本文是留学生计算机作业代写范例，题目是“Analysis of the Role of Cryptography in Network Security（密码学在网络安全中的作用分析）”，网络安全涉及到保护网络资源不被篡改、破坏和未经授权的使用，密码学和加密技术是网络安全中最重要的组成部分。在我的作业中，作为一名网络安全管理者，我将尝试研究“探索各种密码方案的性能，评估web安全和无线网络系统的安全性”。在我的研究中，作为一个网络安全管理者，我将分析密码学，网络安全和无线网络系统的安全，以实现组织未来的网络安全策略。
Abstract 摘要
Network security is concerned with the protection of network resources against alteration, destruction and unauthorized use, cryptography and encryption are most critical components of network security. In my assignment, as a network security manager, I will try to research “explore the performance of various cryptographic schemes and evaluate web security and the security of wireless network system”.In my research, as a network security manager, I will analyze cryptography, web security, and security of wireless network system to implement the network security strategies for the organisation in future.
Networks take all kind of sensitive data and security play a vital role of any wireless network system. Security certify level of data integrity and data confidentiality as maintain wired network, without accurately implement security measures and wireless network adapter come within range of the network adapter. Security is high lack, laziness, and lack of knowledge and employee are not aware of these things, especially in small organisation and home, every organisation need to aware and training for employees time to time. Cryptology has two components, kryptos and logos. Cryptographic methods to certify the safety and security of communication and main goal is user authentication, data authentication such as integrity and authentication, non-repudiation of origin, and confidentiality and it has two functions encryption and decryption.
网络承载着各种敏感数据，而安全对于任何无线网络系统都起着至关重要的作用。安全认证的数据完整性和数据保密性等级维护有线网络，没有准确实施安全措施和无线网卡在网卡范围内。安全性高缺乏，懒惰，缺乏知识和员工不知道这些事情，特别是在小型组织和家庭，每个组织都需要意识到和培训员工的时间。密码学有两个组成部分，kryptos和logos。认证通信安全的密码方法主要目标是用户认证、数据认证如完整性和认证、来源不可否认性和保密性，它具有加解密两种功能。
1.Explore and explain different types of cryptography and assess the role of cryptography in network security.探索和解释不同类型的密码学，并评估密码学在网络安全中的作用。
Cryptography has different methods for taking clear, readable data, and converts into unreadable data of secure communication and also transforms it back. Cryptography is also used to authenticate identify of message source and certify integrity of it. Cipher send message and use secret code. “The cipher scrambles the message so that it cannot be understood by anyone other than the sender and receiver. Only the receiver who has the secret code can decipher the original message, thus ensuring confidentiality.” (Citrix-system, 2010)
密码学有不同的方法来获取清晰的、可读的数据，并将其转换为安全通信中的不可读数据，也将其转换回来。密码学还用于验证消息源的身份和验证消息源的完整性。密码发送消息并使用密码。密码将信息打乱，除了发送者和接收者，其他人无法理解。只有拥有密码的接收者才能破译原始信息，从而保证了信息的机密性。”(Citrix-system, 2010)
2.Type of cryptography类型的加密
Following three common types of cryptography as below: Secret key cryptography is identified as symmetric key cryptography. Both sender and receiver know same secret code described the key and messages are encrypted by the sender and use key, decrypted by the receiver. It use single key for both encryption and decryption. This method works healthy “if you are communicating with only a limited number of people, but it becomes impractical to exchange secret keys with large numbers of people”. Secret key cryptography use is such as data encryption standard, advance encryption standard, Cast-128/256, international data encryption algorithm, and rivest ciphers etc. (Citrix-system, 2010)
以下三种常见的密码学类型如下:密匙密码术被标识为对称密匙密码术。发送方和接收方都知道描述密钥的相同密码，消息由发送方加密，使用密钥，由接收方解密。它使用单密钥进行加密和解密。“如果您只与有限数量的人通信，但与大量的人交换密钥就变得不切实际”，这种方法运行良好。秘钥加密使用的是如数据加密标准、先进加密标准、Cast-128/256、国际数据加密算法、rivest密码等(Citrix-system, 2010)。
Public key cryptography is called asymmetric encryption and use couple of keys one for encryption and another for decryption. Key work in pairs of coordination public and private keys. Public key can freely distributed the private key. If senders and receivers don’t have to communicate keys openly, they can give private key to communication confidentially. Public key cryptography use for key exchange and digital signatures such as RSA, digital signature algorithm, public-key cryptography standard etc.
Hash functions use a mathematical transformation to permanently encrypt information. It also called message digests and one way encryption. Hash function use to provide a digital fingerprint of file contents and it is commonly employed by many operating system to encrypt passwords and it provide measure of the integrity of a file. It is also use message digest, secure hash algorithm, RIPEMD etc. (Kessler, G,2010)
3.The role of cryptography密码学的作用
Many feature combine to throw network security to the top issues in the organisation and face IS professional daily. Nowadays business operation decentralization and correspondence growth of computer network is the number one driver of concern about the network security. As far as security concern, many organisation networks are accidently waiting to occur, such accident will occur is impossible to predict but security breaches will occur. When organisation network security chooses is 100% involve cryptography technology. The following five basic uses of cryptography in network security solution are:
许多特点结合起来，把网络安全扔到组织的首要问题和面对IS专业的日常。目前，企业运营的分散化和计算机网络的通信增长是人们关注网络安全的首要因素。就安全而言，许多组织网络都在等待意外的发生，这种意外的发生是不可能预测的，但安全漏洞还是会发生。当组织选择网络安全时，100%涉及加密技术。密码学在网络安全解决方案中的五个基本用途是:
Confidentiality – Cryptography gives confidentiality through changing or hiding a message and protects confidential data from unauthorized access and use cryptographic key techniques to critically protect data;
Access control – Only authorized users (login & password) can access to protect confidential data etc. Access would be possible for those individual that had access to the correct cryptographic keys; (Mitchell, M, 1995)
Integrity – Cryptographic tools give integrity verify that permit a recipient to authenticate that message transformed and cannot prevent a message from being transformed but effective to identify either planned and unplanned change of the message;
Authentication is the ability to verify who sent a message. It done through the control key because those with access to the key are able to encrypt a message. Cryptographic function use different methods to certify that message is not changed or altered. These hash functions, digital signatures and message authentication codes.
4.Explore encryption for network security探索网络安全的加密
Encryption for network security
Encryption is the most effective method to reduce data loss or theft to encrypt the data on the network security. Encryption is a process of network security to apply crypto services at the network transfer layer on top of the data link level and under the application level. Network encryption other name network layer or network level encryption. The network transfer layers are layers 2 and 4 of the open systems interconnections (OSI) is the reference model, “the layers responsible for connectivity and routing between two end points. Using the existing network services and application software, network encryption is invisible to the end user and operates independently of any other encryption processes used. Data is encrypted only while in transit, existing as plaintext on the originating and receiving hosts”.
网络安全加密
加密是减少数据丢失或被盗的最有效方法，对网络上的数据进行加密安全。加密是在数据链路层之上和应用层之下的网络传输层应用加密服务的网络安全过程。网络加密又称网络层或网络级加密。网络传输层是开放系统互连(OSI)的第2层和第4层，是参考模型，“负责两个端点之间的连接和路由的层”。使用现有的网络服务和应用软件，网络加密对最终用户是不可见的，并且独立于使用的任何其他加密过程运行。数据只在传输过程中被加密，以明文形式存在于原始主机和接收主机上”。
Encryption for network security execute through internet protocol security and set of open internet engineering task force (IETF) standard and apply in combination and build structure for confidential communication over IP networks. Internet protocol security works through the network architecture and encrypted packets show to be the same to unencrypted packets and rout through any IP network easily. Network encryption product and services provide several companies such as Cisco, Oracle etc. (Search security, 2010)
5.Critically review the key and password management in terms of network system security从网络系统安全的角度对密钥和密码管理进行严格的审查
The key management
Information become essential assets and protects it and availability is vital for business success. Encryption is the technology for doing so and become significant part of network system security. Encryption key is very helpful to secure data and information. There are two types of key public and private key use to secure the information and network. These key used in cryptographic system as below:
密钥管理
信息成为必要的资产并保护它，可用性对业务成功至关重要。加密技术正是实现这一目的的技术，成为网络系统安全的重要组成部分。加密密钥对于保护数据和信息非常有帮助。用于保护信息和网络的密钥有两种类型——公钥和私钥。这些密钥在密码系统中使用如下:
Public Key – it was invented in 1976 and refer to cypher architecture type and apply two key pairs is encrypt and decrypt. It can use to encrypt message and corresponding private key to decrypt it. Public key encryption believe extremely secure because it does not need secret shared key among the sender and receiver. It is helpful for keeping private emails and stored on mail servers for many years. It programs such as PGP has digital signature ability built message sent can digitally signed.
Private Key – it also called secret key and encryption/decryption key to exchange secret messages and shared by the communicators so that each can encrypt and decrypt messages. Public key uses with private key together. (Search-security 2010)
Password management
Password is the most important aspect to login into the system and the network. Organisation should allow only authorised users to access to the network and every user access individual login and passwords to enter the network, its result increase the security aspects. There are following necessary things to secure password in the network system as below:
Long Password – every user need to long password because short password can very quickly compromised and analyse the permutation based on the password length;
Change password anytime – employee should change password regularly, nobody assume easily and helpful for security breaches of the network;
Avoid utilize similar password – don’t use the same password for different accounts because it would naive for administrator to think and employee should use different password for safety and security for network system;
Necessity to changing password regularly – employees also gradually more access their work accounts from remote location, user need to educate/awareness on the required of altering the password frequently. (Storts, J, 2010)
6.Compare symmetric and asymmetric encryption systems and their vulnerability to attack比较对称和非对称加密系统及其受攻击的脆弱性
Symmetric encryption systems and their vulnerability
Symmetric encryption system use same secret key is used to encrypt and decrypt information and transform between two keys. Secret key concern to information to transform the content because both can use encrypts and decrypts traffic. Symmetric encryption system has two types are:
对称加密系统及其脆弱性
对称加密系统使用相同的密钥对信息进行加密和解密，并在两个密钥之间进行转换。密钥关系到信息来转换内容，因为两者都可以使用加密和解密通信。对称加密系统有两种类型:
Stream ciphers – it is bits of information one at a time and operates on 1 bit of data at a time. It is faster and smaller to implement and have an important security gap. Certain types of attacks may cause the information to be revealed;
Block ciphers – it is encrypts information by breaking it down into blocks and encrypt data in each block and this data is fixed sized commonly 64 bit and mostly use in triple DES and AES. (Encryptionanddecryption, 2010)
Symmetric encryption algorithms including Des, 3DES, AES, and RC4 etc. 3DES and AES are normally used in IP sec and other types of VPNs. RC4 is used on wireless networks and used by WEP and WPA for encryption. “Symmetric encryption algorithms can be extremely fast, and their relatively low complexity allows for easy implementation in hardware. However, they require that all hosts participating in the encryption have already been configured with the secret key through some external means”. (Stretch, J, 2010)
I conclude that security of wireless network system play key role in every organisation and also implement all network security strategies for the organisation in present and future and secure network resources against alteration, destruction, and unauthorized use. Cryptography tools and web security tools are also very helpful to secure the network system and protect IT assets, confidential data and information.
我的结论是，无线网络系统的安全在每一个组织中都扮演着关键的角色，同时也为组织在现在和未来实施所有的网络安全策略，并确保网络资源不被更改、破坏和未经授权的使用。加密工具和网络安全工具也非常有助于确保网络系统的安全，保护IT资产、机密数据和信息。
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