There are many ways to encrypt a network drive. Encrypting a network share on the Windows system is possible by using various methods known as NTFS encryption, which provide access to an encrypted file or entire drive below the user’s login credentials. Another option that will allow others to decrypt files with their specific username and password can be created with BitLocker To Go, which facilitates data protection in offline environments for removable devices such as USB keys or external hard drives. If both your server and client system are running Mac OS X Lion there is Apple Filevault 2, which encrypts the content of System Folders and any local disks including Time Machine disks without interrupting users' activities when they log in.