Last Updated on November 21, 2023 by InfraExam

## Which method of cryptanalysis should you use if you only have access to the cipher text messages (all of which have been encrypted using the same encryption algorithm), and want to perform statistical analysis to attempt to determine the potentially weak keys?

- birthday attack
- chosen-plaintext attack
- ciphertext-only attack
- chosen-ciphertext attack

Explanation & Hint:
The method of cryptanalysis you should use if you only have access to the ciphertext messages is the: **ciphertext-only attack**
In a ciphertext-only attack, the attacker has access only to a set of ciphertexts. The attack is carried out by performing statistical analysis on the ciphertexts to find patterns that can be used to deduce the key or plaintext. This kind of attack is based on the assumption that certain characteristics of the plaintext are reflected in the ciphertext and can be discovered without knowing the corresponding plaintext. When multiple messages are encrypted with the same encryption algorithm, and potentially weak or repeated keys are suspected, this method can sometimes be effective, especially if the encryption algorithm has known vulnerabilities to statistical analysis. |