I want to achieve something like

tar -c directory | openssl foo > encrypted_tarfile.dat

I need the openssl tool to use public key encryption.

I found an earlier question about symmetric encryption at the command promt (sic!), which does not suffice. I did take a look in the openssl(1) man page and only found symmetric encryption. Does openssl really not support asymmetric encryption?

Basically many users are supposed to create their encrypted tar files and store them in a central location, but only few are allowed to read them.