heimdal  7.7.0
About: Heimdal is a free implementation of Kerberos 5 (a system for authenticating users and services on a network).
  Fossies Dox: heimdal-7.7.0.tar.gz  ("inofficial" and yet experimental doxygen-generated source code documentation)  

EVP - generic crypto interface

See the library functions here: EVP generic crypto functions

EVP Cipher

The use of EVP_CipherInit_ex() and EVP_Cipher() is pretty easy to understand forward, then EVP_CipherUpdate() and EVP_CipherFinal_ex() really needs an example to explain example_evp_cipher.c .