Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Blockchain Privacy Through Merge Avoidance and Mixing Services: a
  Hardness and an Impossibility Result   Cryptocurrencies typically aim at preserving the privacy of their users.
Different cryptocurrencies preserve privacy at various levels, some of them
requiring users to rely on strategies to raise the privacy level to their
needs. Among those strategies, we focus on two of them: merge avoidance and
mixing services. Such strategies may be adopted on top of virtually any
blockchain-based cryptocurrency. In this paper, we show that whereas optimal
merge avoidance leads to an NP-hard optimization problem, incentive-compatible
mixing services are subject to a certain class of impossibility results.
Together, our results contribute to the body of work on fundamental limits of
privacy mechanisms in blockchain-based cryptocurrencies.

19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin