CRYPTOGRAPHY & NETWORK SECURITY

1. EMAIL SECURITY

2. SHIVA AYYADURAI

3. FIREWALL
Firewalls filter traffic and lower the risk that
malicious packets traveling over the network.

4. WHAT YOU CAN DO WITH FIREWALL
1) Web Filtering
2) Bandwidth Filtering
3) Logging Information
4) In Built DHCP Server
5) VPN etc.

5. SCREENSHOTS OF OUR COLLEGE
FIREWALL

6. SCREENSHOTS OF OUR COLLEGE
FIREWALL

7. SCREENSHOTS OF OUR COLLEGE
FIREWALL

8. ACL
It stands for Access Control List.
An ACL has separate inbound and outbound
rules, and each rule can either allow or deny
traffic.

9. EAMPLE OF ACL
User : Student
Site : Youtube.com
Source: LAN
Destination: WAN
Network: Any
Allow or Deny

10. TCP CONNECTION ESTABLISHMENT
(OR) 3 WAY HANDSHAKE
It is defined as whenever a computer is about to
communicate with any foreign device ( Server,
modem etc) it needs to handshake (or) to
establish a connection with it.
In 3 way handshake SYNC, SYNC+ACK and ACK
are used.
In 2 way handshake FIN and ACK are used.

12. TCP CONNECTION TERMINATION

14. DNS
DNS stands for Domain Name Service which
converts Domain Names into IP Address.
(Ex) Analogy of Telephone Book

15. Rules for Domain Name
1) Each Label (i.e.) Domain Name (.com, .edu,
.in) should not exceed 63 Characters.
2) The full domain name should not exceed 253
Characters (www.twitter.com)
3) The Domain Names are Case Independent
one (It can either Upper Case (or) Lower Case
Letters).

16. Rules for Domain Name
4) The Domain Name can be Letters, Digits,
Hyphen (www.kcet123-vnr.org). This is called
LDH Rule.

17. World famous registers for Domain
Names
1) GoDaddy.com
2) Name cheap.com
3) 1&1 Internet.com
4) Dotster.com

18. ICMP
Stands for "Internet Control Message Protocol“
If there is a problem with the Internet
connection, error and status messages
regarding the connection are sent using ICMP

19. COMMON ERROR MESSAGES

20. COMMON ERROR MESSAGES

21. COMMON ERROR MESSAGES

22. COMMON ERROR MESSAGES

23. PORT NUMBER
A port number is to uniquely identify a specific
process or application in the network.
Types of Port Number
1) Ephemeral Port Number
2) Reserved Port Number

24. RANKING OF EMAIL

25. STRUCTURE OF EMAIL

26. STRUCTURE OF EMAIL
It consists of the following parts such as
1) Header
2) Body
3) To,cc (Carbon Copy), bcc (Blind Carbon Copy)

27. ABOUT SMTP
It stands for Simple Mail Transfer Protocol.
It is used to transfer email from one user to
another.

28. OPERATION OF SMTP

29. LIMITATION OF SMTP
1) SMTP Cannot transmit executable files.
2) SMTP Cannot transmit data in their national
languages (i.e. we can’t send mail in Hindi or
tamil).
3) SMTP rejects message when it exceed the
certain size.
4) It doesn’t supports any animation in their
signature (or) in the body part.

30. MIME
It stands for Multi Purpose Internet Mail Extension.
It supports Non-text attachments such as audio,
video, images, application programs (apk) etc.
Header and Body information in their national
language itself.
It supports gif extension (or) It supports animation
in the body part.

31. MIME

32. POP
It stands for Post Office Protocol.
It is used to retrieve an e-mail from a
mail server.
Incoming messages are stored at a
POP server until the user logs in and view the
message.

33. DISADVANTAGES OF POP
1) It does not POP supports flags on the server
to keep track of message state:
(Ex) whether the message has been read or not,
replied to, or deleted.
2) With POP, no synchronize among multiple
devices. (Ex) Viewing in PC, Tab etc.

34. SYNCHRONISATION IS NOT POSSIBLE
IN POP

35. IMAP
It stands for Internet Message Access Protocol
(IMAP) for accessing email on a remote server
from a local client.

36. SYNCHRONISATION IS POSSIBLE IN
IMAP

37. SYNCHRONISATION IS POSSIBLE IN
IMAP

39. TLS

40. TLS
Transport Layer Security (TLS) is a protocol that
provides privacy and data integrity between
two communicating applications.
When a server and client communicate, TLS
protocol ensures that no third party may
eavesdrop, tamper with any message, and
message forgery.

41. TLS

42. TLS