The Intel Security Guard Extensions (SGX) architecture enables the abstraction
of enclaved execution, using which an application can protect its code and data
from powerful adversaries, including system software that executes with the
highest processor privilege. While the Intel SGX architecture exports an ISA
with low-level instructions that enable applications to create enclaves, the
task of writing applications using this ISA has been left to the software
community.

We consider the problem of porting legacy applications to SGX enclaves. In the
approximately four years to date since the Intel SGX became commercially
available, the community has developed three different models to port
applications to enclaves—the library OS, the library wrapper, and the
instruction wrapper models.

In this paper, we conduct an empirical evaluation of the merits and costs of
each model. We report on our attempt to port a handful of real-world
application benchmarks (including OpenSSL, Memcached, a Web server and a Python
interpreter) to SGX enclaves using prototypes that embody each of the above
models. Our evaluation focuses on the merits and costs of each of these models
from the perspective of the effort required to port code under each of these
models, the effort to re-engineer an application to work with enclaves, the
security offered by each model, and the runtime performance of the applications
under these models.