ate which users may "modify, read or execute documents view folder contents, write to the file or folder, or have read-only access." In recent versions of Windows based on the NT kernel, you can see which user "owns" each file and folder within a given folder by using the Details view in Windows Explorer, right-clicking any tab at the top (e.g. Name, Size, Type, Date Modified), clicking "More," then "Owner."
The NTFS file system has built-in support for file and folder encryption through the EFS (Encrypted File System) tool. Right-click a file or folder, select "Properties," look under Advanced, and check Encrypt to use this feature. Once Encrypt is checked, click Details to identify the users who can decrypt the file. (Caution: Don't forget to disable System Restore before encrypting any file that System Restore can affect, or else another user with Recovery access can use System Restore to decrypt your encrypted file.)
Windows relies on "certificates" for public key security and for applications that provide for authentication, data integrity, and secure communications over networks. Users manage their own certificates.
The features listed above target email and file system encryption. You may also be interested in encryption for other applications, such as FTP and Telnet.
FTP (file transfer protocol) is inherently insecure because the program sends the user's log-in and password as plain text (i.e. unencrypted). You can encrypt the login and password, but the computer receiving the files must know how to decrypt them. Only a few FTP servers support secure connections, but there are some freeware programs available.
Telnet, a protocol used to access files on another computer, is similarly insecure because it sends the user's log-in and password as plain text. However, nearly anything you can do with Telnet can also be done with SSH (Secure Shell; look here for a FAQ). SSH was designed to be secure, but not all computers that support Telnet support SSH, since it's an entirely different protocol.
If you lock your door with a deadbolt instead of a chain, you make it more difficult for a burglar to get inside your home. Similarly, there are differences in the level of security that encryption software provides. Most of the well-known encryption algorithms that are considered "good" are mathematically complex enough to be difficult to break; otherwise, they wouldn't be so widely used. But even good algorithms are vulnerable to being broken if someone is persistent enough. In this section, we discuss the general vulnerabilities in encryption software, and offer tips that you can use to combat them. If you'd like more information on the vulnerabilities of a particular algorithm or software program, search the Web for reviews on its effectiveness.
General vulnerabilities include:
"Brute force" is another way of saying "trial and error." With this method, a "cracker" tries every possible key until he or she stumbles upon the correct one. No encryption software program it is entirely safe from the brute force method, but if the number of possible keys is high enough, it can make a program astronomically difficult to crack using brute force. For example, a 56-bit key has 256 possible keys. That's up to 72,057,594,037,927,936 seventy-two quadrillion keys that a cracker may have to try in order to find the correct one.
TIP: The more bits in a key, the more secure it is, so choose software with as many bits as possible. If you have a choice between 56-bit encryption and 128-bit encryption, for example, use the 128-bit encryption.
For more information on brute force cracking, please see Appendix A: "Brute Force" Cracking.
A "back door" is a security hole in a piece of software. A "back door" may be present because someone created it in the software with malicious intent, or by accident. Whatever the reason, if a malicious "cracker" discovers a "back door" in a program, he or she may be able to discover your key or password.
TIP: Make sure that the encryption software you choose has been rigorously tested. Read online reviews, and con