  In this work we discuss the resistance of atomic pattern algorithms for
elliptic curve point multiplication against simple side channel analysis
attacks using our own implementation as an example. The idea of the atomicity
principle is to make kP implementations resistant against simple side channel
analysis attacks. One of the assumptions, on which the atomicity principle is
based, is the indistinguishability of register operations, i.e. two
write-to-register operations cannot be distinguished if their old and new data
values are the same. But before the data can be stored to a register/block,
this register/block has to be addressed for storing the data. Different
registers/blocks have different addresses. In praxis, this different and key
dependent addressing can be used to reveal the key, even by running simple SCA
attacks. The key dependent addressing of registers/blocks allows to reveal the
key and is an inherent feature of the binary kP algorithms. This means that the
assumption, that addressing of different registers/blocks is an
indistinguishable operation, may no longer be applied when realizing kP
implementations, at least not for hardware implementations.
