Exchanging Data (Do not use)

Question 1

What is RLE and how does it work?

Answer 1

Run Length Encoding. Records a colour value and how many times it repeats.

Question 2

How does dictionary based compression work?

Answer 2

Each unique word is recorded in a dictionary and assigned a number value. The file is then compressed by using that dictionary to replace the text with the relevant numbers. When the compressed file is sent the dictionary is sent with it.

Question 3

What is the Vernam cipher and how does it work?

Answer 3

The only cipher proven to be unbreakable. The encryption key must be longer than the plaintext, be truly random and can only be used once. The key can only be exchanged in person and must be destroyed after it is used.

Question 4

How does symmetric encryption work?

Answer 4

The same key is used to decrypt and encrypt the data. This means the key has to be sent to the same place as the data, which makes it easy to intercept.

Question 5

How does Asymmetric encryption work?

Answer 5

Everybody has two keys, a public key and a private key. A key can be used to encrypt the data, but the same key can’t decrypt it. When data is being sent the sender encrypts the data with the receipient’s public key, so that they can then decrypt it with their private key.

Question 6

What is hashing?

Answer 6

Turns a string into an unreadable format so that you can not get the orginal string back. Used for storing passwords.

Question 7

How does a digital signiture work?

Answer 7

By encrypting a message with your private key, the person you are sending it to knows that it must have come from you as the message can only by decrypted with your public key.

Question 8

What is a digital certificate?

Answer 8

Issued by official certificate authorities and verifies the trustworthiness of a message sender of a website.

Question 9

What is a flat file database?

Answer 9

A database that is made up of a single table.

Question 10

What is a primary key?

Answer 10

A unique identifier for each record in a database

Question 11

What is a secondary key?

Answer 11

A field that is indexed in order to make the database faster to search.

Question 12

What is a foreign Key?

Answer 12

A primary key in another table that is used to link two tables together

Question 13

What is a relational database?

Answer 13

Database made up of multiple tables that are linked together through relationships.

Question 14

What is the first normal form?

Answer 14

There are no repeating attributes.

Question 15

What is the second normal form?

Answer 15

The table must already be in first normal form and the attributes depend entirely on the primary key.

Question 16

What is the third normal form?

Answer 16

The table must already be in the second normal form and all attributes are dependent on the primary key, and nothing but the primary key. If something depends on another attribute in the record, it must be held in a separate table.