Possibly of interest to readers (but not directly competing) is securestore, our open-source, open-protocol, cross-language framework (cli tool + libraries) for securely storing secrets and programmatically retrieving them in production: https://neosmart.net/blog/securestore-open-secrets-format/

donet version: https://github.com/neosmart/SecureStore

rust version: https://github.com/neosmart/securestore-rs

(This one is production ready)