Tumbling Down the Stairs: Exploiting a Tumbler's Attempt to Hide with Ordinary-looking Transactions using Wallet Fingerprinting

The privacy of Bitcoin transactions is a subject of ongoing research
from parties interested in enhancing their security, as well as those
seeking to analyze the flow of funds happening in the network. Various
techniques have been identified to de-obfuscate pseudonymity, e.g.,
heuristics to cluster addresses and transactions, automatic tracing of
transaction chains based on usage patterns/features that may reveal
common ownership. These techniques gave rise to services that attempt to
make these techniques unreliable with specific forms of behavior.
Examples of such behavior include using one-time addresses or
transactions with multiple participants. Centralized services employing
these behavior patterns, commonly known as tumblers or mixers, offer
customers a way to obfuscate their financial flows. In turn, new
approaches have been proposed in recent scientific literature to exploit
the way the mixers operate in order to gain insight into the underlying
financial flows. In this paper, we analyze some of these approaches and
identify challenges in the context of their application to a particular
modern mixing service -- Anonymixer. Furthermore, based on this
analysis, we propose a novel approach for identification of addresses
involved in mixing with capability to distinguish between
depositing/withdrawing parties and mixer inner addresses. The approach
utilises wallet fingerprints, which we have extracted using statistical
measurements of mixer's behavior. An internally developed tool
implementing the proposed techniques automates the deobfuscation process
and outputs individual money transfers.