Secure Store Service -SharePoint 2010

SSS: Secure Store Service in SharePoint 2010 replaces the single Sign On feature available in SharePoint 2007. It is a shared service that provides storage and mapping of credentials. It helps to correct the external systems through secure store data, it is specific to individual or group. SSS can be used to store and map the user credentials required by external system.

Following services can use SSS in SharePoint 2010:
Excel Services  
Visio Services  
PerformancePoint Services  
PowerPivot for SharePoint 2010   
Microsoft Business Connectivity Services

It is recommended to run the SSS in a separate application pool that is not used for any other service, Run the Secure Store Service on a separate application server that is not used for any other service.
 Before generating a new encryption key, back up the Secure Store database

Secure store service and claims authentication

Steps to create SSS:
Create a Service account and provide DBO permission at DB server.
CA --> Manage Service application -->   New -->Enter Service application name --> Enter DB server and DB name --> Enter or select the application pool name --> Select the service account for this SSS through managed account.

Once the SSS is created enter the Target ID --> Set credential and Permission