Insecure private-key encryption I am learning about crytography and the differences between the public and private keys encryption examples and I was wondering if it is possible to have a private key encryption scheme that is completely insecure? I have not been able to find what that could look like but I'm curious? Or is this not possible? Is the encryption scheme always secure with private keys?
Any encryption scheme can be insecure if the key space is small enough.

For example, you could perform encryption with an 8 bit RSA key.  For a key of that size, it's trivial to determine the private key given the public key.