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EC-Council

312-50V9 · Question #426

A hacker was able to sniff packets on a company's wireless network. The following information was discovered: The Key 10110010 01001011 The Cyphertext 01100101 01011010 Using the Exlcusive OR, what…

The correct answer is B. 11010111 00010001. XOR decryption recovers the original plaintext by XORing the ciphertext with the key, since XOR is its own inverse operation.

Cryptography

Question

A hacker was able to sniff packets on a company's wireless network. The following information was discovered:

The Key 10110010 01001011 The Cyphertext 01100101 01011010 Using the Exlcusive OR, what was the original message?

Options

  • A00101000 11101110
  • B11010111 00010001
  • C00001101 10100100
  • D11110010 01011011

How the community answered

(25 responses)
  • A
    4% (1)
  • B
    76% (19)
  • C
    8% (2)
  • D
    12% (3)

Why each option

XOR decryption recovers the original plaintext by XORing the ciphertext with the key, since XOR is its own inverse operation.

A00101000 11101110

00101000 11101110 is not the result of XORing the given key and ciphertext values.

B11010111 00010001Correct

XORing the ciphertext (01100101 01011010) with the key (10110010 01001011) byte by byte yields 11010111 00010001, which matches choice B. This works because XOR is self-inverse: if plaintext XOR key = ciphertext, then ciphertext XOR key = plaintext.

C00001101 10100100

00001101 10100100 is not the result of XORing the given key and ciphertext values.

D11110010 01011011

11110010 01011011 is not the result of XORing the given key and ciphertext values.

Concept tested: XOR cipher decryption using key and ciphertext

Topics

#XOR cipher#stream cipher#wireless encryption#ciphertext decryption

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