  As cache-based side-channel attacks become serious security problems, various
defenses have been proposed and deployed in both software and hardware.
Consequently, cache-based side-channel attacks on processes co-residing on the
same core are becoming extremely difficult. Most of recent attacks then shift
their focus to the last-level cache (LLC). Although cache partitioning is
currently the most promising defense against the attacks abusing LLC, it is
ineffective in thwarting the side-channel attacks that automatically create
eviction sets or bypass the user address space layout randomization. In fact,
these attacks are largely undefended in current computer systems.
  We propose Remapped Cache Layout (\textsf{RCL}) -- a pure hardware defense
against a broad range of conflict-based side-channel attacks. \textsf{RCL}
obfuscates the mapping from address to cache sets; therefore, an attacker
cannot accurately infer the location of her data in caches or using a cache set
to infer her victim's data. To our best knowledge, it is the first defense to
thwart the aforementioned largely undefended side-channel attacks .
\textsf{RCL} has been implemented in a superscalar processor and detailed
evaluation results show that \textsf{RCL} incurs only small costs in area,
frequency and execution time.
