Types of File Encryption in Server 2003

Posted: May 23, 2010 in Security, Server, Server 2003, System Information
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If you have evaluated EFS in Windows 2000 and found critical features missing, it’s worth taking a second look at EFS in Windows Server 2003 and XP. The changes include the following:

  • New and more cryptographically robust encryption methods. You can now choose between DESX encryption (used by Windows 2000) and 3DES (Triple-DES), an algorithm that complies with government standards for handling of non-classified documents.
  • Offline file encryption. This feature is one of the most significant improvements in Windows Server 2003 and XP. It enables users to use a highly convenient feature, offline file storage, while retaining the ability to protect their files with encryption.
  • Encrypted file transfer over WebDAV. The Web-based Distributed Authorizing and Versioning redirector uses HTTP rather than SMB. Encrypted files are transferred in their encrypted state rather than being decrypted prior to transport as happens with SMB. Also, servers can store encrypted files using WebDAV without compromising security with Kerberos delegations.
  • More flexible group policy control. EFS can now be disabled throughout a domain with a single click of the mouse in a group policy. This contrasts with Windows 2000, which requires removing and re-importing X.509 certificates to control encryption.
  • Shared encrypted files. Users with encrypted files can assign access to other users. This enhances the use of EFS in a workgroup. Only individual users can be given access, not groups. Additional users can only be selected by users who already have access.
  • Copy warnings. Explorer now warns users when they attempt to copy or move encrypted files to an unprotected location such as a Zip drive, floppy drive, or FAT partition. New switches in COPY and XCOPY permit overriding these protections, if necessary.
  • Visual cues. The Explorer shell now shows the names of encrypted files and folders in a different color, similar to the way compressed files are displayed in Windows 2000.
  • Improved command-line administration. The CIPHER command-line utility has been updated with several new features, including the ability to generate file recovery certificates, the ability to search for encrypted files on a volume, the ability to refresh certificates for all encrypted files on a volume, and the ability to wipe all unused disk space to remove temporary files. (The wipe feature was released in Windows 2000 SP3.)
  • Security improvements. Although not strictly an EFS improvement, the handling of the crypto Master key has been changed so that it is not updated when a local user password is changed by anyone other than the user. This eliminates a serious deficiency for standalone laptops and desktops. Now a hacker cannot use utilities to change a user’s password (or the Administrator password) on a standalone machine to gain access to encrypted files.

Not every change is a welcome one, however. In Windows 2000, files cannot be encrypted without the certificate of a Data Recovery Agent (DRA). This ensures that a user cannot encrypt files and then quit the company and leave you without a means of recovering the files. In Windows Server 2003 and XP, it is possible to encrypt files without a DRA. This “feature” has potentially serious consequences because users could encrypt their files and then lose the private key, thereby losing access to the files permanently.

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