The Domain Name System

Question 1

Why is the DNS essential for e-commerce?

Answer 1

Because the DNS allows you to work not in numerical spaces but symbolic ones. It would be impossible to remember IP addresses in numerical form.

Question 2

What did people use to do before the DNS became reliable?

Answer 2

People would have a notebook of IP addresses

Question 3

What is the Domain Name System?

Answer 3

A system that connects textual strings to numbers

Question 4

How must a DNS be?

Answer 4

The DNS must be:
1 scalable;
2 efficient;
3 reliable;
4 maintainable

Question 5

What does it mean that a DNS is scalable?

Answer 5

it must cope with all hosts

The DNS achieves scalability by organising a large number of servers in a hierarchical fashion

Question 6

What does it mean that a DNS is efficient?

Answer 6

it must not delay any host

Question 7

What does it mean that a DNS is reliable?

Answer 7

it must not be a single point of

failure.

Question 8

What does it mean that a DNS is maintainable?

Answer 8

it is constantly updated

Question 9

How many root servers are there?

Answer 9

13

Question 10

Example of top-level domain server.

Answer 10

There are many top-level domain servers for “.com”, “.org”, “.uk”, “.biz

Question 11

What is an authoritative web server?

Answer 11

a server for every organisation with a

publically-accessible Web or mail server. they are machines at organizational level.

Question 12

How does a DNS achieve efficiency?

Answer 12

By local server caching. This enables a server to not to go through the DNS tree

Question 13

How does a DNS achieve maintainability?

Answer 13

Authoritative domain servers can be registered, updated and deregistered automatically.
So when an internal mapping is changed the update gets propagated.

Question 14

What may be a problem with trusted DNS services?

Answer 14

A trusted DNS server may not be so trustworthy! It may
promote some policy or business relationship.
It the service gets hacked all services depending on it will be taken out.

Question 15

What was the BOT used to fire at the DYN DNS servers?

Answer 15

MARAI

Question 16

DNSSEC

Answer 16

Domain Name System Security Extensions

Previously there was no way to know id a DNS was secure. Then the DNSSEC was introduced.
So the DNSSEC is a security extension so responses are authenticated but not encrypted.

Question 17

Asymmetric encryption encryption

Answer 17

In asymmetric encryption, the encryption is done with the public key of the receiver

Question 18

Asymmetric encryption decryption

Answer 18

In asymmetric encryption, decryption is done with the private key of the receiver.

Question 19

What does a hash function do?

Answer 19

A hash function takes a string, 𝑀, an returns a number,

𝐻(𝑀).

Question 20

How does DNS improve security?

Answer 20

A sender signs a message by attaching its hash, encrypted with their private key.
It is the opposite of normal encryption You send something encrypted with a private key and decrypt it with the public key.