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Code and documentation

In the next few sections, we'll discuss some examples of EVP code.

Using the same structure as for the PKCS examples, we'll first define some general setup and cleanup functions, then some specific signing/verification functions, and finally we'll tie it all together in a calling main function. At every defined function, we'll reflect a bit on why we do what we do there, and note some other areas that might be of interest to the application developer.

Before you dive in, you might want to skim the documentation for OpenSSL and EVP. While it might be to much to go trough in one sitting, we advise you at least take a look at $ENGINE(3ssl)$, $EVP\_DigestInit(3ssl)$, $EVP\_SignInit(3ssl)$, and $EVP\_EncryptInit(3ssl)$.

After you have played around for a bit, you might want to read all of these more closely. For now, let's start typing some code.

Written by Jelte Jansen
© NLnet Labs, May 13, 2008