Fundamentals of Information Encryption - Multilevel Security for Relational Databases - page 66

Confidentiality protects the information from unauthorized
access. An unauthorized party is called an adversary, which
should not have the ability to access the network.
Data integrity ensures that the information has not been modi-
fied in an unauthorized way. If the data are modified, all par-
ties through the network can detect this modification.
Authentication methods are classified into two categories: entity
authentication and message authentication. Entity authenti-
cation is the process that one party uses to ensure the identity
of the second party in the communication protocol. Message
authentication is the term used with data origin authentica-
tion. It provides that the data received is the original message
source.
Nonrepudiation means that the receiver can prove that he
receives the original information as the sender sends it.

Knowing the techniques that are used to break an existing cryp-
tography is called cryptanalysis. Because the cryptography depends
on the cryptanalysis, users refer to cryptology as a joint study of
cryptography and cryptanalysis.

4.2.2 Principles of Encryption

The basic idea of encryption is to modify the message in such a way that
only a legal recipient can reconstruct its content [37,38]. A discrete-valued
cryptosystem can be characterized by:

• A set of possible plaintexts, P
• A set of possible ciphertexts, C
• A set of possible cipher keys, K
• A set of possible encryption and decryption transformations,
E and D

An encryption system is also called a cipher, or a cryptosystem.
The message for encryption is called plaintext, and the encrypted
message is called ciphertext . Denote the plaintext and the ciphertext
by P and C, respectively. The encryption procedure of a cipher can
be described as

()

CE P (4.1) K e