1.3 Exchanging Data Flashcards
(19 cards)
Explain two characteristics you would look for in a hashing algorithm used for finding duplicate files by taking a hash of the file and comparing them to a list.
- A low chance of collision to reduce risk of different files being marked as the same.
- Quick to calculate as lots of files need to be hashed.
After running a program that uses hashing to find duplicate files a user finds that they still have apparent duplicates of some of their images. Explain why these apparent duplicates might still be present.
Hashing works on the bits and so two images may appear the same but not be identical at a bit level.
An organisation decides to make a copy of Shakespeare’s entire works available as a downloadable text file from its website. It further decides to compress the file before making it available to download.
State an advantage to the website’s visitors of the file being compressed.
Downloads quicker.
Explain why lossless compression should be used for text files and not lossy.
Lossy takes away some of the information from the original. Lossless preserves all the information from the original. With text the loss of small amounts of information will make it unreadable.
Explain why asymmetric encryption is more suited to transactions over the internet than symmetric encryption.
Symmetric encryption would require both parties to have a copy of the key, this couldn’t be transmitted over the internet or an eavesdropper monitoring the message may see it.
Asymmetric gets round this requirement as there are two different keys.
One key encrypts the data and a different key decrypts it.
Describe what is meant by the term primary key.
A field that has a unique identifier for every record in that table.
A video table consists of the following fields: VideoID, VideoName, Presenter, Topic.
Write an SQL query that finds the name and presenter of all videos on the Topic of “The CPU”.
SELECT VideoName, Presenter
FROM Video
WHERE Topic = “The CPU”
A database stores information about songs on a music streaming service.
One of the tables called Song has the fields: Title, Artist, Genre and Length.
Explain why none of these fields would be suitable as a primary key.
A primary key must have a unique value for every record and the values for all these fields could repeat.
A database stores information about songs on a music streaming service.
One of the tables called Song has the fields: Title, Artist, Genre and Length.
Give one advantage and one disadvantage of indexing the field Artist.
Advantage: Searches of Artist can be performed more quickly.
Disadvantage: The index takes up extra space in the database.
A database stores information about songs on a music streaming service.
One of the tables called Song has the fields: Title, Artist, Genre and Length.
Write an SQL statement that will remove all songs by RandomBits from the table Song.
DELETE FROM Song
WHERE Artist = “RandomBits”
Describe what is meant by the term ‘hash’.
A result generated by applying an algorithm.
Describe one advantage to storing the password as a hash.
Hash functions can’t be reversed. If someone gains access to the database they cannot access the user’s password.
State the use of a bridge.
Provides a link between LANs.
State the use of a gateway.
Provides a link between two dissimilar networks.
Give one advantage and one disadvantage to an architects’ firm of a client-server setup rather than a peer to peer setup.
Advantage: One location to back.
Disadvantage: Central point of failure.
Describe the term ‘firewall’.
A hardware device or piece of software that monitors packets going to and from a network.
State one use of a firewall.
Preventing unauthorised access to a network.
Explain the meaning of the HTML line:
Creates a text box which is referred to as username.
A site’s owner notices that his site doesn’t come up high in the results from a search engine that uses the PageRank algorithm. State what would affect his site’s ranking.
The number of sites that link to their website and the PageRank of the linking sites.
