## 4 Experiments and Results
### Time-Based Hash Storage  
In the time-based strategy, the blockchain module selected data at fixed time intervals to form a transaction batch. We set a time interval of 10 min to select critical data, and a time interval of 60 min to select the complete record of closed incidents, which comprises all the ordinary data. Subsequently, the transaction batch was processed using the SHA-256 hash function, and the resulting data hash was submitted to the DataHashStorage smart contract for permanent storage on the blockchain. The contract was deployed on the Ethereum Sepolia testnet, and is accessible at the following address: 0\(x2a5A789 bbeE29c8f6c824476a82D3 aE787b6d1F5\). The contract code, along with the complete transaction history, is accessible on the corresponding Sepolia Etherscan page \begin{table}
\begin{tabular}{l l} \hline \hline
**Field Name** & **Field Description** \\ \hline Incident\_Datetime & Incident creation in the dispatch system \\ First\_Assignment\_Datetime & First unit is assigned to the incident \\ First\_Activation\_Datetime & First unit is enroute to the incident location \\ First\_On\_Scene\_Datetime & First unit arrives at the incident location \\ First\_To\_Hosp\_Datetime & First unit is enroute to the hospital \\ First\_Hosp\_Arrival\_Datetime & First unit arrives at the hospital \\ Incident\_Close\_Datetime & Incident closes in the dispatch system \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Name and description of key fields in the incident dispatch dataset used to identify critical data within the proposed approach. \begin{table}
\begin{tabular}{l l c c} \hline \hline
**Field Name** & **Description** & **Sample Entry 1** & **Sample Entry 2** \\ \hline CAD\_ID & Unique incident identifier & 50011297 & 50132272 \\ Call\_Type & Type of emergency call & INJURY & OTHER \\ Severity\_Code & Call priority level & 5 & 6 \\ Disposition\_Code & Final incident outcome & CANCEL & 90 \\ Borough & Incident borough & BRONX & QUEENS \\ Zipcode & Incident zip code & 10467 & 11369 \\ Police\_Precinct & Incident police precinct & 47 & 115 \\ Standby\_Indicator & Indicates if units were on standby & N & Y \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Representative subset of fields categorized as ordinary data in the incident dispatch dataset, with descriptions and example values. The full list of fields and descriptions is available on the dataset homepage [23]. ([[https://sepolia.etherscan.io/address/0x2a5a789](https://sepolia.etherscan.io/address/0x2a5a789) bebee29c8 fc824d76a82d3 ae787b6d1f5]([https://sepolia.etherscan.io/address/0x2a5a789](https://sepolia.etherscan.io/address/0x2a5a789) bebee29c8 fc824d76a82d3 ae787b6d1f5), (accessed on the 7 February 2025)). The DataHashStorage contract implements the function storeDataHash(bytes32_dataHash), which accepts the SHA-256 hash as input and stores it in an internal mapping. This mapping persistently associates each hash with the timestamp of the block in which it was included, consuming some portion of the storage space in the Sepolia network. We ran extensive experiments to evaluate the transaction fees and the time required to write hashes to the blockchain. In total, we executed 2050 transactions on the Sepolia network, spanning different days of the week and different times of the day. The success rate for executing transactions was 100%. Figure 3 presents a histogram showing the distribution of block confirmation times. Data distribution analysis revealed that block confirmation times tend to cluster. To identify the time intervals corresponding to each cluster, we used the kernel density estimate (KDE) inferred from the data. Specifically, we extracted the relative minima of the multimodal KDE plot (see Figure 3) and observed the corresponding x-axis values as the boundaries for each time cluster. Table 4 presents reference metrics and count values for each cluster. To assess the costs associated with hash writing, we analyzed the transaction receipts and calculated the fees in Gwei (\(1\) Gwei = \(1\times 10^{-9}\) ETH).