Although encryption is a technology that will be widespread in the future, it is already hard at work on the World Wide Web today. In recent years, more than a dozen cryptographic systems have been developed and fielded on the Internet.
Working cryptographic systems can be divided into two categories. The first group are programs and protocols that are used for encryption of email messages. These programs take a plaintext message, encrypt it, and either store the ciphertext or transmit it to another user on the Internet. Such programs can also be used to encrypt files that are stored on computers to give these files added protection. Some popular systems that fall into this category include the following:
The second category of cryptographic systems are network protocols used for providing confidentiality, authentication, integrity, and nonrepudiation in a networked environment. Such systems require real-time interplay between a client and a server to work properly. Some popular systems that fall into this category include the following:
All of these systems are summarized in Table 11.1 and are described in the sections that follow. For detailed instructions on using these systems, please refer to the references listed in the Appendixes.
One of the first widespread public key encryption programs was Pretty Good Privacy (PGP), written by ...