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Encryption

All of the information, instructions, and recommendations on this Web site are offered on a strictly "as is" basis. Remember "Murphy's Law." Please take the proper precautions before attempting any of the tips or modifications listed here.

Contents

What is Encryption?

In cryptography, encryption is the process of transforming information (referred to as plaintext) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information (in cryptography, referred to as ciphertext). - Wikipedia.org

Encrypting File System (EFS)

The Encrypting File System (EFS) is a file system driver with filesystem-level encryption available in Microsoft's Windows 2000 and later operating systems. The technology transparently allows files to be encrypted on NTFS file systems to protect confidential data from attackers with physical access to the computer.

User authentication and access control lists can protect files from unauthorized access while the operating system is running, but are easily circumvented if an attacker gains physical access to the computer. One solution is to store the files encrypted on the disks of the computer. EFS does this using public key cryptography, and aims to ensure that decrypting the files is in theory impossible without the correct key. However, EFS is in practice susceptible to brute-force attacks against the user account passwords. In other words, encryption of files is only as strong as the password to unlock the decryption key. -Wikipedia.org

• Encrypting File System (EFS) (Wikipedia.org)
• EFS (Encrypting File System) (Webopedia.com)
• Protecting against EFS based attacks
  (Trojan utilizes Encrypting File System (EFS) to Protect Itself)
• Knowledge Base Articles on EFS

Beware of Windows encrypting file system (EFS) 'gotchas'

You might know that Windows has the ability to encypt files. This technology is part of Microsoft's Encrypting File System (EFS). Using EFS is a good way to protect data from being exposed to unauthorized people; however, there is a significant "gotcha" that you must take steps to guard against.

EFS encryption keys are generated on a per-installation and per-user basis. This means no two installations of XP will have the same keys. Therefore, if you reinstall XP, you could lose access to your encrypted data, because the keys will change upon reinstallation. One of our readers, Don Bissonnette, ran into this exact problem when he reinstalled Windows XP.

The way to make sure you don't lose access to your data after reinstalling XP is to make a backup of your private key before you reinstall XP. After you reinstall XP, simply restore your private key.

Microsoft has a few articles on its Web site that help you understand EFS and how to use it safely. For more information, refer to Knowledge Base article Q223316, "Best Practices for Encrypting File System," and the TechNet article "Data Protection and Recovery in Windows XP." - Windows Secrets Newsletter, Issue 122, 2007-09-13