cryptography
DESCRIPTION
CryptographyTRANSCRIPT
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ON
ON
Cryptography
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WHY DO WE NEED TO SECURE NETWORK ???
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Information needs to be hidden from unauthorized access (confidentiality)
protected from unauthorized change (integrity)
available to an authorized entity when it is needed (availability).
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Symmetry key Encryption
What observation is done here????????(w.r.t locking)
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TRADITIONAL CIPHERS
-> Confidentiality is achieved using ciphers
-> Traditional ciphers are called symmetric-key ciphers (or secret-key ciphers) because the same key is used for encryption and decryption
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General Idea of Traditional ciphers
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Traditional Ciphers
Substitution ciphers Transposition ciphers
A substitution
cipher replaces one symbol with
another.
A transposition
cipher reorders symbols.
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Write row by row
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Plaintext
Ciphertext
Read column by column
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Read row by row
Ciphertext
Write column by column
Plaintext
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Transmission
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Till now we were aware of only “Text” form of the data
What if we want to send audio/ video??????
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Modern CiphersTraditional ciphers• only text
Modern ciphers• numbers• graphics• audio, and video data
Character oriented ciphers
Bit oriented ciphers
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How actually modern ciphers works?Data will be converted to stream of bit
And send the encrypted stream
Encrypt the stream
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Modern block ciphers