Security Concerns in BlockchainsWhile blockchains have been applauded as effective replacements for traditional data storage systems, through their transparent approach, they have introduced a new variety of security risks, as will be demonstrated in this section. The transparency of blockchains is an example of these risks. One of the most glaring security vulnerabilities that Bitcoin, a currency implementation of the blockchain, presents is the unencrypted nature of its wallet. This is because the nature of its openness could attract malicious individuals with the resources to hack the wallet. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay As implausible as it may seem, a Bitcoin-like blockchain implementation known as Ether was targeted in 2016 and defrauded of $50 million (ENISA). Additionally, data wallets can be accessed via a backup of the previous version of the wallet (Kiviat). The use of Apple Time Machine, a facility that allows such backups to empty current data wallets through the use of backups, allows hackers to acquire personal data in a blockchain implementation. This is because changing a wallet password does not reflect the cancellation of previous passwords (Sompolinsky and Zohar). Furthermore, Interpol also demonstrated in 2015 how Bitcoin could be subverted through the introduction of uncorrelated data into an existing transaction (Zyskind and Nathan). Another security concern presented by blockchains is consensus hijacking, also known as a Sybil attack. Blockchains prevent monopolistic control of the network so as to add security measures. However, an attacker using the Sybil attack and with more than half the power of the network can modify blockchain transactions by making the transactions appear to be valid (Bissias, Ozisik, and Levine) (ENISA). With such monopolistic control, the attacker may have the power to reverse the transactions sent, exposing other users to the risk of double spending attacks. It may even prevent the user's transactions from being confirmed, thus limiting their power to access their favorite data. Once connected to the attacker, users can be trapped by connecting only to Sybil nodes, thus predisposing them to attacks such as double-spending. Blockchain sidechains represent the other source of security vulnerabilities in the technology. Sidechains are vulnerable when used for pegging (ENISA). This happens when information between one section of a blockchain and another is exchanged through a proxy address that reports the actual address of the section carrying out the transaction. If a user of a chain exchanges information with a fraudulent proxy address of a non-existent blockchain section, there is no way to recover the information (Kiviat). Furthermore, other users transacting with the fraudulent sidechain will realize its malice and download their information to the parent chain, thus stressing the entire system. Another security issue concerns authorized chains. In such regulated chains, the blockchain regulator can be manipulated to inadvertently direct a hack. This is because the regulator has extra capacity in the network. In such scenarios, the security risks of the chain are equivalent to those of centrally administered networks (ENISA). Another security concern would be the relevance of distributed denial-of-service attacks since blockchains themselves are simply distributed ledgers. There is one.