# 数学代写|密码学作业代写Cryptography代考|Basic Information Theory

#### Doug I. Jones

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• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础
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## 数学代写|密码学作业代写Cryptography代考|The Information Age

It is often stated that we live in an information age. This would clearly make information theory pertinent not only to an understanding of cryptography but also to an understanding of modern society. First, we must be clear on what is meant by the phrase “information age.” To a great extent, the information age and the digital age go hand in hand. Some might argue the degree of overlap; however, it is definitely the case that without modern computers, the information age would be significantly stifled. While information theory began before the advent of modern digital computers, the two topics are still inextricably intertwined.

From one perspective the information age is marked by information itself becoming a primary commodity. Clearly, information has always been of value. But it was historically just a means to a more concrete end. For example, even pre-historic people needed information, such as where to locate elk or other games. However, that information was just peripheral to the tangible commodity of food. In our example, the food was the goal; that was the actual commodity. The information age is marked by information itself being widely considered a commodity.

If you reflect on this just briefly, I think you will concur that in modern times information itself is often viewed as a product. For example, you purchased this book you now hold in your hands. Certainly, the paper and ink used to make this book were not worth the price paid. It is the information encoded on the pages that you paid for. In fact, you may have an electronic copy and not actually have purchased any pages and ink at all. If you are reading this book as part of a class, then you paid tuition for the class. The commodity you purchased was the information transmitted to you by the professor or instructor (and of course augmented by the information in this book!) So clearly information as a commodity can exist separately from computer technology. The efficient and effective transmission and storage of information, however, require computer technology.

Yet another perspective on the information age is the proliferation of information. Just a few decades ago, news meant a daily paper, or perhaps a 30 -minute evening news broadcast. Now news is 24 hours a day on several cable channels and on various internet sites. In my own childhood, research meant going to the local library and consulting a limited number of books that were, hopefully, not more than 10 years out of date. Now, at the click of a mouse button, you have access to scholarly journals, research websites, almanacs, dictionaries, encyclopedias, and avalanche of information. Thus, one could view the information age as the age in which most people have ready access to a wide range of information.

Younger readers who have grown up with the internet, cell phones, and generally being immersed in a sea of instant information may not fully comprehend how much information has exploded. It is important to understand the explosion of information in order to fully appreciate the need for information theory. To provide you some perspective on just how much information is being transmitted and consumed in our modern civilization, consider the following facts. As early as 2003 , experts estimated that humanity had accumulated a little over 12 exabytes of data over the entire course of human history. Modern media such as magnetic storage, print, and film had produced 5 exabytes in just the first 2 years of the twenty-first century. In 2009 , researchers claimed that in a single year, Americans consumed over 3 zettabytes of information. As of 2019 the World Wide Web is said to have had 4.7 zettabytes, or 4700 exabytes of data. That is just the internet, not including offline storage, internal network servers, and similar data. If you were to try to put all that data on standard external drives, such as 4 terabyte external drives that are quite common as of this writing, it would take $109,253,230,592$ such drives.

## 数学代写|密码学作业代写Cryptography代考|Claude Shannon

It is impossible to seriously examine information theory without discussing Claude Shannon. Claude Shannon is often called the father of information theory (Gray 2011). He was a mathematician and engineer who lived from April 30, 1916 until February 24,2001 . He did a great deal of fundamental work on electrical applications of mathematics and work on cryptanalysis. His research interests included using Boolean algebra (we will discuss various algebras at length in Chap. 5) and binary math (which we will introduce you to later in this chapter) in conjunction with electrical relays. This use of electrical switches working with binary numbers and Boolean algebra is the basis of digital computers.

During World War II, Shannon worked for Bell Labs on defense applications. Part of his work involved cryptography and cryptanalysis. It should be no surprise that his most famous work, information theory, has been applied to modern developments in cryptography. It should be noted that in 1943, Shannon became acquainted with Alan Turing, whom we discussed in Chap. 2. Turing was in the United States to work with the US Navy’s cryptanalysis efforts, sharing with the United States some of the methods that the British had developed.

Information theory was introduced by Claude Shannon in 1948 with the publication of his article A Mathematical Theory of Communication (Guizzo 2003). Shannon was interested in information, specifically in relation to signal processing operations. Information theory now encompasses the entire field of quantifying, storing, transmitting, and securing information. Shannon’s landmark paper was eventually expanded into a book. The book was entitled The Mathematical Theory of Communication and was co-authored with Warren Weaver and published in 1963.
In his original paper, Shannon laid out some basic concepts that might seem very elementary today, particularly for those readers with an engineering or mathematics background. At the time, however, no one had ever attempted to quantify information nor the process of communicating information. The relevant concepts he outlined are given below with a brief explanation of their significance to cryptography:

• An information source that produces a message. This is perhaps the most elementary concept Shannon developed. There must be some source that produces a given message. In reference to cryptography, that source takes plain text and applies some cipher to create cipher text.
• A transmitter that operates on the message to create a signal which can be sent through a channel. A great deal of Shannon’s work was about the transmitter and channel. These are essentially the mechanisms that send a message, in our case an encrypted message, to its destination.
• A channel, which is the medium over which the signal, carrying the information that composes the message, is sent. Modern cryptographic communications often take place over the internet. However, encrypted radio and voice transmissions are often used. In Chap. 2 you were introduced to IFF (Identification Friend or Foe) systems.
• A receiver, which transforms the signal back into the message intended for delivery. For our purposes the receiver will also decrypt the message, producing plain text from the cipher text that is received.
• A destination, which can be a person or a machine, for whom or which the message is intended. This is relatively straightforward. As you might suspect, sometimes the receiver and destination are one and the same.

# 密码学代写

## 数学代写|密码学作业代写Cryptography代考|Claude Shannon

• 产生消息的信息源。这也许是香农提出的最基本的概念。必须有一些来源产生给定的消息。关于密码学，该来源采用纯文本并应用一些密码来创建密文。
• 对消息进行操作以创建可以通过通道发送的信号的发送器。香农的大量工作都是关于发射器和信道的。这些本质上是将消息（在我们的例子中是加密消息）发送到目的地的机制。
• 信道，即承载构成消息的信息的信号通过其发送的媒介。现代密码通信通常通过互联网进行。但是，通常使用加密的无线电和语音传输。在第一章 2 向您介绍了 IFF（敌我识别）系统。
• 接收器，它将信号转换回要传递的消息。出于我们的目的，接收方还将解密消息，从接收到的密文生成明文。
• 目的地，可以是人或机器，消息是为谁或谁准备的。这是相对简单的。您可能会怀疑，有时接收者和目的地是同一个。

## 有限元方法代写

tatistics-lab作为专业的留学生服务机构，多年来已为美国、英国、加拿大、澳洲等留学热门地的学生提供专业的学术服务，包括但不限于Essay代写，Assignment代写，Dissertation代写，Report代写，小组作业代写，Proposal代写，Paper代写，Presentation代写，计算机作业代写，论文修改和润色，网课代做，exam代考等等。写作范围涵盖高中，本科，研究生等海外留学全阶段，辐射金融，经济学，会计学，审计学，管理学等全球99%专业科目。写作团队既有专业英语母语作者，也有海外名校硕博留学生，每位写作老师都拥有过硬的语言能力，专业的学科背景和学术写作经验。我们承诺100%原创，100%专业，100%准时，100%满意。

## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。

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