Vulnerabilities In Link End To End Encryptions Computer Science Essay

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The week 2 discussion board assignment introduces network security vulnerabilities that can appear in E-mail, Web Security, Directory, File Transfer Services and Wireless and Instant Messaging. This paper will discuss if they are any differences between link and end-to-end encryption and identifying the real purpose of traffic padding. Also, stated and explained if there is a difference between a session key and master key.

The main difference between Link encryption and end-to-end encryption is Link encryption. Link encryption means sending an unencrypted message through a secured communication channel (the communication channel itself is encrypted) where the individual sending and receiving the message do not need to take any kind of action because the communication channel does the work for them. For example, communication between two geographically separated corporate offices through a VPN uses link encryption (the VPN provides the encrypted channel).

End-to-end encryption means encrypting the message and sending it through an unsecured communication channel where the individual sending and receiving the message need to take some kind of action to encrypt/decrypt it. For example, encrypting text and sending it through e-mail is end-to-end encryption.

Traffic Padding is used to conceal message contents as well as traffic patterns from attackers. It works by encrypting and transmitting plain text when it's available but in the absence of plain text it continuously produces cipher-text output which is basically random data being generated encrypted and transmitted.

A real live example of link encryption and end-to-end encryption can be thought of in this way. For example, suppose you to want to take a birthday card to your friend on the other side of the street, but she doesn't want anyone to know that it's her birthday. You have two options on how to make sure nobody reads the message. You can write an encoded message on the card (end-to-end encryption) or you can write a normal message on the card and put it in an envelope that only she can open (link encryption). In either case, nobody can read what's written on the card. However, by the size and shape of the card an observer might guess (infer is the fancy term) that it is your friend's birthday. To protect against that you need to hide the shape of the card. If you are using end-to-end encryption (encoded message on the card), you get a card that is larger than a normal birthday card and add a bunch of meaningless nonsense (padding) to the end of your message before you encode it onto the card. If you are using link encryption (message in a secure envelope), you can just use a big, fat, padded envelope (padding) for a normal-sized card. An observer will still see that you are sending a message of some kind, but will have no information to suggest that it is a birthday card.

The difference between a Session Key and Master Key is with a session key - encryption key are made up on the fly and are used to encrypt a communication session. A Master Key is a key that is used to encrypt or create other keys. A session key example is using a Secure Sockets Layer (SSL) website. The steps that will occur when using a SSL

The browser asks the server for a communication session

The browser and the server use the SSL Certificate (asymmetric encryption) to share a one-time use Session Key (symmetric encryption)

All further communication between the browser and the server is encrypted using the Session Key (symmetric encryption) using a scheme such as 3DES

Using a different session key for each session prevents "replay attacks". For an explanation, drop by and we'll talk about it.

A Master Key example - is when individuals keep a list of passwords on their computer in an MS Word or MS Excel document, often setting a password lock on the document. The password used to lock the password list is effectively a Master Key. However, the disadvantage about MS Office document locking: the password hash used to store the password on MS Office documents is very weak. You can easily download a script from the Internet that will crack the password, literally in the blink of an eye.


This paper discussed if they were any differences between link and end-to-end encryption and identifying the real purpose of traffic padding. Also, stated and explained if there was any differences between a session key and master key.

Strong encryption and traffic padding are often used to conceal message contents as well as traffic patterns.

Countermeasure - prevents attacker from learning traffic patterns

Produce ciphertext continuously

If no plain text to encode, send random data

Makes traffic analysis impossible