Porter Model

Abstract

In cryptography, encryption is the process of transforming information (referred to as plaintext) using an algorithm (called a cipher) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information (in cryptography, referred to as cipher text). The reverse process, i.e., to make the encrypted information readable again, is referred to as decryption (i.e., to make it unencrypted)

In many contexts, the word encryption may also implicitly refer to the reverse process, decryption e.g. “software for encryption” can typically also perform decryption.

By definition, an encryption system (herein referred to as a cryptosystem) is the combination of three elements: an encryption engine, keying information, and operational procedures for its secure use. In general, a cryptosystem refers to a suite of algorithms needed to implement a particular form of encryption and decryption technique. A cryptosystem consists of three algorithms: one for key generation, one for encryption, and one for decryption. Their application to industrial control systems may present design and operational challenges.

Introduction

Encryption is the conversion of data into a form, called a ciphertext, that cannot be easily understood by unauthorized people. Decryption is the process of converting encrypted data back into its original form, so it can be understood.

The use of encryption/decryption is as old as the art of communication. In wartime, a cipher, often incorrectly called a code, can be employed to keep the enemy from obtaining the contents of transmissions. (Technically, a code is a means of representing a signal without the intent of keeping it secret; examples are Morse code and ASCII.) Simple ciphers include the substitution of letters for numbers, the rotation of letters in the alphabet, and the "scrambling" of voice signals by inverting the sideband frequencies. More complex...