The post How CoinJoin Anonymity Can Be Undermined Using Clustering appeared on BitcoinEthereumNews.com.

Anonymity is the end goal when studying privacy, and it’s useful to think of de-anonymization as a game. We imagine an adversary with some access to information, and it tries to guess correctly who among a set of candidates was responsible for some event in the system. To defend against the adversary winning, we need to keep it guessing, which could either mean limiting its access to information or using randomness to increase the amount of information it needs to succeed. Many readers will be familiar with the game of “Guess Who?”. This game could be described as a turn-based composition of two instances of the more general game “twenty questions.” In “twenty questions,” you secretly choose an element from a given set, and your opponent tries to guess it correctly by asking you up to 20 yes-or-no questions. In “Guess Who?” both sides take turns playing against each other, and the first to guess correctly wins. The set of elements is fixed in “Guess Who?”, consisting of 24 cartoon characters with various distinguishing features, such as their hair color or style. Each character has a unique name that unambiguously identifies them. The answers to a yes-or-no question can be represented as a bit — zero or one. Twenty bits can express, in base 2, any whole number in the range 0 to 1,048,575, which is 2²⁰-1. If a set can be totally ordered, each element in the set may be indexed by its numbered position in the order, which uniquely identifies it. So, 20 bits can uniquely address one of just over a million elements. Although 2²⁰ is the maximum number of elements of a set that could be uniquely identified using just the answers to 20 yes-or-no questions, in real-world situations, 20 answers will often contain less information…

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Filed under: News - @ July 11, 2025 8:26 pm