Here is a handle little PS module I picked up from halr9000.com to import/export credentials to a file securely. The only person who can import and therefore decrypt the file is the user who exported it.
$creds = Get-Credential
Export-PSCredential -Credential $creds -Path 'c:\temp\creds.xml'
$newCreds = Import-PScredential -Path 'C:\Temp\creds.xml'