OpenSSL

Here is a worksheet/guide to the OpenSSL command tool: Here

Here are some useful links:

Address Description
http://www.opensslbook.com/code.html Source code examples from the excellent - Network Security with OpenSSL
http://www-106.ibm.com/developerworks/linux/library/l-openssl.html A nice introductory article from the IBM developer works series. (Has sample code)
http://www.pseudonym.org/ssl/ssl_cook.html Rather a lot here! - No code.
http://tirian.magd.ox.ac.uk/~nick/openssl-certs/ca.shtml Lots about certificates and certificate authorities.
http://www.rtfm.com/openssl-examples/ The code from the SSL tutorial PDFs (Remember ./configure then make)
http://slacksite.com/apache/certificate.html More on certificates.
http://docs.hp.com/en/T1428-90052/ch07s03.html Covers how to secure HPs AAA server but uses OpenSSL.
http://wp.netscape.com/eng/security/SSL_2.html SSL 2.0 Specification
http://wp.netscape.com/eng/ssl3/index.html SSL 3.0 Specification
http://www.flatmtn.com/computer/Linux-SSLCertificates.html Certificates
http://sapiens.wustl.edu/~sysmain/info/openssl/openssl_ca.html Creating a certificate authority

There are many excellent books on the subject of SSL\TLS but for me the best has to be Network Security with OpenSSL.

C Hints and tips:

sprintf - http://www.rohitab.com/discuss/static/topic-3-18-11505-0.html