# TrustShare: Secure and Trusted Blockchain Framework for Threat Intelligence Sharing
## 2 Background
### Blockchain Overview  
Blockchain, a unique and promising technology, has brought tangible changes to the cybersecurity field. The first appearance of blockchain was in 2008 regarding Nakamoto [12; 13], which was associated with the Bitcoin cryptocurrency and the digital financial sector. Fundamentally, blockchain was innovated to secure Bitcoin transactions and ensure transaction is received by the concerned person. Lately, it has demonstrated its validity, efficacy, and efficiency in various areas. As a result, it became extensively used in information systems and computer network security with its different applications. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Category** & **Description** & **Focus** & **Example** \\ \hline \multirow{2}{*}{Actionable Intelligence} & Specific, relevant, and timely & Directly applicable details for & Indicators of compromise (loCs); \\  & information for immediate threat & enhancing cybersecurity defenses. & specific vulnerabilities. \\ \hline \multirow{2}{*}{Tactical Intelligence} & In-depth insights into the techniques and procedures used by threat actors. & Understanding methods to adapt and & Analysis of attack patterns; tactics \\  & & refine security measures. & employed by threat actors. \\ \hline \multirow{2}{*}{Strategic Intelligence} & Broader long-term perspectives on & Assists in shaping the overall & Industry-specific threat landscapes; \\  & threat actors’ goals and motivations. & cybersecurity strategy by predicting & geopolitical influences on cyber \\  & & future threats. & threats. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cyber threat intelligence categories. Figure 2: Threat intelligence lifecycle involves data collection, analysis, and dissemination among trusted partners. Blockchain is a decentralized digital ledger that stores electronic records [14]. It basically works as a network of computers, or nodes, scattered among several devices, each of which maintains transactions and data. Blockchain relies heavily on nodes, which represent computers. Transactions undertaken during a certain period are organized into blocks, each with its own unique identification known as a hash. Each block includes the hash of the previous block [15]. A hash is the result of a cryptographic procedure that generates a fixed-size output from any amount of input data. The aforementioned procedure is irreversible. Transaction authentication in the blockchain includes cryptographic keys (public and private keys). When a transaction is requested, a block with the transaction is created and broadcast to the whole network. Before authorizing a transaction and adding a block to the chain, the network nodes must reach a consensus. The consensus method secures transaction acceptance by requiring a majority of nodes to verify the transaction. Notably, nodes participate in mining, which is the process of solving complicated mathematical problems (algorithms) in order to verify transactions. This procedure, known colloquially as proof of work, emphasizes the decentralized and secure character of blockchain networks. Currently, PoW is the most widely used mechanism for mining. However, PoW requires substantial computing power and therefore uses considerable amounts of energy, a notable drawback. To solve this issue, another mining mechanism, proof of stake (PoS), is becoming popular. PoS provides faster transactions and uses less energy during mining [16]. Consequently, blockchain provides a secure and trusted method as it has gained a good reputation among existing security techniques. There are key features that make blockchain have great potential to be valid for various security applications, such as immutability and transparency, traceability, and providing a trusted method whereby verification and validation are conducted without the need for trusted signers or third parties.