Since inception, blockchain has earned significant attention due to its exclusive characteristics and advantages. It has changed the way the transactions are conducted by eradicating the role of third parties and promises to ensure trust among the participants. This technology is emerging as a potential solution to several issues but not without certain security vulnerabilities. In particular, protection of sensitive data is a more critical issue in the absence of a third party. This paper is aimed to report and share the state of the art of sensitive data protection in blockchain applications. The covered aspects include identification of sensitive data, existing techniques to protect sensitive data and to know how real time data compromised by security risks, attacks, threats and vulnerabilities concerning blockchain applications. This paper analysis the tools and techniques used in the past for protecting sensitive data and categorized them. On the basis of research and intuitive findings, methods and techniques are elaborated which can contribute in future in the designing a framework for protection of sensitive data in blockchain applications.

SummaryEvery transaction is made public and verified by a third party, and the transparency of blockchain applications leads to privacy leaks. Everyone can access the transaction, making it easier for network analysis to identify the user's identity, which is a major problem with the blockchain. Financial institutions have become hesitant to adopt blockchain technology; as a result, preventing its spread. To confirm that encryption and security are maintained for transactions in the blockchain, this research introduces a zero‐knowledge proof (ZKP) based transaction validation scheme. To increase the security of blockchain applications, the proposed lattice‐based blind ring signature (LBRS) scheme integrates blind and ring signatures and is applied to sensitive data. The data are encrypted using this encryption scheme before being stored with the transactional information in the blocks. The encrypted data is then stored in the blocks, which users can retrieve after verification. The encrypted data is then stored in blocks, which users can retrieve after verification. A verification scheme based on the ZKP is used to prevent unauthorized access and changes to the data. The proposed LBRS scheme meets the security analysis requirement. The performance of an LBRS scheme is compared to other relevant models in terms of execution time, encryption time, and decryption time. Overall, the results are more encouraging and reassuring than other relevant works of interest. Finally, this model provides better computational security and satisfies the requirements like correctness and security analysis.

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Blockchain, the technology behind most popular cryptocurrency Bitcoin and Ethereum, has attracted wide attention recently. It is the most emerging technology that has changed the financial and non-financial transaction system. It is omnipresent. Currently, this technology is enforcing banks, industries, and countries to adopt it in their financial, industrial, and government section. Earlier, it solved the centralize and double-spending problems successfully. In this chapter, the authors present a study of blockchain security issues and its challenges as well. They divided the whole chapter into two parts. The primer part covers a holistic overview of blockchain followed by the later section that argues about basic operations, 51% attack, scalability issue, Fork, Sharding, Lightening, etc. Finally, they mention an intro about its adaptation (financial or non-financial) in our 24/7 life and collaboration with fields like IoT.