#The command to encrypt xfile is how to

Providing the key on the command line is almost always a bad idea (you’ll see why later in this chapter).

In particular, we will discuss the popular Pretty Good Privacy system.) The type of encryption used by the crypt command is called private key encryption, since anyone who knows the encryption key can easily find the decryption key In fact, for crypt the encryption key and the decryption key are exactly the same! (Later in this chapter we will discuss a different kind of encryption system, known as a public key system, where knowing the encryption key does not provide useful help for decryption. Do not forget the key you use to encrypt a file, because if you do, you cannot recover the file-not even the system administrator will be able to help. To use crypt to encrypt a file, you need to supply an encryption key, either as an argument on the command line, as the response to a prompt, or as an environment variable. We will also describe replacements for it that can be used for serious encryption.

#The command to encrypt xfile is how to

After we discuss how to use crypt, we will explain why files encrypted using it are vulnerable to attack and why it is not included in Linux. Note that the crypt command, if available on your system, cannot withstand serious attack. We will describe how to use the crypt command here. Many UNIX variants, other than Linux distributions, provide the crypt command for file encryption. The original contents of the file are known as plaintext or cleartext. However, by decrypting the file, you can recover its original contents. When you encrypt the contents of a file, you use a procedure that changes the contents of the file into seemingly meaningless data, known as ciphertext. You can protect the confidentiality of files by encrypting their contents. Or you may have source code for some application program that you want to keep secret.

For instance, you may have some confidential personnel records that you do not want others to read. You may want to keep some of your files confidential, so that no other user can read them, including the superuser.