Download - Cryptography
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Cryptography
WHY DO WE NEED TO SECURE NETWORK ???
Information needs to be hidden from unauthorized access (confidentiality)
protected from unauthorized change (integrity)
available to an authorized entity when it is needed (availability).
Symmetry key Encryption
What observation is done here????????(w.r.t locking)
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
General Idea of Traditional ciphers
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
Till now we were aware of only “Text” form of the data
What if we want to send audio/ video??????
Modern CiphersTraditional ciphers• only text
Modern ciphers• numbers• graphics• audio, and video data
Character oriented ciphers
Bit oriented ciphers
How actually modern ciphers works?Data will be converted to stream of bit
And send the encrypted stream
Encrypt the stream
Modern block ciphers