2^56 https://en.wikipedia.org/wiki/Data_Encryption_Standard The Data Encryption Standard (DES) is a symmetric-key algorithm for the encryption of digital data. Although its short key length of 56 bits makes it too insecure for applications, it has been highly influential in the advancement of cryptography.
Question 57
The time and effort required to break a security measure.
Correct Answer: B
Work factor Work factor - the time and effort required to break a security measure. Incorrect answers: Non-repudiation - involves associating actions or changes with a unique individual. Session Key - is a single-use symmetric key used for encrypting all messages in one communication session. A closely related term is content encryption key (CEK), traffic encryption key (TEK), or multicast key which refers to any key used for encrypting messages, contrary to other uses like encrypting other keys (key encryption key (KEK) or key wrapping key). Payload - is the part of transmitted data that is the actual intended message. Headers and metadata are sent only to enable payload delivery.
Question 58
If you use substitution alone, what weakness is present in the resulting cipher text?
Correct Answer: C
It maintains letter and word frequency https://en.wikipedia.org/wiki/Frequency_analysis Frequency analysis (also known as counting letters) is the study of the frequency of letters or groups of letters in a ciphertext. The method is used as an aid to breaking classical ciphers. Frequency analysis is based on the fact that, in any given stretch of written language, certain letters and combinations of letters occur with varying frequencies. Moreover, there is a characteristic distribution of letters that is roughly the same for almost all samples of that language. For instance, given a section of English language, E, T, A and O are the most common, while Z, Q, X and J are rare. Likewise, TH, ER, ON, and AN are the most common pairs of letters (termed bigrams or digraphs), and SS, EE, TT, and FF are the most common repeats. The nonsense phrase "ETAOIN SHRDLU" represents the 12 most frequent letters in typical English language text. In some ciphers, such properties of the natural language plaintext are preserved in the ciphertext, and these patterns have the potential to be exploited in a ciphertext-only attack.
Question 59
A cipher is defined as what
Correct Answer: A
The algorithm(s) needed to encrypt and decrypt a message https://en.wikipedia.org/wiki/Cipher In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption-a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message; however, the concepts are distinct in cryptography, especially classical cryptography.
Question 60
John is trying to explain the basics of cryptography to a group of young, novice, security students. Which one of the following most accurately defines encryption?
Correct Answer: D
Changing a message so it can only be easily read by the intended recipient https://en.wikipedia.org/wiki/Encryption Encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decipher a ciphertext back to plaintext and access the original information. Encryption does not itself prevent interference but denies the intelligible content to a would-be interceptor.
