I was reading this [paper](https://dergipark.org.tr/en/download/article-file/4060550) that claims to "combine metaverse with blockchain", but I have a hard time understanding their use of primitives. On page 4 they first generate the key-pairs (not sure which scheme?):
https://preview.redd.it/zpkop4rklife1.png?width=672&format=png&auto=webp&s=8cef80acf6bafc73585f06bb71a8a565fea02afb
Then the patient uses his/her private key to sign the data, and then the hospital encrypts it (page 5):
https://preview.redd.it/cbur2iezlife1.png?width=691&format=png&auto=webp&s=ac36069b1d42256c93ab9d1d7aaa3e18fc195691
So I'm guessing (pk0, pk1) is probably from Ed25519 but (ak0, ak1) may be from X25519. The patient data is then encrypted using ak0, but isn't that something you aren't supposed to do? The paper doesn't mention the size constraints on patient data either.
It then says that:
>The newly generated data has to be validated before they can be added to the blockchain. These data are validated by the admin (doctor, pathologists, radiologists) following the process depicted in figure 5 using the admin private key ak1.
But figure 5 doesn't mention ak1:
https://preview.redd.it/bn0ei7e8oife1.png?width=699&format=png&auto=webp&s=dfec3ff0b2a196be1bc860067ca2b41072b4e014
What was the point of ak\* anyway given that the hospital is the one encrypting the data in the first place? Am I missing something?