I agree, it would be nice if they included the complete code, they provide code snippets in the various talks. Perhaps they are leaving it as an exercise for the viewer. It is a pretty trivial app, but you would need to track down the resources ;)
mikerichie
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You would need to run the Playgrounds app on MacOS 11 Big Sur or on an iPad running IOS 14 for the new APIs or features to be available.
Apple does not provide any APIs for blockchain creation, they do provide CryptoKit for cryptographic components. SwiftUI might be a good place to start to develop your User Interface as it can be used to both prototype and create your final product. For creating blockchains there are a number of open source projects such as hyperledger.org and corda.net that have libraries.