950 words - 4 pages

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 ...view middle of the document...

This relationship ties the keys in the pair exclusively to one another: a public key and its corresponding private key are paired together and are related to no other keys.

This pairing is possible because of a special mathematical relationship between the algorithms for the public keys and private keys. The key pairs are mathematically related to one another such that using the key pair together achieves the same result as using a symmetrical key twice. The keys must be used together; each individual key cannot be used to undo its own operation. This means that the operation of each individual key is a one-way operation; a key cannot be used to reverse its operation. In addition, the algorithms used by both keys are designed so that a key cannot be used to determine the opposite key in the pair. Thus, the private key cannot be determined from the public key. The mathematics that makes key pairs possible, however, contributes to one disadvantage of key pairs as opposed to symmetric keys. The algorithms used must be strong enough to make it impossible for people to use the known public key to decrypt information that has been encrypted with it through brute force. A public key uses mathematical complexity and its one-way nature to compensate for the fact that it is publicly known to help prevent people from successfully breaking information encoded with it.

Applying this concept to the preceding example, the sender would use the public key to encrypt the plaintext into ciphertext. The recipient would then use the private key to decrypt the ciphertext back into plaintext.

Because of the special relationship between the private key and public key in the key pair, it is possible for one person to use the same key pair with many people rather than having to use a different key with each individual person. As long as the...

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