This presentation will show you the basics of cryptography. Main topics like basic terminology,goals of cryptography,threats,types of cryptography,algorithms of cryptography,etc. are covered in this presentation.If you like this presentation please do hit the like.

1. CRYPTOGRAPHY

2. INTRODUCTION
 Cryptography (from Greek kryptós, "hidden", + gráphein, "to write").
 Cryptography is the practice and study of techniques for secure
communication in the presence of third parties (called adversaries).
 It is about constructing and analysing protocols that
overcome the influence of adversaries.

3.  Cipher: the algorithm that does the encryption.
 Ciphertext: the encrypted (scrambled) version of the message.
Message altered to be unreadable by anyone except the
intended recipients.
 Cryptanalysis: the science of breaking cryptographic algorithms.
 Cryptanalyst: a person who breaks cryptographic codes; also
referred to as “the attacker”.

4.  Cryptosystem – The combination of algorithm, key, and key
management functions used to perform cryptographic
operations.
 Decryption: the process of converting ciphertext back to the
original plaintext.
 Encryption: scrambling a message or data using a specialized
cryptographic algorithm.
 Initialization Vector – Random values used with ciphers to ensure
no patterns are created during encryption.

5.  Key – Sequence that controls the operation and behavior of
the cryptographic algorithm.
 Keyspace – Total number of possible values of keys in a crypto
algorithm.
 Plaintext – A message in its natural format readable by an
attacker.

6. Authentication
 ensures that whoever supplies or accesses sensitive data is an
authorized party.
Confidentiality
 assures that only authorized parties are able to understand
the data.

7. Integrity
 ensures that when a message is sent over a network, the
message that arrives is the same as the message that was
originally sent.
Nonrepudiation
 ensuring that the intended recipient actually received the
message & ensuring that the sender actually sent the
message.

8. THERATES

9.  There are several size of encryption keys:
 64 bit encryption
 128 bit encryption
 256 bit encryption
 512 bit encryption
 1024 bit encryption
 Number indicates the size of the key used to encrypt the message.

10. Symmetric
o Even if an attacker captures the data, the attacker will not be
able to manipulate it in any meaningful way.
o Symmetric algorithms use a single key shared by two
communicating parties.
o The same key is used for both encryption and decryption.
Asymmetric
o Mathematically related key pairs for encryption and
decryption.
o Public and private keys.
Hybrid
o Combines strengths of both methods.
o Asymmetric distributes symmetric key.
10

11. Asymmetric Cryptography
Symmetric Cryptography

12. SUBSTITUTION CIPHER
 A Substitution technique is one in which the letters/numbers/symbols
of plaintext are replaced by other letters/numbers/symbols.
Ex. A D , T z
2 5, 3 6

13. TRANSPOSITION CIPHER
 In this transposition technique the position of
letters/numbers/symbols is changed with one another.
 Plain Text : MEET ME AFTER PARTY
 Cipher Text : TEMEEMEFAPTRYRPT
 Key Used:421635
1 2 3 4 5 6
M E E T M E
A F T E T P
A R T Y
4 2 1 6 3 5
T E M E E M
E F A P T R
Y R P T

14. COMPARISON
SYMMETRIC CRYPTOGRAPHY
 The same algorithm with the same
key is used for encryption and
decryption.
 The Key must be kept secret.
 It may be possible or at least
impractical to decipher a
message if no other information is
available.
ASYMMETRIC
CRYPTOGRAPHY
 One algorithm is used for
encryption and decryption with a
pair of keys , one for encryption
and one for decryption.
 One of the two keys must be kept
secret.
 It may be possible or at least
impractical to decipher a
message if no other information is
available.

15. Types of Symmetric Cryptography:
Stream-based Ciphers
 Mixes plaintext with key stream.
 Good for real-time services.
Block Ciphers
 Substitution and transposition.
 E.g.: DES, AES.

16. Public Key Cryptography
 In public-key cryptosystems, the public key may be
freely distributed, while its paired private key must
remain secret and is used for decryption.
 Public-key cryptography can be used for
implementing digital signature schemes.

17.  Quantum cryptography describes the use of quantum
mechanical effects (in particular quantum
communication and quantum computation) to
perform cryptographic tasks or to break cryptographic
systems.

18.  The advantage of quantum cryptography is that it allows
the completion of various cryptographic tasks that are
proven or conjectured to be impossible using only
classical communication.
 For example, quantum mechanics guarantees that
measuring quantum data disturbs that data. This can be
used to detect eavesdropping in quantum key
distribution.

19.  Digital signatures can be permanently tied to the content of the
message being signed. They cannot then be 'moved' from one
document to another, for any attempt will be detectable.
 RSA and DSA are two of the most popular digital signature
schemes.

20.  In digital signature schemes, there are two
algorithms: one for signing, in which a secret key is
used to process the message and one for
verification, in which the matching public key is
used with the message to check the validity of the
signature.

21. APPLICATION
 Defense services
 Secure data manipulation
 E-commerce
 Business Transaction
 Internet payment system
 User identification system
 Access control
 Data security