What is Cryptography?Cryptography derived its name from a Greek word called “Kryptos” which means “Hidden Secrets”.

Cryptography is the practice and study of hiding information. It is the Art or Science of converting a plain intelligible data into an unintelligible data and again retransforming that message into its original form.

It provides Confidentiality, Integrity, Authentication.

HISTORY OF CRYPTOGRAPHY

There are three eras in the history of Cryptography: The Manual era The Mechanical era The Modern era

Manual era refers to Pen and Paper Cryptography and dates back to 2000 B.C.eg : Scytale, Atbash , Caesar, Vigenere.

Mechanical era refers to the invention of cipher machines. E.g.: Japanese Red and Purple Machines , German Enigma.

The modern era of cryptography refers to computers.

There are infinite permutations of cryptography available using computers. E.g.: Lucifer, Rijndael , RSA , ElGamal.

2

What is Encryption / Decryption

Encryption – The process of converting plain text into an unintelligible format

(cipher text) is called Encryption.

Decryption – The process of converting cipher text into a plain text is called

Decryption.

4 Cryptography

Symmetric key Asymmetric

key cryptography cryptography (Public key cryptography)

Classical

Modern cryptography cryptography

Transposition Substitution StreamBlock

cipher cipher cipher cipher

CLASSIFICATION

CRYPTOGRAPHY METHODS

Symmetrico 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.

Classic or Symmetric Cryptography

•have two basic components of classical ciphers: substitution and transposition •in substitution ciphers letters are replaced by other letters •in transposition ciphers the letters are arranged in a different order.

Example:

“Hello world” becomes “ehlol owrdl” is a trivally is a simple rearrangement schemes.

AsymmetricoMathematically related key pairs for encryption and decryption.oPublic and private keys.

PUBLIC KEY or Assymmatric CRYPTOGRAPHY

A form of cryptography in which the key used to encrypt a message differs from the key used to decrypt it.

In public key cryptography, a user has a pair of cryptographic keys—a public key and a private key. The private key is kept secret, while the public key may be widely distributed.

The two main branches of public key cryptography are:

1. Public key encryption 2. Digital signatures

Thank you….