Yes, you can use RSA algorithm to replace the Symmetric Key Cryptography (DES, AES) , but you should use longer key than Symmetric Key Cryptography (DES, AES) , and more calculations.

as u know the IoT devices have some constraints in power, processing data, memory, so because of these constraints i don't propose using RSA. you can use the lightweight version encryption than RSA like ECC or DTLS. ECC is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields.

This question is very interesting and I want to learn more about it. Please share some reference to your question (that would be very generous).

Yes you can but not recommended, because the RSA has a longer key length and many calculations that consume power, it is recommended to use ECC in a hybrid mode like ECDH because of the less key length and less calculations

Hi.

Yes it is possible to use a post-quantum cryptosystem like NTRU or RLWE.

Depending on how you store the key it can be even lesser secure using longer keys. Good crypto keys have close to perfect entropy which can be detected using statistical methods. The longer the key the easier to detect.

RSA (better ECC due to shorter keys) can be helpful when the decryption key can be entered later and is not part of the box from the very beginning. Process has a much bigger impact.

According to Kerckhoffs's principle, A cryptosystem should be secure even if everything about the system, except the key, is public knowledge. This means that your system must be secure with the secret key, whether using symmetric or asymmetric encryption.

Here are some things to say:

1- As mentioned in previous answers, other alternatives to RSA can be used to improve the efficiency of the system.

2- The security of asymmetric cryptosystems is not necessarily higher than symmetric ones. Especially because systems such as RSA, ECC, and DSA are not safe against quantum computers.

3- Asymmetric systems are usually used to eliminate the need for a pre-shared key. Otherwise, to reduce the time complexity, symmetric systems are much better candidates.

4- Before using encryption systems, you need to consider the weaknesses of such systems. For example, in NTRU, the private key may be easily found in the event of a mistake in updating the public key. In these particular cases, systems are not only safe against quantum computers but also vulnerable to classical personal computers.

5- Lastly, using symmetric-based asymmetric schemes may also be compatible with your goals.

Bellow excellent papers may be useful to you:

1- "Twenty Years of Attacks on the RSA Cryptosystem"

2- "Thirty Years of Attacks on the RSA Cryptosystem"

3- " Factoring RSA moduli with weak prime factors"

4- " Cryptanalysis of NTRU with two public keys"

5- " Post-Quantum Zero-Knowledge and Signatures from Symmetric-Key Primitives".