Encrption Decryption

7/31/2019 Encrption Decryption

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Submitted By :

Chandan Gautam

(CSE A)Reg.No:350074040

Guided By:

L Ramalingam ,Sr. Lecturer

Department of Computer Science Engineering

(AVIT) 1


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Figure 16-2

Plaintext : It is original message ,before beingtransformed .The data are not encrypted.

Ciphertext : After the message is transformed .The data are encrypted.

Alice : Alice is the person who needs to sendsecure data.

Bob : Bob is the recipient of the data.

Eve : Eve is the person who somehow disturbsthe communication between Alice and Bob.

Continued....


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Information is often stored and transmitted in a

file. Encryption algorithm transforms the plain text

into cipher text.

A plain text file uses a common encoding formatsuch as ASCII or UNICODE to represent thecharacter of file.

Encryption is a translation of a file into a format

that hides the content from EVE ;secretcode;ciphertext.

Continued....

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After sending the information by ALICE , BOBreceive the information and decrypt the data.

A decryption algorithm transforms the ciphertextback into plaintext.

For decrypting the data receiver uses three typesof key :

Secret key

Public key

Private key

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PLAINTEXT

CIPHERTEXT

PLAINTEXT

SENDERRECEIVER

EVE

DATA FLOW DIAGRAM


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Two categories :

Symmetric key cryptography

Asymmetric key cryptography

In symmetric key cryptography,the same key isused by the sender(for Encryption) and the

receiver(for Decryption) . In case of symmetric key,the key is shared.

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In asymmetric key cryptography,two types of key isused :

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Alice

Bob


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DES encrypts and decrypts at the bit level. The plaintext are broken into segments of 64 bits.

Each section is encrypted using a 56-bit key. (Fig.16.3) Every bit of ciphertext depends on every bit of

plaintext and the key.

It is very difficult to guess the bits of plaintextfrom the bits of ciphertext.


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Privacy & Secruty : E-mail message,Wirelessnetwork

Confidentiality :Personal records,Transaction

records .

Authentication : Digital signatures,Login.

Intellectual Property : Copy protection

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Advantage Individuals can post their public key on their Web

site.

The number of the keys is only twice of the number

of user. Disadvantage

The complexity of the algorithm: calculating theciphertext from plaintext using the long keys takes

a lot of time.


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CHANDAN GAUTAM

B.E. 3rd Yr CSE

VMU ,AVIT

THANK YOU

Documents

Encrption Decryption