thanks, yes, that's why I'm doing inside the engine as well.
The question was regarding the library that my engine links against that in turn uses libcrypto again.
That linked library uses the EVP methods with the "default"-engine, which is however set from the surrounding application.
I guess it's a similar question to when an application links against liba.so and libb.so and both use openssl internally but set different default engines. How can you prevent them from interfering with each other ?