What information from the first node is used as the secret key during second node...

The security password is used as the secret key during the second node installation of Cisco Unified Contact Center Express (UCCX). This password is entered during the first node installation and must be the same for all nodes in the cluster. The security password is used to encrypt sensitive data in the database and to authenticate communication between nodes. If the security password is not the same for all nodes, the installation will fail and the cluster will not function properly. References: Cisco Unified Contact Center Express Install and Upgrade Guide, Release 12.5 (1) - Unified CCX Installation, Free Cisco Deploying Unified Contact Center Express (UCCXD) v6.0 Certification Sample Questions and Answers