Kotlin Multiplatform has 0 support for cryptographic functions, and you have to annoyingly drop into each platform specific sources just to do things like sha 256.
Had the same issue with obtaining cryptographically secure random bytes from the system, which prompted me to create a library for it.
Needless to say, I bought the domain kotlincrypto.org and will be working towards building that out. Hopefully will have some basic hashing functions available Friday.
Idea:
A client you can run on your node that you can DM with a lightning invoice and it will pay it for you.
Will only accept DMs from a specified pubkey (yours)
Can "Uncle Jim" friends and family and set spending conditions for their Nostr pubkeys.