The OSI security architecture Threats Obtaining a user’s certificate Electronic mail security PGP operation confidentiality PGP operation mail compatibility PGP message format Domain keys identification mail

1. NETWORK SECURITY
NAME OF THE STAFF : Mrs. M. FLORANCE DYANA
NAME OF THE STUDENT : S.MAREESWARI,
J.GAYATHRI DEVI,
R.KAVITHA.
REGISTER NUMBER : CB17S 250393
CB17S 250370
CB17S 250383
SUBJECT CODE : P8MCA27
CLASS : III BCA-A
BATCH : 2017-2020
YEAR : 2019-2020

3.  Introduction
 The OSI security architecture
 Threats
 Obtaining a user’s certificate
 Electronic mail security
 PGP operation confidentiality
 PGP operation mail compatibility
 PGP message format
 Domain keys identification mail

4. Introduction to Network Security, Authentication Applications
• Information: is defined as “knowledge obtained from
investigation, Study or Instruction,
• Intelligence, news, facts, data, a Signature or Character
representing data”.
 Security: is defined as “freedom from Danger”, or Safety:
“Freedom from Fear or Anxiety”.
 Information Security: “Measures adopted to prevent the
unauthorized use, misuse,
 modification, Denial of use of knowledge, Facts, data or
Capabilities”.
From the above definition, Information Security does guarantees
protection.
Introduction

5. The OSI security architecture
 The International Telecommunication Union (ITU) Telecommunication Standardization
 Sector (ITU-T) Recommends X.800, Security Architecture for OSI, defines a systematic
 approach. The OSI security architecture provides overview of many of the concepts and it
 focuses on security attacks, mechanisms, and services A second type of passive attack, traffic
analysis, is subtler .
 Suppose that we had a way of masking the contents of messages or other information traffic
so that opponents,
 even if they captured the message, could not extract the information from the message. The
 common technique for masking contents is encryption. If we had encryption protection in
 place, an opponent might still be able to observe the pattern of these messages

7. Threats
 Security Services:
 X.800 defines a security service as a service
provided by a protocol layer of
communicating
 open systems, which ensures adequate
security of the systems or of data transfers.
Also the
 RFC 2828 defines security services as a
processing or communication service that is
 provided by a system to give a specific kind
of protection to system resources.
 Security Services implement security
policies and are implemented by security
mechanisms.
 X.800 divides these services into five
categories and fourteen specific services as
shown in the below Table.

8. Obtaining a user’s certificate
 User certificates generated by a CA have the following characteristics:
 Any user with access to the public key of the CA can verify the user public
key that application.
 Because certificates are unforgeable, they can be placed in a directory without
the need for the directory to make special efforts to protect them taken from
X.509, is an example of hierarchy.
 The directory entry for each CA includes two types of certificates:
 • Forward certificates: Certificates of X generated by other CAs •
 Reverse certificates: Certificates generated by X that are the certificates of
other CAs In this example, user A can acquire the following certificates from
the directory to establish a certification path to B:
 X<<W>> W <<V>> V <<Y>> <<Z>> Z <<B>>

9. Electronic mail security
PGP operation
 Sender creates message
 Make SHA-1 160-bit hash of
message
 Attached RSA signed hash to
message
 Receiver decrypted&
recovers hash code
 Receiver verifies received
message hash
Authentication:

10. PGP operation-confidentiality
 Sender forms 128-bit random
session key
 Encrypts message with
session key
 Attaches session key
encrypted with RSA
 Receivers decrypts& recovers
session key
 Session key is used to
decrypt message

11. PGP operation- Email compatibility
PGP segments message if too big
Email was designed only for text
need to encode binary into printable ASCII characters
Uses radix-64 or base -64 algorithm
Maps 3 bytes to 4 printable chars
PGP produces binary data appends a CRC

13. domain keys identification mail
 Emails signed by the
enterprise , e. g. WUSTL
rather then the sender
 Company’s mail system
signs the message
 So spammers cannot fake
all that companies email
addresses