Hi guys, what would be the best approach if i will be creating AES encryption library for ios and android using Kotlin MP? Because my current idea is to accept the inputs from both platform as bytes and do the AES algorithm manually in the KMP which sounds exhausting. I just wanna know how would you guys tackle this. Thanks!

Always be wary of implementing your own encryption. You could try wrapping around some existing c implementation, or write a shared interface around separate platform-specific implementations.