60 Chapter 3 ■ Cryptography
■ Secure Hash Algorithm (SHA)
■ Secure Sockets Layer (SSL)
■ Pretty Good Privacy (PGP)
■ Secure Shell (SSH)RSA is a public-key cryptosystem for both encryption and authentication
that was invented by Ron Rivest, Adi Shamir, and Leonard Adleman. The
RSA algorithm is built into current operating systems by Microsoft, Apple,
Sun, and Novell. In hardware, the RSA algorithm can be found in secure
telephones, on Ethernet network cards, and on smart cards. RSA is also
well known by the company that bears the name, RSA.In many cases, encryption technologies are not only an important part of a technology
or system but a required part that cannot be excluded. For example, e-commerce and simi-
lar systems responsible for performing financial transactions cannot exclude encryption for
legal reasons. Introducing encryption to a system does not ensure bulletproof security as it
may still be compromised—but encryption does make hackers work a little harder.So How Does It Work?
Cryptography has many different ways of functioning. Before you can understand the basic
process, you must first become familiar with some terminology. With this in mind, let’s
look at a few of the main terms used in the field of cryptography.Plaintext/Cleartext Plaintext is the original message. It has not been altered; it is the
usable information. Remember that even though Caesar’s cipher operates on text, it is but
one form of plaintext. Plaintext can literally be anything.Ciphertext Ciphertext is the opposite of plaintext; it is a message or other data that has
been transformed into a different format using a mechanism known as an algorithm. It is
also something that can be reversed using an algorithm and a key.Algorithms Ciphers, the algorithms for transforming cleartext into ciphertext, are the
trickiest and most mysterious part of the encryption process. This component sounds
complex, but the algorithm or cipher is nothing more than a formula that includes discrete
steps that describe how the encryption and decryption process is to be performed in a given
instance.Keys Keys are an important, and frequently complicated, item. A key is a discrete piece of
information that is used to determine the result or output of a given cryptographic opera-
tion. A key in the cryptographic sense can be thought of in the same way a key in the physi-
cal world is: as a special item used to open or unlock something—in this case, a piece of
information. In the encryption world, the key is used to produce a meaningful result and
without it a result would not be possible.