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Unit 3-Symmetric Key Crypto_Part3

# Unit 3-Symmetric Key Crypto_Part3 - generated and XORed...

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Unit 3 - 5 Stream Ciphers A stream cipher is one that encrypts a digital data stream one bit or one byte at a time. A stream cipher takes a key K of length n bits and stretches it into a long keystream ( stream cipher function ). To encrypt , this keystream is then XORed with the plaintext P to produce ciphertext C The use of the keystream is identical to the use of the key in a one-time pad cipher. To decrypt with a stream cipher, the same keystream is

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Unformatted text preview: generated and XORed with the ciphertext. Unit 3 - 6 Stream Ciphers, cont. The stream cipher function can be viewed simply as: K is the key, S is the keystream that we’ll use as a one-time pad S is represented as: S = s s 1 s 2 ... The encryption formula is: P = p p 1 p 2 ... is the plaintext, and C = c c 1 c 2 ... is the ciphertext. StreamCipher (K) = S c = p ⊕ s , c 1 = p 1 ⊕ s 1 , c 2 = p 2 ⊕ s 2 , . . ....
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Unit 3-Symmetric Key Crypto_Part3 - generated and XORed...

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