  A common misconception among blockchain users is that pseudonymity guarantees
privacy. The reality is almost the opposite. Every transaction one makes is
recorded on a public ledger and reveals information about one's identity.
Mixers, such as Tornado Cash, were developed to preserve privacy through
"mixing" transactions with those of others in an anonymity pool, making it
harder to link deposits and withdrawals from the pool. Unfortunately, it is
still possible to reveal information about those in the anonymity pool if users
are not careful. We introduce Tutela, an application built on expert heuristics
to report the true anonymity of an Ethereum address. In particular, Tutela has
three functionalities: first, it clusters together Ethereum addresses based on
interaction history such that for an Ethereum address, we can identify other
addresses likely owned by the same entity; second, it shows Ethereum users
their potentially compromised transactions; third, Tutela computes the true
size of the anonymity pool of each Tornado Cash mixer by excluding potentially
compromised transactions. A public implementation of Tutela can be found at
https://github.com/TutelaLabs/tutela-app. To use Tutela, visit
https://www.tutela.xyz.
