The author explains why cryptography is not based on NP-complete problems, highlighting the importance of average-case hardness in cryptographic schemes. They use the example of the RSA problem to demonstrate how random instances of a problem must be difficult for cryptography to be secure. The author contrasts the complexity theorist’s definition of a hard problem with that of a cryptographer, emphasizing the need for problems that are hard in the average case. Despite some connections between average-case and worst-case hardness in lattice problems, encryption schemes based on NP-complete problems have not been successful.
https://blintzbase.com/posts/cryptography-is-not-based-on-np-hard-problems/