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UNIT 1 SECURITY AND PRIVACY ACTIVITY 2 DIGITAL SIGNATURE 4 ESO

UNIT 1 – SECURITY AND INTEGRITY

 

INTRODUCTION

 

In this part of the unit we are talking about how to make sure, he communications through a shared channel, like internet, where there are many bad guys, who might intercept the messages, read and modify them, and even usurp the identity of other people with evil intent.

 

All these elements are meant to make sure the communications from a legal standpoint. This concept is also known as to provide LEGAL SECURITY to the Internet

 

ACTIVITY 2

DIGITAL SIGNATURE

 

1. THE PROBLEM OF THE AUTHENTICATION OF ORIGIN

 

When a communication is carried out through a shared network like Internet, how can you tell that the other part, who could be wherever in the world, is really the one who tells you he is. This problem is very important front the point of view of tasks made on Internet with legal implications. And can be partially solved with the digital signature.

 

 

 

 

2. THE PROBLEM OF INTEGRITY VERIFICATION

 

 

When you receive a document by a shared channel like Internet, how can I make sure that the document is not intercepted and modified by a third part.

 

 

Both problems can be solved using digital signature

 

3. THE DIGITAL SIGNATURE A SOLUTION FOR BOTH PROBLEMS

 

To digitally sign a document is to encrypt it using your private key This allows everybody who knows your public key, and successfully decrypts the document, to ensure that it comes from you. Well, this statement is not totally true. Actually, it ensures that the document comes from the owner of a public key. But, the problem comes when the public key was not delivered personally by the sender to the receiver, face to face. If it was just sent on internet, it is impossible for the receiver to ascertain who was the real sender. Maybe it was sent by a third person. Or maybe the message was intercepted and changed by an usurper. All this may sound to you very unlikely, but while it is technically feasible, the legal consequences might be really serious

 

The digital signature, also ensures that the document was not modified by anybody else while travelling through the network, since the document is encrypted by the sender, any change made by a man in the middle would corrupt it, and turning the decrypt process impossible.

 

As before said, to encrypt a long document using private public key encryption is a very time costing process. So what is actually made is to calculate a HASH from the document and then encrypt it. A Hash is a short character chain obtained from the content of the message through a mathematical funtion. A message always will produce a single and unic hash. Two differente messages, always will produce two different hashes

 

This is the process broken down in its steps.:

 

 

 

 

ACTIVITY 2. SIGNING A DOCUMENT USING KLEOPATRA

 

We are facing the following scenario: We have to send an important file to a classmate. It doesn't matter if a third part reads the document, so it is not necessary to send it encrypted. But for legal reason you want to make sure that the document arrives to him with no modification at all. Your partner also have your public key, delivered in a reliable way. In order to verify the origin and the integrity of this document we must sign it digitally, which means, you have to encrypt its hash with your private key

 

 

Select this option and click on the button next.

 

 

 

 

VERIFY A FILE COMING FROM A CLASSMATE

 

In this part of the activity you must verify the integrity and the authenticate the origin of a file delivered or sent to you by a classmate, Remember, we are assuming that you have installed its public key in the encryption activity, and both files are in the same folder

.

 

Call your teacher in order to assess the activity.

 

CHECKING THE VERIFICATION BY DIGITAL SIGN

 

It's easy to check that the verification worked properly. Just open the file and modify it, adding some word or deleting some letter and save the document.Then perform the verification process again. Now Kleopatra will show this message.

 

 

Felipe Martínez. Dept. Informàtica 9/10

IES EL CABANYAL- VALENCIA

Short url:   http://multidict.net/cs/4497