OpenSSL:
http://www.openssl.org/
+RPMs of OpenSSL are available in the support/ directory of the OpenSSH
+mirror site. OpenSSH requires OpenSSL version 0.9.5 or later.
+
OpenSSH can utilise Pluggable Authentication Modules (PAM) if your system
supports it. PAM is standard on Redhat and Debian Linux and on Solaris.