◾ File Security
The most fundamental scheme to protect user files is to give every user a login name and a password, allowing a user to use a system (see Chapter 2). To prevent others from accessing your files, keep the password for your computer account strictly confidential. The second scheme protects individual files by converting them to a form that is completely
different from the original version by means of encryption. This technique is used to protect your most important files, so that the contents of these files cannot be understood even if someone somehow gains access to them on the system. The third file protection scheme allows you to protect your files by associating access privileges with them, so that only a subset of users can access these files for a subset of file operations. In other words, the owner of the files can decide to whom to grant access to these files. All three mechanisms are described in this chapter, with emphasis on the third scheme.