The document provides an extensive overview of cryptography, emphasizing the CIA triad—confidentiality, integrity, and availability—as fundamental principles for information security. It contrasts cryptography and steganography, explains various cryptographic methods including symmetric and asymmetric key systems, and details different types of security attacks and mechanisms. Additionally, it describes common encryption techniques and algorithms, highlighting their functionalities and use in ensuring secure communication.

2.  Introduction
 CIA Triad
 Mechanisms of Cryptography
 OSI Security Architecture
 Security Attacks
 Security Mechanisms
 Security Services
 Cryptography vs Steganography
 Network Security Model
 Cryptographic techniques
 Stream Cipher vs Block cipher

3.  Cryptography,a word with Greek origin means “Secret
Writing”
 Cryptography is technique of securing information and
communications through use of codes so that only
those person for whom the information is intended can
understand it and process it. Thus preventing
unauthorized access to information.

5.  These three letters stand for confidentiality, integrity,
and availability, otherwise known as the CIA triad.
 These principles form the cornerstone of any
organization’s security infrastructure
 The CIA triad is so foundational to information
security that anytime data is leaked, a system is
attacked, a user takes a phishing bait, an account is
hijacked, a website is maliciously taken down, or any
number of other security incidents occur, you can be
certain that one or more of these principles has been
violated.

6. Confidentiality
Information can only be accessed by the person for whom it is
intended and no other person except him can access it.
Integrity
Information cannot be modified in storage or transition
between sender and intended receiver without any addition to
information being detected.
Authentication
The identities of sender and receiver are confirmed. As well as
destination/origin of information is confirmed.

7.  Symmetric Key Encipherment/Secret-key
Encipherment
 Asymmetric Key Encipherment/Public-
key Encipherment
 Hashing

8.  It is an encryption system where the sender and
receiver of message use a single common key to
encrypt and decrypt messages.
 Symmetric Key Systems are faster and simpler but
the problem is that sender and receiver have to
somehow exchange key in a secure manner.
 The most popular symmetric key cryptography
system is Data Encryption System(DES).

9. Under this system a pair of keys is used to
encrypt and decrypt information. A public key
is used for encryption and a private key is used
for decryption.
Public key and Private Key are different.
Even if the public key is known by everyone
the intended receiver can only decode it
because he alone knows the private key.

10. A hash value with fixed length is calculated as
per the plain text which makes it impossible
for contents of plain text to be recovered.
Many operating systems use hash functions to
encrypt passwords.

11. ITU-T Recommendation X.800, Security
Architecture for OSI defines systematic way to
defining the requirements for security,
characterizing the approaches to satisfying
those requirements.
 ITU-T – international Telecommunication
Union Telecommunication Standardization
Sector
OSI – Open Systems Interconnections


12.  Security attack: Any actions that compromises the
security of information owned by an organization (or a
person)
 Security mechanism: a mechanism that is designed to
detect, prevent, or recover from a security attack
 Security service: a service that enhances the security
of the data processing systems and the information
transfers of an organization. The services make use of
one or more security mechanisms to provide the
service.

13.  Passive attack: aims to learn or make use of
information from the system but does not affect system
resources.
 Eg:Snooping,Traffic Analysis
 Active attack: attempts to alter system resources or
affect their operation
 Eg: Modification, Masquerading,Replaying,
Repudiation,Denial of Service

14.  Encipherment/Hiding/Covering data
 Data Integrity
 Digital Signature
 Authentication Exchange
 Traffic Padding
 Routing Control
 Notarization
 Access control

15. Data Confidentiality
o Connection confidentiality
o Connectionless Confidentiality
o Selective Field Confidentiality
o Traffic Flow Confidentiality
Authentication
o Peer Entity
o Data Origin

16. Data Integrity
o Connection Integrity with Recovery
o Connection Integrity without Recovery
o Connectionless Integrity
o Selective Field connection Integrity
o Selective Field connectionless Integrity
Non Repudiation: Protection against denial by one of the
entities involved in a communication of having participated in
the communication.
 Proof of origin
 Proof of Destination
 Access Control

18. Cryptography Steganography
In cryptography, sender does not send message
directly to the receiver, before sending information
to the receiver information or plain text is
converted into cipher text by using some
encryption algorithm then send to the receiver and
receiver decrypt the cipher text into plain text to
read the original information.
Steganography is a method in which secret
message is hidden in a cover media.
Cryptography means secret writing. Steganography means covered writing.
In cryptography, structure of data is altered. In steganography, structure of data is not
usually altered.
It is of two types:
1. Symmetric key cryptography 2. Asymmetric key
cryptography
The forms of steganography are:
1. Text 2. Audio 3. Video 4. Images 5.
Network or Protocol
Cryptography
supports Confidentiality and Authentication secu
rity principles as well as Data integrity and Non-
repudiation.
Steganography
supports Confidentiality and Authenticati
on security principles
Cryptography is more popular than Steganography. Steganography is less popular than

19.  Substitution Techniques: The one in
which the letters of plaintext are replaced
by other letters.
◦ Monoalphabetic cipher: In this , a character
or a symbol in plaintext is always changed to
same character or symbol in cipher text
regardless of its position in the text
 Caesar cipher

20. ◦ Polyalphabetic cipher: a substitution cipher
in which the cipher alphabet for the plain
alphabet may be different at different places
during the encryption process.
 Playfair cipher:
 One time Pad cipher
 Vigenere cipher
 Hill cipher
 Autokey cipher:

21. 1. Caesar cipher
 It involves replacing each letter of the alphabet
with the letter standing 3 places further down
the alphabet.

22. 1. Playfair cipher: In Playfair cipher, initially a key table
is created. The key table is a 5×5 grid of alphabets that acts
as the key for encrypting the plaintext. Each of the 25
alphabets must be unique and one letter of the alphabet
(usually J) is omitted from the table as we need only 25
alphabets instead of 26. If the plaintext contains J, then it is
replaced by I.
2.Vigenere cipher: Vigenere Cipher works similar to
Caesar Cipher algorithm with only one major distinction
that it includes key with multiple alphabets shift.

23. 3. Autokey cipher: It is closely related to the Vigenere cipher
but uses a different method of generating the key. In this cipher, the
key is a stream of subkeys which is used to encrypt the corresponding
character in the plaintext.

24. 4.One time Pad cipher: One-time pad cipher is a type of
Vigenere cipher which includes the following features −
 It is an unbreakable cipher.
 The key is exactly same as the length of message which is
encrypted.
 The key is made up of random symbols.
 As the name suggests, key is used one time only and never
used again for any other message to be encrypted.
 Due to this, encrypted message will be vulnerable to attack
for a cryptanalyst. The key used for a one-time pad cipher is
called pad, as it is printed on pads of paper.

25. 5.Hill cipher: Hill cipher is a polygraphic substitution
cipher based on linear algebra. Each letter is represented by
a number modulo 26. Often the simple scheme A = 0, B =
1, …, Z = 25 is used, but this is not an essential feature of
the cipher.
 To encrypt a message, each block of n letters
(considered as an n-component vector) is multiplied by
an invertible n × n matrix, against modulus 26.
 To decrypt the message, each block is multiplied by the
inverse of the matrix used for encryption.
 The matrix used for encryption is the cipher key, and it
should be chosen randomly from the set of invertible n
× n matrices (modulo 26).

26.  Row Transposition Cipher: A transposition cipher
is one which rearranges the order of the letters in the
cipher text (encoded text), according to some
predetermined method, without making any
substitutions.

27.  Feistel Cipher Structure:
• Feistel Cipher model is a structure or a design used to
develop many block ciphers such as DES.
• Same encryption as well as decryption algorithm is
used.
• A separate key is used for each round. However same
round keys are used for encryption as well as
decryption.

28.  Feistel cipher algorithm:
• Create a list of all the Plain Text characters.
• Convert the Plain Text to Ascii and then 8-bit binary
format.
• Divide the binary Plain Text string into two halves:
left half (L1)and right half (R1)
• Generate a random binary keys (K1 and K2) of
length equal to the half the length of the Plain Text
for the two rounds.

30. • First Round of Encryption
• a. Generate function f1 using R1 and K1 as follows:
f1= xor(R1, K1)
• b. Now the new left half(L2) and right half(R2) after round 1 are as
follows:
• R2= xor(f1, L1) L2=R1Second Round of Encryption
• a. Generate function f2 using R2 and K2 as follows:
f2= xor(R2, K2)
• b. Now the new left half(L2) and right half(R2) after round 1 are as
follows:
• R3= xor(f2, L2) L3=R2Concatenation of R3 to L3 is the Cipher
Text
• Same algorithm is used for decryption to retrieve the Plain Text
from the Cipher Text.

31. Stream cipher converts the plain text
into cipher text by taking 1 byte of
plain text at a time.
Block cipher converts the plain text
into cipher text by taking plain text’s
block at a time.
Stream cipher uses 8 bits. Block cipher uses either 64 bits or
more than 64 bits.
It works on substitution techniques
like Caesar cipher, etc.
On the other hand , it works on
transposition techniques like rail-fence
technique, etc
Stream cipher is fast in comparison to
block cipher.
Block cipher is slow

32. Thank you