[PoC] run SQL over ciphertext

Hi all,

We have developed an extension, allowing PostgreSQL to run queries over
encrypted data. This functionality is achieved via user-defined functions
that extend encrypted data types and support commonly used expression
operations. Our tests validated its effectiveness with TPC-C and TPC-H
benchmarks. You may find the code here: https://github.com/SJTU-IPADS/HEDB.

This PoC is a reimplementation fork while collaborating with a cloud
database company; the aim is to enable their DBAs to manage databases
without the risk of data leaks, *meeting the requirements of laws such as
GDPR.*

I am wondering if anyone thinks this is a nice feature. If so, I am curious
about the steps to further it mature and potentially have it incorporated
as a part of PostgreSQL contrib.

Best regards,
Mingyu Li