Advanced security data is stored in the Kmsdata subdirectory where you installed the Microsoft Exchange Server. You can back up the advanced security data using the Windows NT Backup utility to back up all files and subdirectories in this directory. Stop the Microsoft Key Management Server service before performing the backup.
Caution You should periodically back up the Key Management archive database. If a user's security file is corrupted or a security logon password is forgotten, encrypted messages, including all previously encrypted messages, cannot be opened by the user. The key must be recovered as described in "Recovering Advanced Security Keys" earlier in this chapter, and the advanced security data must be current for this operation to succeed.
For more information, see your Windows NT documentation or Microsoft Exchange Server Maintenance and Troubleshooting.