The current situation of the crypto implementation of OpenSSH as shipped by Apple in OS X 10.9 is a real mess. Continuing their push in favor of Common Crypto and their deprecating of libcrypto (OpenSSL) they implemented in their version of OpenSSH a new crypto module compatible with OpenSSL's interface but targetting the Common Crypto library instead. However this implementation seems currently incomplete due to limitations of Common Crypto and as a result they also have embedded fallbacks on big chunks of OpenSSL code.

A concrete shortcoming is that there is actually no elliptic curve support, thus it is not possible to generate EC keys and use ECDSA signatures for authentication.