ClassicCrypto

# The plaintext message is represented using a sequence

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Unformatted text preview: ormation Interchange: – Each character is represented using 7 bits – Total of 128 possibilities – Often an extra bit is used for parity checking, or used for extended characters The One-Time Pad The The one-time pad is an “unbreakable” cryptosystem developed by Vernam and Mauborgne in 1918. The plaintext message is represented using a sequence of bits The key is a random sequence of 0’s and 1’s as long as the message. The ciphertext is the XOR of the plaintext with the key. Example: (message) (key) 00101001 ⊕ 10101100 (ciphertxt ) 10000101 How to decrypt? Just XOR again with the key! Vernam-style Ciphers Vernam The one-time pad belongs to a more general family of stream ciphers known that are often referred to as Vernam-style ciphers In a Vernam cipher – The plaintext x is a sequence of bits – The key sequence k is a sequence of bits – The ciphertext y is generated by y = x⊕k The key sequence is typically generated using a (cryptographic) pseudo-random number generator We will see many choices for generating k later, for now let us look at a popular (but weak) method Linear Feedback Shift Registers Linear Linea...
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## This note was uploaded on 01/07/2013 for the course 332 519 taught by Professor Wadetrappe during the Fall '12 term at Rutgers.

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