ISC2 Exam ISSAP Topic 1 Question 56 Discussion

This is used to find patterns in the cryptographic output that might uncover vulnerability or reveal a cryptographic key.

Answer option D is incorrect. In a ciphertext only attack, the attacker obtains encrypted messages that have been encrypted using the same

encryption algorithm. For example, the original version of WEP used RC4, and if sniffed long enough, the repetitions would allow a hacker to

extract the WEP key. Such types of attacks do not require the attacker to have the plaintext because the statistical analysis of the sniffed log

is enough.

Answer option A is incorrect. In a chosen ciphertext attack, the attacker can choose the ciphertext to be decrypted and can then analyze the

plaintext output of the event. The early versions of RSA used in SSL were actually vulnerable to this attack.

Answer option B is incorrect. In a known plaintext attack, the attacker should have both the plaintext and ciphertext of one or more

messages. These two items are used to extract the cryptographic key and recover the encrypted text.