While seeking out for questions for (pre-quantum) public-key cryptography, I find that the questions being asked are variatiful. Askers' confusion can come from anywhere, and lack commonality.
Despite this, I believe the main cause is probably novices didn't properly grasp the purpose and meaning of public-key encryption, key exchange, digital signature, and sometimes other minor functionalities of PKC.
The few questions that I think has the widest audience are:
- ECDSA vs ECIES vs ECDH
- Why is public-key encryption so much less efficient than secret-key encryption?
- What is the point of digital signatures if confidentiality is violated?
- Why is asymmetric cryptography bad for huge data?
- Security strength of RSA in relation with the modulus size
- Can we find an archetypal textbook RSA question for here?
- Why do public keys need to be validated?
- What are the differences between a digital signature, a MAC and a hash?
- Digital signatures are !!NOT "encrypt" with private keys!!