  Trusted execution environments (TEEs) are an integral part of modern secure
processors. They ensure that their application and code pages are confidential,
tamper proof and immune to diverse types of attacks. In 2021, Intel suddenly
announced its plans to deprecate its most trustworthy enclave, SGX, on its 11th
and 12th generation processors. The reasons stemmed from the fact that it was
difficult to scale the enclaves (sandboxes) beyond 256 MB as the hardware
overheads outweighed the benefits. Competing solutions by Intel and other
vendors are much more scalable, but do not provide many key security guarantees
that SGX used to provide notably replay attack protection. In the last three
years, no proposal from industry or academia has been able to provide both
scalability (with a modest slowdown) as well as replay-protection on generic
hardware (to the best of our knowledge). We solve this problem by proposing
SecScale that uses some new ideas centered around speculative execution (read
first, verify later), creating a forest of MACs (instead of a tree of counters)
and providing complete memory encryption (no generic unsecure regions). We show
that we are 10% faster than the nearest competing alternative.
