Asymmetric vs. Symmetric key cryptography

[imin67]

Hi folks,

This is sort of a general question. So the thing is I wrote an exam in a security related subject. One of the question required us to explain the pros and cons of Asymmetric and Symmetric key cryptography. Part of my answer included this statement:
Asymmetric key cryptography is more secure when the communication channel is insecure and usually used for the exchange of symmetric keys as it is computationally expensive.

After the results came out and we had a review session, the corrector mentioned that the term "more secure" is wrong and therefore a deduction was made on that one.

I'm still not convinced by his answer, as I think this is the whole point of asymmetric cryptography. If I'm wrong, could somebody try to shed some light on why and provide a correct answer instead? Thanks a lot in advance.

Cheers,
imin

 

[Yami]

Was the corrector arguing that asymmetric was NOT more secure, or was their argument that "more secure" is an invalid concept in that something is either secure or it is not?

If it's the former, they are mostly wrong - asymmetric IS typically more secure than symmetric. But keep in mind that a badly-implemented asymmetric system might be less secure than a well-implemented symmetric system.

They're also wrong if it's the latter as security is a spectrum.