15.2 Quiz

Your company produces an encryption device that lets you enter text and receive encrypted text in response. An attacker obtains one of these devices and starts inputting random plain text to see the resulting ciphertext. Which of the following cryptographic attacks is being used?

Chosen plain text

You have a secret key. Bob wants the secret key. He has threatened to harm your reputation at the office if you don't give him the secret key. What type of attack is Bob attempting to use?

Rubber hose attack

Which of the following cryptography attacks is characterized by the attacker having access to both the plain text and the resulting ciphertext, but does not allow the attacker to choose the plain text?

Known plain text

In a ciphertext-only attack, what is the attacker's goal?

To recover the encryption key.

What are the countermeasures used to keep hackers from using various cryptanalysis methods and techniques? (Select two.)

Use passphrases and passwords to encrypt a key stored on disk. Use a key size of 168 bits or 256 bits for symmetric key algorithms.

Which type of cryptanalysis method is based on substitution-permutation networks?

Integral

Which of the following cryptography attacks is characterized by the attacker making a series of interactive queries and choosing subsequent plain texts based on the information from the previous encryption?

Adaptive chosen plain text

Match the types of cryptanalysis with the descriptions.

Finds the affine approximations to the action of a cipher. Linear cryptanalysis A form of cryptanalysis applicable to symmetric key algorithms. Differential cryptanalysis Is useful against block ciphers based on substitution-permutation networks. Integral cryptanalysis It is an extension of differential cryptanalysis. Integral cryptanalysis It is commonly used on block ciphers and works on statistical differences between plain text and ciphertext. Linear cryptanalysis Works on statistical differences between ciphertexts of chosen data. Differential cryptanalysis

Match each cryptography attacks to its description.

The attack repeatedly measured the exact execution times of modular exponentiation operations. = Timing A hacker extracts cryptographic secrets, such as the password to an encrypted file, by coercion or torture. = Rubber hose The hacker makes a series of interactive queries, choosing subsequent plain texts based on the information from the previous encryptions. = Adaptive chosen plain text An attack where a hacker not only breaks a ciphertext but also breaks into a bigger system that is dependent on that ciphertext. = Chosen key The hacker obtains ciphertexts encrypted under two different keys. = Related key The hacker analyzes the plain texts corresponding to an arbitrary set of ciphertexts the hacker chooses. = Chosen ciphertext

Which of the following best explains why brute force attacks are always successful?

They test every possible valid combination.