All, I can reliably core dump kotlin-native with this code: https://gist.github.com/anonymous/273e1a4e01daece84e48523da9dc82a8

did you try Valgrind on your program? It it very helpful tool for problems like this one.

Might it be, because you try to decode encrypted (read: random) data as UTF8? Do you still get that core dump if you comment out

var contentAsString = kotlin.text.fromUtf8Array(contents!!, 0, contents!!.size)

This makes sense, actually. Data in strings are intended to be valid utf8, and if they are not - exception shall be thrown (it’s a bug that it didn’t, although). But why you need to keep binary data in string? ByteArray is intended for that purpose.