The document discusses cryptography and its key components. Cryptography is the conversion of data into a secret code for transmission over a public network. It involves encrypting plaintext into ciphertext using an encryption algorithm and key. There are two main types of cryptographic algorithms - symmetric key encryption which uses a single shared key for encryption and decryption, and asymmetric key encryption which uses separate public and private keys. Asymmetric key encryption allows anyone to encrypt messages using the public key, but only the holder of the private key can decrypt them.

1. Presented By:- Akshay Ingole
Date:- 21-2-2019
Cryptography
(κρυπτογράφηση)
S.S.S.K.R. INNANI MAHAVIDYALYA

2. WHAT IS CRYPTOGRAPHY ?
 The conversion of data into a secret code for
transmission over a public network.
 The original text ("plaintext") is turned into a coded
equivalent called "ciphertext" via
an encryption algorithm.

3. COMPONENTS OF A CRYPTOSYSTEM
 Plaintext:- the message before encryption.
 Ciphertext:- the message after encryption.
 Key:-information needed to convert from plain
text to cipher text (or vice-versa).
Function: the encryption or decryption algorithm
used, to encrypt or decrypt message.

4. SECURITY REQUIREMENTS
 Encryption / decryption: transforming
data into something an attacker cannot
understand and vice-versa.
 Authentication: ensures that sender and
receiver are who they are claiming to be
Data integrity: ensure that data is not
changed from source to destination
 Confidentiality: ensures that data is read
only by authorized users

5. TYPES OF CRYPTOGRAPHIC ALGORITHM
There are two types of cryptosystems based on the
manner in which encryption-decryption is carried out in
the system −
 Symmetric Key Encryption
 Asymmetric Key Encryption

6. SYMMETRIC KEY ENCRYPTION
 Uses a single key for both encryption and decryption;
also called private encryption.
 Key is shared by both sender and receiver.
 Both the sender and the receiver use the same secret
keys.

7. ASYMMETRIC KEY ENCRYPTION
 Uses one key for encryption and another for
decryption; also called public encryption.
 asymmetric cryptography involves the use
of two keys:
 a public-key, which may be known by anybody,
and can be used to encrypt messages.
 a private-key, known only to the recipient, used
to decrypt messages,.
 is asymmetric because
 those who encrypt messages or verify signatures
cannot decrypt messages or create signatures

8. Asymmetric key encryption