ith a basic overview of file transfer using FTP. Then some of the details on communication with FTP are discussed along with other methods for file sharing. The chapter concludes with implementation examples using the Perl programming language. File handling and transfer is an essential activity in an operation support solution. File Handling Additional Reading 1. Candace Leiden, Marshall Wilensky, and Scott Bradner. TCP/IP for Dummies. 5th ed. New York: For Dummies, 2003. 2. Pete Loshin. TCP/IP Clearly Explained. 4th ed. San Francisco, CA: Morgan Kaufmann, 2003. 3. Rod Scrimger, Paul LaSalle, Mridula Parihar, and Meeta Gupta. TCP/IP Bible. New York: John Wiley & Sons, 2001. 4. Laura A. Chappell and Ed Tittel. Guide to TCP/IP. Kentucky: Course Technology. 2001. Chapter 31 Secure Communication This chapter is about implement security in management applications. The different types of encryption and security protocols are discussed in this chapter. The chapter ends with an implementation example for encryption and decryption of messages. 31.1 Introduction The study of transforming messages in order to make them secure and immune to attacks is known as cryptography. The original text message without any trans- formation is said to be in plaintext format. After applying transformation on the original message to make it secure, the message is called ciphertext. The plaintext is transformed to the ciphertext by the user through the encryption algorithm and the ciphertext is transformed back to the plaintext by the receiver through the decryp- tion algorithm (see Figure 31.1). The process of ciphering (encrypting or decrypting) is performed using a key called the cipher, which is actually a number or a value. The key is kept secret and requires protection. In the encryption process the encryption key along with the encryption algorithm transforms the plaintext to the ciphertext and in the decryp- tion process the decryption key along with the decryption algorithm transforms the ciphertext to the plaintext (see Figure 31