This depends on what you want to use SNC for ? If you want to use SNC for ABAP server to ABAP server security, e.g. for RFC connections, then you can use the SAP crypto library supplied with SAP NetWeaver. There are instructions for this on SAP Help Library. If you want to use SNC for SAP GUI -> SAP ABAP authentication (e.g. SSO) then you would require an SNC library from a SAP partner company, if your SAP system is on UNIX or Linux. The vendor of such a product would then provide you with instructions for installation and setup. If you have any other requirement for SNC, please advise then we can guide you in the right direction.
As I mentioned in my last post, if you are using SAP GUI -> SAP ABAP with SNC, and SAP ABAP is on UNIX or Linux host, then you need to use a third-party product from a SAP partner. if you are using Active Directory for users to authenticate when they logon to Windows workstations, then it is common to use an SNC library that implements the Kerberos protocol so that benefits of SNC (encryption, data integrity etc.) can be given between SAP GUI on Workstations and SAP ABAP AS, and also SSO can be used if required to reduce the number of logons for the users.
Don't you also think that your subject title is a bit fluffy and that you could very easily have done some basic search for information before asking such a broad question?
The problem is that if everybody asks such questions before putting a bit of effort into a search in SAPHelp and the SMP, then we would be flooded with such basic questions and link-farms as answers.
We've been there, and we don't want to go back again..
Please read the forum rules and search in the [SAP EcoHub|http://ecohub.sdn.sap.com/] for certified providers of SNC solutions.