From: http://www.x2on.de/2010/02/01/tutorial-iphone-app-with-compiled-openssl-library/ and http://www.x2on.de/2010/07/13/tutorial-iphone-app-with-compiled-openssl-1-0-0a-library/
This is a tutorial for using self-compiled builds of the OpenSSL-library on the iPhone. You can build apps with XCode and the official SDK from Apple with this. I also made a small example-app for using the libraries with XCode and the iPhone/iPhone-Simulator. You can also download the precompiled OpenSSL-library (1.0.0d).
I have made an iOS 4.0 XCode Project with OpenSSL 1.0.0d Libaries. The examples uses the MD5 or SHA256-algorithm to calculate an md5 or sha256 hash from an UITextfield.