Apple deprecated and then discontinued OpenSSL for its platforms and OS some years ago, leaving us with access to cryptography only through the Security framework. Unless, of course, you want to do some nasty hacks with custom built openssl libraries.
Unfortunately, the Security framework is not well documented, isn't specially developer friendly, and has not been thought to interact with 3rd parties, such as external servers making use of standard public key infrastructures and libraries such as OpenSSL.
However, nowadays, it's a common requisite for our apps to interact with secure backends and RESTful APIs making use of asymmetric cryptography, KPIs or public key systems. In this presentation, I will explain how to make your iOS application interact with these external public key infrastructures, importing keys from external entities (probably generated via OpenSSL) and exporting the keys generated at the device so they can be used in signature and verification operations externally.
Recorded and produced live by Stefan Völker.