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The EC-COUNCIL 212-81 CES certification exam is a proctored exam that consists of 50 multiple-choice questions. Participants have 2 hours to complete the exam, and the passing score is 70%. The exam is available in English and Japanese, and participants can take the exam at any Pearson VUE testing center worldwide.
NEW QUESTION # 29
If the round function is a cryptographically secure pseudorandom function, then ___________ rounds is sufficient to make the block cipher a pseudorandom permutation.
- A. 0
- B. 1
- C. 2
- D. 3
Answer: C
Explanation:
3
https://en.wikipedia.org/wiki/Feistel_cipher
Michael Luby and Charles Rackoff analyzed the Feistel cipher construction, and proved that if the round function is a cryptographically secure pseudorandom function, with Ki used as the seed, then 3 rounds are sufficient to make the block cipher a pseudorandom permutation, while 4 rounds are sufficient to make it a "strong" pseudorandom permutation (which means that it remains pseudorandom even to an adversary who gets oracle access to its inverse permutation). Because of this very important result of Luby and Rackoff, Feistel ciphers are sometimes called Luby-Rackoff block ciphers.
NEW QUESTION # 30
An authentication method that periodically re-authenticates the client by establishing a hash that is then resent from the client is called ______.
- A. PAP
- B. SPAP
- C. CHAP
- D. EAP
Answer: C
Explanation:
CHAP
https://en.wikipedia.org/wiki/Challenge-Handshake_Authentication_Protocol Challenge-Handshake Authentication Protocol (CHAP) is an identity verification protocol that does not rely on sending a shared secret between the access-requesting party and the identity-verifying party (the authenticator). CHAP is based on a shared secret, but in order to authenticate, the authenticator sends a "challenge" message to the access-requesting party, which responds with a value calculated using a "one-way hash" function that takes as inputs the challenge and the shared secret. The authenticator checks the response against its own calculation of the expected hash value. If the values match, the authentication succeeds, otherwise it fails. Following the establishment of an authenticated connection, the authenticator may send a challenge to the access-requesting party at random intervals, to which the access-requesting party will have to produce the correct response.
Incorrect answers:
EAP - A framework that allows for creation of different ways to provide authentication, such as smart cards SPAP - Shiva Password Authentication Protocol, PAP with encryption for the usernames/passwords that are transmitted.
PAP - Password Authentication Protocol. Used to authenticate users, but is no longer used because the information was sent in cleartext.
NEW QUESTION # 31
A linear congruential generator is an example of what?
- A. A coprime generator
- B. A random number generator
- C. A pseudo random number generator
- D. A prime number generator
Answer: C
Explanation:
A pseudo random number generator
https://en.wikipedia.org/wiki/Linear_congruential_generator
A linear congruential generator (LCG) is an algorithm that yields a sequence of pseudo-randomized numbers calculated with a discontinuous piecewise linear equation. The method represents one of the oldest and best-known pseudorandom number generator algorithms. The theory behind them is relatively easy to understand, and they are easily implemented and fast, especially on computer hardware which can provide modular arithmetic by storage-bit truncation.
NEW QUESTION # 32
Represents the total number of possible values of keys in a cryptographic algorithm or other security measure, such as a password.
- A. Key Clustering
- B. Key Space
- C. Key Schedule
- D. Key Exchange
Answer: B
Explanation:
Key Space
https://en.wikipedia.org/wiki/Key_space_(cryptography)
Algorithm's key space refers to the set of all possible permutations of a key.
To prevent an adversary from using a brute-force attack to find the key used to encrypt a message, the key space is usually designed to be large enough to make such a search infeasible. On average, half the key space must be searched to find the solution.
Another desirable attribute is that the key must be selected truly randomly from all possible key permutations. Should this not be the case, and the attacker is able to determine some factor that may influence how the key was selected, the search space (and hence also the search time) can be significantly reduced. Humans do not select passwords randomly, therefore attackers frequently try a dictionary attack before a brute force attack, as this approach can often produce the correct answer in far less time than a systematic brute force search of all possible character combinations.
NEW QUESTION # 33
Juanita has been assigned the task of selecting email encryption for the staff of the insurance company she works for. The various employees often use diverse email clients. Which of the following methods is available as an add-in for most email clients?
- A. PGP
- B. RSA
- C. DES
- D. Caesar cipher
Answer: A
Explanation:
PGP
https://en.wikipedia.org/wiki/Pretty_Good_Privacy
Pretty Good Privacy (PGP) is an encryption program that provides cryptographic privacy and authentication for data communication. PGP is used for signing, encrypting, and decrypting texts, e-mails, files, directories, and whole disk partitions and to increase the security of e-mail communications. Phil Zimmermann developed PGP in 1991.
NEW QUESTION # 34
Which of the following encryption algorithms relies on the inability to factor large prime numbers?
- A. MQV
- B. RSA
- C. EC
- D. AES
Answer: B
Explanation:
Correct answers: RSA
https://en.wikipedia.org/wiki/RSA_(cryptosystem)
RSA (Rivest-Shamir-Adleman) is a public-key cryptosystem that is widely used for secure data transmission. It is also one of the oldest. The acronym RSA comes from the surnames of Ron Rivest, Adi Shamir, and Leonard Adleman, who publicly described the algorithm in 1977. An equivalent system was developed secretly, in 1973 at GCHQ (the British signals intelligence agency), by the English mathematician Clifford Cocks. That system was declassified in 1997.
In a public-key cryptosystem, the encryption key is public and distinct from the decryption key, which is kept secret (private). An RSA user creates and publishes a public key based on two large prime numbers, along with an auxiliary value. The prime numbers are kept secret. Messages can be encrypted by anyone, via the public key, but can only be decoded by someone who knows the prime numbers.
The security of RSA relies on the practical difficulty of factoring the product of two large prime numbers, the "factoring problem". Breaking RSA encryption is known as the RSA problem. Whether it is as difficult as the factoring problem is an open question. There are no published methods to defeat the system if a large enough key is used.
Incorrect answers:
EC - Elliptic-curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys compared to non-EC cryptography (based on plain Galois fields) to provide equivalent security.
AES - Advanced Encryption Standard (AES), also known by its original name Rijndael, is a specification for the encryption of electronic data established by the U.S. National Institute of Standards and Technology (NIST) in 2001.
AES is a subset of the Rijndael block cipher developed by two Belgian cryptographers, Vincent Rijmen and Joan Daemen, who submitted a proposal to NIST during the AES selection process. Rijndael is a family of ciphers with different key and block sizes. For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.
MQV - (Menezes-Qu-Vanstone) is an authenticated protocol for key agreement based on the Diffie-Hellman scheme. Like other authenticated Diffie-Hellman schemes, MQV provides protection against an active attacker. The protocol can be modified to work in an arbitrary finite group, and, in particular, elliptic curve groups, where it is known as elliptic curve MQV (ECMQV).
NEW QUESTION # 35
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?
- A. Complex mathematics to conceal a message
- B. Applying keys to a message to conceal it
- C. Changing a message using complex mathematics
- D. Changing a message so it can only be easily read by the intended recipient
Answer: D
Explanation:
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.
NEW QUESTION # 36
Uses a formula, M_n = 2^n - 1 where n is a prime number, to generate primes. Works for 2, 3, 5, 7 but fails on 11 and on many other n values.
- A. Mersenne Primes
- B. Even Numbers
- C. Co-prime Numbers
- D. Fibonacci Numbers
Answer: A
Explanation:
Correct answers: Mersenne Primes
https://en.wikipedia.org/wiki/Mersenne_prime
Mersenne prime is a prime number that is one less than a power of two. That is, it is a prime number of the form M_n = 2^n - 1 for some integer n. They are named after Marin Mersenne, a French Minim friar, who studied them in the early 17th century. If n is a composite number then so is 2^n - 1. Therefore, an equivalent definition of the Mersenne primes is that they are the prime numbers of the form M_p = 2^p - 1 for some prime p.
Incorrect answers:
Even Numbers - A formal definition of an even number is that it is an integer of the form n = 2k, where k is an integer; it can then be shown that an odd number is an integer of the form n = 2k + 1 (or alternately, 2k - 1). It is important to realize that the above definition of parity applies only to integer numbers, hence it cannot be applied to numbers like 1/2 or 4.201. See the section "Higher mathematics" below for some extensions of the notion of parity to a larger class of "numbers" or in other more general settings.
Fibonacci Numbers - commonly denoted F_n, form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1.
Co-prime Numbers - two integers a and b are said to be relatively prime, mutually prime, or coprime if the only positive integer (factor) that evenly divides both of them is 1. Consequently, any prime number that divides one of a or b does not divide the other. This is equivalent to their greatest common divisor (gcd) being 1.
NEW QUESTION # 37
As a network administrator, you have implemented WPA2 encryption in your corporate wireless network. The WPA2's ________ integrity check mechanism provides security against a replay attack.
- A. CRC-32
- B. CRC-MAC
- C. CBC-32
- D. CBC-MAC
Answer: D
Explanation:
CBC-MAC
https://en.wikipedia.org/wiki/CBC-MAC
A cipher block chaining message authentication code (CBC-MAC) is a technique for constructing a message authentication code from a block cipher. The message is encrypted with some block cipher algorithm in CBC mode to create a chain of blocks such that each block depends on the proper encryption of the previous block. This interdependence ensures that a change to any of the plaintext bits will cause the final encrypted block to change in a way that cannot be predicted or counteracted without knowing the key to the block cipher. Using in WPA2 for integrity check and provides security against a replay attack.
NEW QUESTION # 38
Which of the following would be the fastest.
- A. DH
- B. AES
- C. RSA
- D. EC
Answer: B
Explanation:
AES
https://en.wikipedia.org/wiki/Symmetric-key_algorithm
AES - symmetric cipher. Symmetric keys use the same key for both encryption and decryption. Both the sender and receiver of the data must know and share the secret key. For standard encrypt/decrypt functions, symmetric algorithms generally perform much faster than their asymmetrical counterparts. This is due to the fact that asymmetric cryptography is massively inefficient. Symmetric cryptography is designed precisely for the efficient processing of large volumes of data. In other words, symmetric encryption is generally used for speed and performance, e.g. when there's a large amount of data that needs to be encrypted/protected.
Incorrect answers:
RSA - asymmetric cipher,
DH - Diffie-Hellman key exchange is a method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman.
EC - Elliptic-curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields.
NEW QUESTION # 39
A technique used to increase the security of block ciphers. It consists of steps that combine the data with portions of the key (most commonly using a simple XOR) before the first round and after the last round of encryption.
- A. Key Clustering
- B. Whitening
- C. Key Schedule
- D. Key Exchange
Answer: B
Explanation:
Whitening
https://en.wikipedia.org/wiki/Key_whitening
In cryptography, key whitening is a technique intended to increase the security of an iterated block cipher. It consists of steps that combine the data with portions of the key.
The most common form of key whitening is xor-encrypt-xor -- using a simple XOR before the first round and after the last round of encryption.
The first block cipher to use a form of key whitening is DES-X, which simply uses two extra 64-bit keys for whitening, beyond the normal 56-bit key of DES. This is intended to increase the complexity of a brute force attack, increasing the effective size of the key without major changes in the algorithm. DES-X's inventor, Ron Rivest, named the technique whitening.
Incorrect answers:
Key Clustering - different encryption keys generated the same ciphertext from the same plaintext message.
Key Schedule - an algorithm for the key that calculates the subkeys for each round that the encryption goes through.
Key Exchange - a method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm.
NEW QUESTION # 40
Which one of the following is an algorithm that uses variable length key from 1 to 256 bytes, which constitutes a state table that is used for subsequent generation of pseudorandom bytes and then a pseudorandom string of bits, which is XORed with the plaintext to produce the ciphertext?
- A. Blowfish
- B. Twofish
- C. PIKE
- D. RC4
Answer: D
Explanation:
RC4
https://en.wikipedia.org/wiki/RC4
RC4 (Rivest Cipher 4 also known as ARC4 or ARCFOUR meaning Alleged RC4, see below) is a stream cipher. While it is remarkable for its simplicity and speed in software, multiple vulnerabilities have been discovered in RC4, rendering it insecure. It is especially vulnerable when the beginning of the output keystream is not discarded, or when nonrandom or related keys are used. Particularly problematic uses of RC4 have led to very insecure protocols such as WEP.
The key-scheduling algorithm is used to initialize the permutation in the array "S". "keylength" is defined as the number of bytes in the key and can be in the range 1 ≤ keylength ≤ 256, typically between 5 and 16, corresponding to a key length of 40 - 128 bits. First, the array "S" is initialized to the identity permutation. S is then processed for 256 iterations in a similar way to the main PRGA, but also mixes in bytes of the key at the same time.
Incorrect answers:
Blowfish - has a 64-bit block size and a variable key length from 32 bits up to 448 bits. It is a 16-round Feistel cipher and uses large key-dependent S-boxes. In structure it resembles CAST-128, which uses fixed S-boxes.
Twofish - is a symmetric key block cipher with a block size of 128 bits and key sizes up to 256 bits.
PIKE - stream cipher was invented by Ross Anderson to be a "leaner and meaner" version of FISH after he broke FISH in 1994. Its name is supposed to be a humorous allusion to the pike fish.
NEW QUESTION # 41
Which of the following Secure Hashing Algorithm (SHA) produces a 160-bit digest from a message with a maximum length of (264-1) bits and resembles the MD5 algorithm?
- A. SHA-1
- B. SHA-3
- C. SHA-0
- D. SHA-2
Answer: A
Explanation:
SHA-1
https://en.wikipedia.org/wiki/SHA-1
SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest - typically rendered as a hexadecimal number, 40 digits long. It was designed by the United States National Security Agency, and is a U.S. Federal Information Processing Standard.
SHA-1 produces a message digest based on principles similar to those used by Ronald
L. Rivest of MIT in the design of the MD2, MD4 and MD5 message digest algorithms, but generates a larger hash value (160 bits vs. 128 bits).
NEW QUESTION # 42
What size block does FORK256 use?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: B
Explanation:
512
https://en.wikipedia.org/wiki/FORK-256
FORK-256 was introduced at the 2005 NIST Hash workshop and published the following year.[6] FORK-256 uses 512-bit blocks and implements preset constants that change after each repetition. Each block is hashed into a 256-bit block through four branches that divides each 512 block into sixteen 32-bit words that are further encrypted and rearranged
NEW QUESTION # 43
The art and science of writing hidden messages so that no one suspects the existence of the message, a type of security through obscurity. Message can be hidden in picture or audio file for example. Uses least significant bits in a file to store data.
- A. Avalanche effect
- B. Key Schedule
- C. Cryptosystem
- D. Steganography
Answer: D
Explanation:
Steganography
https://en.wikipedia.org/wiki/Steganography
Steganography is the practice of concealing a file, message, image, or video within another file, message, image, or video.
The first recorded use of the term was in 1499 by Johannes Trithemius in his Steganographia, a treatise on cryptography and steganography, disguised as a book on magic. Generally, the hidden messages appear to be (or to be part of) something else: images, articles, shopping lists, or some other cover text. For example, the hidden message may be in invisible ink between the visible lines of a private letter. Some implementations of steganography that lack a shared secret are forms of security through obscurity, and key-dependent steganographic schemes adhere to Kerckhoffs's principle.
Incorrect answers:
Avalanche effect - the desirable property of cryptographic algorithms, typically block ciphers and cryptographic hash functions, wherein if an input is changed slightly (for example, flipping a single bit), the output changes significantly (e.g., half the output bits flip). In the case of high-quality block ciphers, such a small change in either the key or the plaintext should cause a drastic change in the ciphertext.
Cryptosystem - a suite of cryptographic algorithms needed to implement a particular security service, most commonly for achieving confidentiality (encryption) Key Schedule - an algorithm for the key that calculates the subkeys for each round that the encryption goes through.
NEW QUESTION # 44
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The EC-COUNCIL 212-81 Certification Exam is designed for individuals who are involved in securing data and systems against cyber threats. This certification is ideal for IT professionals who are responsible for designing, implementing, and managing encryption solutions in their organizations. The certification exam assesses the candidate's ability to understand and apply encryption concepts, principles, and practices to protect sensitive data from unauthorized access or theft. Moreover, this certification is recognized globally and is highly sought after by employers who require skilled professionals in the area of encryption.
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