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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