Illustrate decryption equation

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Reference no: EM132539

Question

Consider a very simple symmetric block encryption algorithm, in which 32-bits blocks of plaintext are encrypted using a 64-bit key. Encryption is definite as
C = (PÅKl)ÄKr

Where C = ciphertext; K = secret key; Kl = leftmost 64 bits of K; Kr = rightmost 64 bits of K; Å =bitwise exclusive or; and Ä is addition mod 264.

(a) Illustrate decryption equation. That is, show equation for P as a function of C, Kl and Kr.

(b) assume an adversary has access to two sets of plaintexts and their corresponding ciphertexts and wishes
to determine K. We have two equations-

C = (PÅKl)ÄKr; C' = (P'ÅKl)ÄKr

Can you solve these two equations to conclude Kl & Kr? If yes, go ahead and solve; if no, explain reason.

Reference no: EM132539

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