Before we talk about information security, let us define information. In general, information is an asset with intrinsic value to the owner. Because it has this intrinsic value, there is need to protect it. However, for people in technology, information means a collection of processed data (data are strings of 0s and 1s). These strings of 0s and 1s have meaning and, therefore, intrinsic value. In either case, information is an asset with value to the owner and it must
be protected. The security of information, therefore, means the protection of these asserts of value. Alternatively, we can define information security as mechanisms to safeguard information.
The CIA Security Model
The three basic elements of security (confidentiality, integrity, and availability) are at the core of the information security architecture. It is upon these that other security elements are built as shown in Figure 1.
Confidentiality
Confidentiality of information means that there has been no unauthorized disclosure of that information. It further insures that information is private and that there is transparency. In data communication, confidentiality is a state or a situation where there is no fear that messages being sent or received are not being intercepted and read by a third party, known as an eavesdrop- per. This can happen if the message either is transmitted in the clear or the encryption used on the message before it is sent is weak and can easily be broken. In both symmetric and asymmetric encryption, the use of a short key can result in an intruder interception. In both cases, ways must be found to make the key hard to break. In symmetric encryption, one way is to use a strong key of 100 bits or longer (see standard encryption algorithms like
Figure 1. The CIA information security model
Integrity
Confidentiality
Availability
DES, 3DES, AES, IDEA, RC4, and PGP) and also to use a key authority at a key distribution center (KDC), which prevents the passing of private keys. It is also the case in asymmetric encryption to use a longer key for strength of the encryption (see standard encryption algorithms like RSA and ECC) and a good public key exchange
Integrity
Data integrity is ensuring that a stream of messages, a single message, or a
selected field within a message sent or received has had no duplication, inser-
tion or modification, reordering, destruction, or replays, and there have been
no processes or processes that have caused corruption of the data. Methods to ensure data integrity must be able to detect the violations. And these methods include encryption, authentication, authorization, and nonrepudiation.
Encryption
This is a technique to protect communications channel from sniffers and programs written purposely for and installed on the communication channels
to eavesdrop on network traffic examining all traffic on selected network seg-
ments. Sniffers are easy to write and install, but difficult to detect. Encryption
requires an encryption algorithm and a key to transform data at the source, called plaintext, into an encrypted form, called ciphertext, which is usually
unintelligible, and finally to recover it at the destination. The encryption
algorithm can either be symmetric or asymmetric.
Symmetric.encryption or secret key encryption, as it is usually called, uses a common key and a cryptographic algorithm to scramble and unscramble the message. The security of the transmitted information depends on the fact that eavesdroppers with no knowledge of the key are unable to read the message. One problem with symmetric encryption is the security of the key that must be passed from the sender to the receiver.
To overcome this problem, a different type of encryption called asymmetric. encryption is used. In asymmetric encryption, commonly known as public key encryption, two different keys are used: a public key know by all and a private key known only by the sender and the receiver. Both the sender and the receiver have a pair of these keys, one public and one private. To encrypt a message from sender to receiver, both the sender and the receiver must create their own pairs of keys. Then they exchange their public keys, which anybody can get from public directories. When the sender is to send
a message M to the receiver, the sender must use the receiver’s public key to encrypt M. On receipt of M, the receiver must then use his or her private key to decrypt the message M.
Authentication
You have probably by now heard of the famous New Yorker cartoon with the caption: “On the Internet, no one knows you’re a dog.” It says a million words about authentication in modern times and the need for it. Usually it is
difficult for a system to verify the identity of a user, especially a remote user.
Thus authentication is a process whereby the system gathers and builds up information about the user and uses this information to associate that user’s identity with a stored token, which could be a statement, an action, or an event, to assure that the user is genuine. Most importantly, in data communication, to allow the computer to distinguish between legitimate users and others users with dubious motives, authorized users must be able to identify themselves to the authenticating agent. As we will see in the coming chapters, there are three authenticating pillars that give us the identity of the user (Bishop, 2004):
1. Something.you.know, like a password, a phrase, personal identifica-
tion numbers (PINs), and secret handshake. The password is the most
widely used identification element. Because of this, there must be a
strong password policy. Problems with passwords are that they can be stolen or forgotten.
2. Something. you. have, like a token. There are two types of tokens: storage and dynamic tokens. Storage tokens consist of smart cards and universal serial bus (USB). Dynamic tokens, on the other hand, come in many forms, including smart cards and USB. However, unlike storage tokens, dynamic tokens are used to create a one-time use token, which makes them more secure. The problem with all types of tokens is that whoever has it is the legitimate user.
3. Something.you.are, like a biometric trait. Physical traits can be relied on more for authentication, than the previous two pillars of authentica- tion. Biometrics are a new form of authentication that is believed to be more secure than the other two. Biometrics are believed to be safer than passwords and tokens because one cannot forget his or her biological
By using encryption, we can ensure authentication of the user with either symmetric or asymmetric encryption. In symmetric encryption, authentica- tion is assured, though not very strongly, by assuming that if no third party has access to the secret key, then the receiver of the message can be assured that the message indeed must have come from the sender, because it is only the sender who has the secret key. In asymmetric encryption, authentication is more assured if the sender encrypts the message using his or her private key. The receiver then uses his or her public key to decrypt the message. Authentication is assured because the sender is the only one with the private key. Authentication also can be assured through generation of an authentica- tion code or digital signature, which is appended at the end of the message before transmission. We will talk more about digital signatures shortly.
Nonrepudiation
In a nondigital world, courts recognize signatures so that the signer cannot turn around and disown a document he or she signed. In the digital world, the same process is also in place to prevent either a sender or receiver from denying a transmitted message. However, a digital signature is used. Once the message has been sent, the receiver can prove that it was sent by a given sender.
A digital.signature is similar to handwritten signatures in printed documents. Just like handwritten signatures, digital signatures ensure that the person whose signature the system is authenticating is indeed the true person, but digital signatures provide a greater degree of security than handwritten sig- natures.
A digital signature is actually a code generated by a mathematical algorithm, like the hash function, which is attached to the message, and then the combo is encrypted before it is sent to the recipient. Sometimes, with digital signature attached, the message is sent in the clear—just like sending a postcard
Availability
Availability of information means that a person authorized to access informa- tion can get access to it at any time such access is needed. That means that information and the services to access it are accessible by the authorized user. It also means that there is enough capacity provided to the user to meet the
service needs of that user. Finally, the system must also remain accessible during the servicing of the request.
There are various techniques for which these three elements can be used to
enhance information security. However, it has become increasing difficult to
cover all information security concerns with only these three. This has lead to a hunt for additional tools. We will look at these tools in the last chapter.