# Cryptography

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## Presentation Transcript

### CRYPTOGRAPHY:

CRYPTOGRAPHY By Miss.Sankh P.S

### CONTENTS :

CONTENTS Introduction History Basic concept Types Ciphers Classical encryption techniques Applications Conclusion

### INTRODUCTION:

INTRODUCTION - Today the Internet is decentralized network of networks. Anyone can coneect to network & can just send about anything. This places burden on every host & organization having network connectivity that they should think about network security. - The CRYPTOGRAPHY is strongest tool to implement security services.

### HISTORY:

HISTORY The first use of cryptography in 1900 B.C. Used by Egyptian scribe Some experts say it appeared right after writing was invented

### BASIC CONCEPT:

BASIC CONCEPT MEANING:- The Greek word CRYPTOGRAPHY means secret writing. crypto –secret & graphy –writing. DEFINATION:- It is art or science which transforms the messages to make them secure & immune to attacks. It transforms normal data into a form that is ununderstable .

### TYPES:

TYPES Two kinds of cryptosystems: Symmetric:-Uses the same key (the secret key) to encrypt and decrypt a message. Asymmetric:-Uses one key (the public key) to encrypt a message and a different key (the private key) to decrypt the message.

HOW IT WORKS!

### TERMS & DEFINITION:

TERMS & DEFINITION plaintext: This is what you want to encrypt. ciphertext: The encrypted output. encryption: The process by which plaintext is converted into ciphertext. encryption algorithm: The sequence of data processing steps that go into transforming plaintext into ciphertext. decryption algorithm: The sequence of data processing steps that go into transforming ciphertext back into plaintext.

### CIPHERS:

CIPHERS This are the methods used for encryption & decryption. block cipher: A block cipher processes a block of input data at a time and produces a ciphertext block of the same size. stream cipher: A stream cipher encrypts data usually one byte at at time.

### Classical encryption techniques:

Classical encryption techniques Classical encryption techniques mainly uses -Substitution -Transposition Substitution means replacing an element of the plaintext with an element of ciphertext. Transposition means rearranging the order of appearance of the elements of the plaintext.

### :

Encryption by using substitution:- Each character of a message is replaced by a another character . Example- three po-sition down in the alphabet. plaintext: are you ready ciphertext: DUH BRX UHDGB

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Encryption using transposition:- In this the position of characters are get changed to get ciphertext. Example- PLAINTEXT: this attack depended on a weakness in the protocol t i h s t a k e e d d n w a n s i t e r t c l a t c d p n e o a e k e s n h p o o o The rails may be taken off in either order for the ciphertext; here we take the first row first: TIATCDPNEOAEKESNHPOOAHSTAKEEDDNWANSITERTCL Breaking into five-letter blocks, we get: TIATC DPNEO AEKES NHPOO AHSTA KEEDD NWANS ITERT CL CIPHERTEXT: TIATC DPNEO AEKES NHPOO AHSTA KEEDD NWANS ITERT CL

### TYPES OF CIPHERS :

TYPES OF CIPHERS -Simple substitution cipher:- 1.caesar cipher 2.swahili angle -Multiple-character substitution cipher:- 1.The Playfair Cipher -Multi-Letter Cipher 1.The Hill Cipher -Polyalphabetic Ciphers 1. The Vigenere Cipher

### APPLICATIONS:

APPLICATIONS 1.File encryption - Files are stored in encrypted form on disk Only owner and other authorized users has the secret key for decrypting the file. 2.Encrypting communication -Communication between browser and web server -Remote shell connection

### Slide 15:

3.Digital Rights Management -Digital Rights Management (DRM) refers to hardware and software systems providing access control for digital content (e.g., music and video files) -DRM aims at preventing the illegal altering, sharing, copying, printing, and viewing of digital media. 4.All types of information on the network can be secured by applying cryptography. For this some cryptography based protocols are used.

Reference Books

### CONCLUSION:

CONCLUSION Cryptographic mechanisms & protocols plays critical role in providing all five security services.Indeed, without cryptography the mechanisms which provides security would not exits.So,Cryptography is important aspect of IT security. But because of complicated nature of cryptographic mechanisms it has limitations.

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