Which of the following BEST describes a chosen plaintext attack?

Question

Options

• AThe cryptanalyst can generate ciphertext from arbitrary text.
• BThe cryptanalyst examines the communication being sent back and forth.
• CThe cryptanalyst can choose the key and algorithm to mount the attack.
• DThe cryptanalyst is presented with the ciphertext from which the original message is determined.

• A
  93% (41)
• B
  2% (1)
• C
  5% (2)

Explanation

According to the CISSP CBK Official Study Guide, a chosen plaintext attack is a type of cryptanalysis that allows the cryptanalyst to generate ciphertext from arbitrary text. A cryptanalysis is the process of breaking or analyzing a cryptographic system or algorithm, by finding the plaintext, the key, or the algorithm from the ciphertext, or by exploiting the weaknesses or vulnerabilities of the system or algorithm. A chosen plaintext attack is a scenario where the cryptanalyst has access to the encryption function or device, and can choose any plaintext and obtain the corresponding ciphertext. A chosen plaintext attack can help the cryptanalyst to deduce the key or the algorithm, or to create a codebook or a dictionary that maps the plaintext to the ciphertext. The cryptanalyst does not examine the communication being sent back and forth, as this would be a ciphertext-only attack, where the cryptanalyst only has access to the ciphertext, and tries to infer the plaintext, the key, or the algorithm from the statistical or linguistic analysis of the ciphertext. The cryptanalyst does not choose the key and algorithm to mount the attack, as this would be a known plaintext attack, where the cryptanalyst has access to some pairs of plaintext and ciphertext that are encrypted with the same key and algorithm, and tries to find the key or the algorithm from the correlation or pattern between the plaintext and the ciphertext. The cryptanalyst is not presented with the ciphertext from which the original message is determined, as this would be a decryption problem, where the cryptanalyst has access to the ciphertext and the key or the algorithm, and tries to recover the plaintext from the ciphertext.

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