SharePoint 2010 - FIM Key

FIM Synchronization Service encryption key

In the case the of DR or a complete rebuild of a SharePoint 2010 environment it is very important that you back the up the FIM key on initial install of the environment. Without this on a rebuild you will NOT be able to re- start the user profile service.

To export the key:

1. From command prompt go to Program Files%\Microsoft Office Servers\14.0\Synchronization Service\Bin
2. Type miiskmu.exe /e D:\<path>\FIM_Key
3. This will backup the key to a directory - then and this is also important copy this off to another location just in case of OS failure.
4. the user name and password are the credentials for the farm administrator.
    

1. To import the encryption key, say on rebuild - complete these steps:
   
2. Use farm admin to log on to the computer that contains the new User Profile Service service application database.
   
3. Ensure the  User Profile Synchronization service has a status of the service is Stopped.
   
4. Open the Command Prompt window, and then change to the following folder:
   
   %Program Files%\Microsoft Office Servers\14.0\Synchronization Service\Bin\
   
5. Type the following command, and then press Enter:
   
   miiskmu.exe /i  D:\<path>\FIM_Key
   
   Where <Path> is the full path of the file to which you exported the key.

The following like is slightly less clear - 
http://technet.microsoft.com/en-us/library/ff806338.aspx