I couldn’t think of a better site for it, but seems no question on the topic so far.
If they are, to what extent or in what regards?
Generally they are not, unless they are explicitly about the cryptographic algorithms used to implement the NFT. If they are about the general security you could ask on IT Security. If they are about the other algorithms used, you could ask this same question e.g. on the Meta of Computer Science.
In principle if they are more about how cryptography is integrated into NFT then they I guess they might be on topic; this is a grey area. But please note that I'm not aware of many NFT experts on this Q/A site, so your reach may be minimal.
For a bit more information on how these things are generally handled if there is no SE specific site, see the Q/A on cryptocurrency & blockchain on Meta.
On-topic (probably): Handshake protocols and secure communication between NFT endpoints
Off-topic: Physical characteristics, electro-magnetic encodings, general interchange format.
Goto Security.SE: Authentication, authorization, access-control.
Made a pullet-list for clearer presentation