Yes, here's an article stating that "SgxSpectre Attack Can Extract Data from Intel SGX Enclaves".
According to researchers, SgxSpectre works because of specific code
patterns in software libraries that allow developers to add SGX
support to their apps. Vulnerable SGX development kits include the
Intel SGX SDK, Rust-SGX, and Graphene-SGX.
Academics say an attacker can leverage the repetitive code execution
patterns that these SDKs introduce in SGX enclaves and watch for small
variations of cache size. This is a classic "side-channel attack," and
is quite effective.
However, Intel stated that an update for the Intel SGX SDK that adds SgxSpectre mitigations will be released on March 16, 2018.
Also, Here's a research paper that does some theoretical analysis on compromising a blockchain network using SgX and finally states that "Yes, it might be possible".
The title of this paper is "On Security Analysis of Proof-of-Elapsed-Time (PoET)". I'm adding relevant snips of the paper to ensure that in case dead links occur, at least the summary of what they say is available in this post.
The brief of this paper states that
"To fulfil this gap, we develop a theoretical framework for evaluating
a PoET based blockchain system, and show that the current design is
vulnerable in the sense that an adversary can jeopardize the
blockchain system by only compromising Θ(log log n/ log n) fraction of
the participating nodes, which is very small when n is relatively
Based on our theoretical analysis, we also propose methods to mitigate
They go on to summarise that there are ways to mitigate these problems.
However, it is important to note that this paper does not mention a concrete method to compromise the safety of the PoET algorithm running in an SGX enclave and merely states that
"SGX and other trusted computing technologies are not 100% reliable.
Especially, they may be vulnerable to sophisticated adversaries with
necessary resources and skillsets."
But given the SGXSpectre attack, it is not an academic question but a practical one ....
UPDATE: Here's an excellent video titled "34C3 - Microarchitectural Attacks on Trusted Execution Environments" where Keegan Ryan
explains in great detail about how TEE attacks are performed. This is absolute gold for a person interested in defending against security breaches.
TLDR: Yes, it is indeed possible to compromise the PoET algorithm (SGXSpectre attack) as also by compromising a small fraction of the participant nodes. There are also some ways to mitigate if not resolve this issue (SGX SDK Patch, other approaches).