  Many storage customers are adopting encryption solutions to protect critical
data. Most existing encryption solutions sit in, or near, the application that
is the source of critical data, upstream of the primary storage system. Placing
encryption near the source ensures that data remains encrypted throughout the
storage stack, making it easier to use untrusted storage, such as public
clouds.
  Unfortunately, such a strategy also prevents downstream storage systems from
applying content-based features, such as deduplication, to the data. In this
paper, we present Lamassu, an encryption solution that uses block-oriented,
host-based, convergent encryption to secure data, while preserving
storage-based data deduplication. Unlike past convergent encryption systems,
which typically store encryption metadata in a dedicated store, our system
transparently inserts its metadata into each file's data stream. This allows us
to add Lamassu to an application stack without modifying either the client
application or the storage controller.
  In this paper, we lay out the architecture and security model used in our
system, and present a new model for maintaining metadata consistency and data
integrity in a convergent encryption environment. We also evaluate its storage
efficiency and I/O performance by using a variety of microbenchmarks, showing
that Lamassu provides excellent storage efficiency, while achieving I/O
throughput on par with similar conventional encryption systems.
