Take a look at http://opensource.apple.com/source/Security/Security-55471/l...specifically check the function SSLVerifySignedServerKeyExchange I leave the joy of spotting it to you. It is obvious and if you know c you'll see it(You don't need any knowledge of crypto). Here's a diff of that file from OS X 10.8.5 (Security-55179.13) to 10.9 (Security-55471): https://gist.github.com/alexyakoubian/915