Following an update to its App Store review guidelines, Apple has explicitly halted the design and development of iOS applications which can be used for direct cryptocurrency mining. Still, off-device cloud-based mining is not affected by the changes.
Direct Cryptocurrency Mining is a No-Go
Even though there’s no official record of when the update in the developer’s guidelines took place, Apple made it pretty clear that it is directly targeting the prevention of cryptocurrency mining.
In its updated guidelines, Apple instructs any developer who wants to list his or her application on the App Store to refrain from producing software which runs unrelated background processes: