Public-Key Cryptography

Information Security overview for Managers and policy Makers

ITM517 Module 5 Case Study

Public-key cryptography

March 6th, 2013

Introduction

Cryptography is the study of protecting information through the use of codes and ciphers. Cryptography forms a fundamental part of message security. At its simplest form, is a process of methodically changing information to make it unreadable without knowing how that information was changed. One of the earliest and simplest codes (called a Caesar cipher) worked by taking the alphabet and shifting all the letters by a fixed number. The sender and recipient would both know how many letters to shift and thus could use this code to change information so that each would be able to understand, but no one else could understand. This process of changing information into a code is encryption and the process of changing code back is decryption. The original message is referred to as "plaintext." The changed message is referred to as "ciphertext." The information that is used to change the plain text into ciphertext is referred to as the key. The particular way in which a key changes information is referred to as the algorithm.

How public Key Cryptography works

(Galbrith 2012) In 1976, Whitfield Diffe and Martin Hellman created public key cryptography. Public key cryptography represents a major innovation because it fundamentally alters the process of encryption and decryption. Instead of a single shared, secret key, Diffe and Hellman proposed the use of two keys. One key, called the "private key" remains a secret. Instead of being shared between parties, it is held by only one party. The second key, called the "public key," is not a secret and can be shared widely. These two keys or "key pair" as they are called, is used together in encryption and decryption operations. The key pair has a special, reciprocal relationship so that each key can only be used in conjunction with the other key in the pair. This relationship...