  In blockchain-based anonymous cryptocurrencies, due to their
tamper-resistance and transparency characteristics, transaction data are
initially required to be anonymous, with the help of various cryptographic
techniques, e.g., commitment schemes and zero-knowledge proofs. Also,
cryptocurrencies are different from existing anonymous messaging protocols
regarding the software architecture and the underlying security model. Due to
these differences, the sense of anonymity must be specifically defined for
anonymous cryptocurrencies, and the anonymity in each anonymous cryptocurrency
must be analyzed and evaluated based on the specific architecture model. In
this paper, we first propose a specific architecture model with three software
layers to anonymous cryptocurrencies. Next, we introduce definitions of
fundamental privacy properties (Pfitzmann's anonymity, unlinkability, and
pseudonymity) and comprehensively analyze each privacy property for each
architecture layer of anonymous cryptocurrencies to establish a privacy
evaluation policy for anonymous cryptocurrencies. Finally, we fairly compare
the privacy of current leading anonymous cryptocurrencies (e.g., Zerocash,
CryptoNote, and Mimblewimble) using the privacy evaluation policy.
