 1GB, with the maximum recorded block size being 4 GB [3], and it supports a high transaction throughput of up to 5,100 blockchain transactions per second (tps) [4]. It accommodates large transaction sizes, with a record of a 42MB transaction [3] and has a default maximum script size of 500kB [3]. It also includes a complete set of opcodes and supports big integer arithmetic in-script [3]. Previously, we presented a solution based on the Bitcoin SV protocol for blockchain transactions, which can be easily adapted to any UTXO-based blockchain. illustrates a simplified schematic of a Bitcoin transaction. This transaction fee is the lowest among Proof of Work (PoW) blockchains [3].

6.2 Why not others? Ledger Comparison Analysis

Given the project's requirements, a Proof of Work (PoW), public, and permissionless blockchain was deemed necessary. PoW blockchains record cumulative PoW directly on the blockchain, making the data structure statistically resistant to attacks or modifications. BTC was excluded due to high transaction fees and a limited block size. Apart from Bitcoin SV, the remaining options were:

• BCH: A UTXO- PoW ledger with a maximum block size of 32MB. Although BCH has a higher transactions per second (TPS) rate than BTC, its transaction processing remains limited and while transaction fees are lower in average than BTC, they are still relatively high for the needs of this project.

• Ethereum (ETH): Previously a PoW ledger, now using Proof of Stake (PoS) as its consensus mechanism. All statements and data refer to ETH before this change. ETH is an account-based PoW ledger with an integrated smart contract layer that maintains a global state, posing scalability challenges [3]. The new adopted consensus mechanism allows ETH to process block faster than BTC and BCH and BSV. The transaction structure of an Ethereum will request, most likely to utilise a token protocol to store and monitor the DID Document. ERC-20, their most adopted token protocol overage transaction fee remains considerable large for the purpose of this project and as the complexity of the smart contract increases, so does the gas fee. ETH has the highest average transaction fees among blockchains.

• Private ledgers, such as Hyperledger, were not considered since solutions built on these ledgers incur higher costs for implementation, maintenance, transaction fees and conventionally single authorities running the infrastructure

Our solution requires high-volume transaction processing at low cost, as well as maintaining data integrity over time and across parties involved. Immutability and alteration records should be enforced by an independent process: the consensus mechanism. Additionally, it does not require the execution of any programmatic function at the miner level, avoiding execution costs in transaction fees. Lastly in BSV there’s the 'first-seen rule' which means that miners will not accept a double-spend before block publication even for a higher fee if a miner receives a transaction, they verify it is correct, then accept it as valid. This means they will not accept a double-spend of the same input. Then add the transaction in the mempool. It may appear in the next block, or the block after. For these reasons, we decided to implement the solution using Bitcoin SV, benefiting from its scalability, low cost, and data integrity provided by PoW.