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The blockchain research team at University College London (UCL) has not slowed down, recently releasing a study on Zcash. The study suggests that although Zcash allows users to transact anonymously, there are methods to reduce its anonymity. Zcash has publicly responded to these research findings.
According to UCL researchers George Kappos, Haaroon Yousaf, Mary Maller, and Sarah Meiklejohn, while Zcash does offer anonymity in transactions, it also provides transparent transaction features. When tokens are transferred from an "unshielded" address to a "shielded" address and then back to an "unshielded" address, it significantly reduces anonymity.
Zcash's design involves two types of addresses: t-address (short for "t"), where wallet balances and transaction content are "unshielded," and z-address (short for "z"), where wallet balances and transaction content are "shielded." Transactions between t-addresses are transparent, similar to Bitcoin transactions, showing complete details of content and time. Transactions between z-addresses only display time and miner fees.
However, transferring between t and z addresses provides an opportunity to gather transaction information from z addresses. The research experiment describes: "With this relatively simple probing strategy, anonymity is reduced by 69.1%." In the experiment, they transferred tokens from t to z and then extracted them from z to t.
This method is not foolproof, as the study notes: "This method will be significantly compromised if the behavior of the creator of anonymous transactions in the pool is irregular." However, if the creator of anonymous transactions consistently extracts a certain amount at fixed time frequencies, it becomes easy to identify the user they are transacting with. The research indicates that this is due to the need for anonymous transactions to go through Zcash's shielded pool. |
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