  Since the creation of Bitcoin, transaction tracking is one of the prominent
means for following the movement of Bitcoins involved in illegal activities.
Although every Bitcoin transaction is recorded in the blockchain database,
which is transparent for anyone to observe and analyse, Bitcoin's pseudonymity
system and transaction obscuring techniques still allow criminals to disguise
their transaction trail. While there have been a few attempts to develop
tracking methods, there is no accepted evaluation method to measure their
accuracy. Therefore, this paper investigates strategies for transaction
tracking by introducing two new tainting methods, and proposes an address
profiling approach with a metrics-based evaluation framework. We use our
approach and framework to compare the accuracy of our new tainting methods with
the previous tainting techniques, using data from two real Bitcoin theft
transactions and several related control transactions.
