What is utc and why is it used
Course:- Computer Network Security
Reference No.:- EM13693021

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Question 1:

Onmodern networked computers, maintaining the correct time on each machine is important. Computers on a LAN or WAN with different times can cause problems.

In about a page and in your own words explain why it is important for computers to maintaining the correct time and more importantly explain how do they do it.

In your explanation make certain to include discussions on the following linked topics:

• The computer's hardware clock (also called the Real Time Clock or RTC)

• The computer's software clock (also called the kernel or system clock)

• In Linux, how they are syncronised and why do they need to be syncronised? Which is more accurate (with NTP and without NTP)?

• What is UTC and why is it used? (UTC: Coordinated Universal Time, or Temps Universel Coordonné, and if you want-you can explain what is going on with the acronym!)

• What is NTP and what are "clock strata"?

Question 2:

Auser comes to you and explains that she needs some formof encrypted file system to store sensitive information on a Flash drive. The Flash drive will be used to transport the sensitive data between work and home and she is worried about losing the drive and having the data stolen. Both machines, the one at home and the one at work, use the same Linux OS.

She has the following requirements:

• She does not want to encrypt individual files as she has to deal with a large number of files.
• She wants it to be as transparent as possible.
• She thinks she will only need about 128MB at most.
• She wants to also use the flash disk for transporting unencrypted files. Files that can be read on machines apart from her work and home machines.

A 128MB file that contains an encrypted file system, stored on the Flash drive would appear to be ideal-

a. Create a 128MB encrypted file system in a file on a Flash drive so that it can be used with the cryptmount command.

Document and explain in your own words every command you use (plus any command line options) and any configuration files you modify or create. Your descriptions of each operation need to show you understand the purpose of the operation.

Note: If you are uncertain why a particular command or command line option is required-ask! There is at least one step and command line option that you cannot understand from the information in the man page alone! It will require some research and reading up on loop devices and the device mapper.

b. Things you must also address and explain:

• how to ensure that the Flash drive has exactly the samemount point each time it is used on differentmachines.

If it does not have the same mount point then how do you configure the hardwired cryptmount paths?

Hint: Experimentwith "labelled" file-systems (see the command e2label or dosfslabel) or UUIDs in conjunction with the file /etc/fstab

• how to securely manage the file-system encryption keys.

c. Write an instruction sheet for the user so that she can make the modifications to her home machine so that she can access the file on the flash drive containing the encrypted file system. Also explain how she would use the filesystem in her day to-day work.

You may assume that she has root access to be able to configure her home machine so she can mount the encrypted file-system.

You have been asked to install an SVN repository on a server. The SVN will be remotely accessed using the svnserve dæmon that is supplied with SVN (please note that this is not the most secure way to access an SVN repository)

Install the distributed revision control system subversion from the Debian package of the same name. After installation you will need to configure subversion to be usable.

Tasks that will need to be done:

a. Install the subversion package.

b. Write and install a systemd service file to automatically start and stop svnserve (the subversion server) at boot/shutdown (in dæmon mode- do not use inetd mode, do not use an ssh encrypted tunnel).

c. Create an SVN repository at /var/lib/svn/

d. Configure the repository and define the repository usernames and passwords.

e. Implement configuration and runtime options that increase security-explaining why your choices increase security.

f. Test your configuration, repository and running server by creating a project in the repository. Show that you can check in and check out documents from the repository.


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Some of the financial services in the LAN or WAN requires highly accurate timekeeping by the virtual of law.The billing services must know the time accurately and other applications that function in a similar manner.If one need to reduce the chances of confusion in file system then it is very important to ensure that the time used in the LAN is synchronized so as to ensure consistency regardless of what machine the file system are on.

HIPAA and Sarbanes Oxley security rules require accurate time stamping which can only be maintained through ensuring that the time in the LAN is synchronized for all the computer.When people want to track security breaches and network usage or to learn about the problems affecting a large number of components can be nearly impossible if timestamps in logs inaccurate.

In this case, time has always been the critical factor which allows events to be mapped on to others.Different computers can have similar programs that are communicating to each other. If you switch from one computer to another the time should still advance.

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