Bitcoin and many other similar Cryptocurrencies have been in existence for over a decade, prominently focusing on decentralized, pseudo-anonymous ledger-based transactions. Many protocol improvements and changes have resulted in new variants of Cryptocurrencies that are known for their peculiar characteristics. For instance, Storjcoin is a Proof-of-Storage-based Cryptocurrency that incentivizes its peers based on the amount of storage owned by them. Cryptocurrencies like Monero strive for user privacy by using privacy-centric cryptographic algorithms. While Cryptocurrencies strive to maintain peer transparency by making the transactions and the entire ledger public, user privacy is compromised at times. Monero and many other privacy-centric Cryptocurrencies have significantly improved from the original Bitcoin protocol after several problems were found in the protocol. Most of these deficiencies were related to the privacy of users. Even though Bitcoin claims to have pseudo-anonymous user identities, many attacks have managed to successfully de-anonymize users. In this paper, we present some well-known attacks and analysis techniques that have compromised the privacy of Bitcoin and many other similar Cryptocurrencies. We also analyze and study different privacy-preserving algorithms and the problems these algorithms manage to solve. Lastly, we touch upon the ethics, impact, legality, and acceptance of imposing these privacy algorithms.

翻译：比特币及众多类似加密货币已存在十余年，其主要特点在于支持去中心化、伪匿名化的账本交易。许多协议改进与变革催生了具有独特属性的加密货币变体。例如，Storjcoin作为一种基于存储证明的加密货币，根据节点拥有的存储空间量进行激励。门罗币等加密货币则通过采用隐私核心的加密算法来保障用户隐私。尽管加密货币通过公开交易与完整账本维护对等透明度，但用户隐私时常因此受损。在比特币原始协议发现多项问题后，门罗币及众多隐私优先型加密货币已对其进行了显著改进。这些缺陷大多涉及用户隐私。即便比特币宣称提供伪匿名用户身份，仍有多种攻击成功实现了用户去匿名化。本文系统梳理了已成功突破比特币及同类加密货币隐私保护的知名攻击方法与分析技术，同时探究了不同隐私保护算法及其解决的特定问题。最后，我们探讨了应用这些隐私算法的伦理影响、法律效力与社会接受度。