This document summarizes different cryptography techniques for encrypting and decrypting data during transmission. It discusses symmetric cryptography which uses the same key for encryption and decryption, and asymmetric cryptography which uses a public key to encrypt and private key to decrypt. Specific techniques covered include stream ciphers which encrypt single bits, block ciphers which encrypt fixed-length blocks, transposition ciphers which change character order, and substitution ciphers which substitute plaintext with ciphertext. Public key cryptography is also introduced as using a key pair for encryption and decryption separately. In conclusion, cryptography ensures secure data transmission and transactions over networks by encrypting information.

1. Presented By : Shibani Sarangi
IT Branch, Regd no. 1001289324
Guided By : Prof. X
1
BY
VIDYADHAR VIJJU

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Cryptography
Encryption & Decryption
Transmission Technique
Symmetric Cryptography
Asymmetric Cryptography
Conclusion
References

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Cryptography is the science of using mathematics to encrypt
and decrypt data.
Cryptography enables you to store sensitive information or
transmit it across insecure networks so that it cannot be read by
anyone except the intended recipient.

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encoder
decoder
(plaintext in -
ciphertext out)
ciphertextciphertext
msgmsg
(ciphertext in
- plaintext out)
(should understand
nothingnothing about the msg)
eavesdropper
bla-blabla-bla
cmbcmb--cmbcmb bla-blabla-bla
Cipher
msg
Plain text – in
Cipher text - out
Should understand NOTHING
about the message
Cipher text – in
Plain text - out

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For “secret writing”
To establish a shared secret when other people (eavesdroppers)
are listening.
TYPES
Mainly classified into two types :
1. Symmetric key cryptography
2. Asymmetric key cryptography

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8. BOTH SHOULD
KNOW THE KEY
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In classical cryptography, a transposition cipher changes one
character from the plaintext to another i.e. the order of the
characters is changed.

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Substitution cipher is a method of encryption by which units of
plaintext are substituted with ciphertext according to a regular
system.

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A Stream Cipher is a symmetric or secret-key encryption algorithm
that encrypts a single bit at a time. With a Stream Cipher, the same
plaintext bit or byte will encrypt to a different bit or byte every time it
is encrypted.
e.g. :
Plain text: Pay 100
Binary of plain text: 010111101 (hypothetical)
Key: 100101011 ----- Perform XOR
____________________
Cipher text 110010110 ----- ZTU9^%D
To decrypt make the XOR operation of the cipher text with the
key .

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Block cipher technique involves encryption of one block of text at a
time .Decryption also takes one block of encrypted text at a time.
Length of the block is usually 64 or 128 bits.
e.g. :
Plain text: four and five
Four and five
Key Key Key
wvfa ast wvfa --- cipher text

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Public key cryptography is an asymmetric scheme that uses a Pair of
keys for encryption: a Public key, which encrypts data, and a
corresponding Private key (secret key) for decryption.

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Cryptography, being an art of encrypting and decrypting
confidential information and private messages, should be implemented
in the network security to prevent any leakage and threat.
It can be done by using any of these techniques discussed above for
fortifying the personal data transmission as well as for secure
transaction.

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THANK
YOU
ALL…