[Apr 21, 2023] 212-81 certification guide Q&A from Training Expert Actual4Cert
212-81 Certification Overview Latest 212-81 PDF Dumps
EC-COUNCIL 212-81 Exam Syllabus Topics:
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NEW QUESTION 106
Which of the following is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel?
- A. Elliptic Curve
- B. Diffie-Hellman
- C. RSA
- D. NMD5
Answer: B
Explanation:
Diffie-Hellman
https://en.wikipedia.org/wiki/Diffie%E2%80%93Hellman_key_exchange
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 originally conceptualized by Ralph Merkle and named after Whitfield Diffie and Martin Hellman. DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography.
Incorrect answers:
Elliptic Curve - Asymmetric Key Algorithm, provides encryption, digital signatures, key exchange, based on the idea of using points on a curve to define the public/private key, used in wireless devices and smart cards. The security of the Elliptic Curve cryptography is based on the fact that finding the discrete logarithm of a random elliptic curve element with respect to a publicly known base point is difficult to the point of being impractical to do so. (y2 = x3 + Ax + B) - Developed by Victor Miller and Neil Koblitz in 1985 MD5 - hash function - Created by Ronald Rivest. Replaced MD4. 128 bit output size, 512 bit block size, 32 bit word size, 64 rounds. Infamously compromised by Flame malware in 2012. Not collision resistant - Not Reversible - RFC 1321 RSA - is a public-key cryptosystem that is widely used for secure data transmission.
NEW QUESTION 107
Frank is trying to break into an encrypted file... He is attempting all the possible keys that could be used for this algorithm. Attempting to crack encryption by simply trying as many randomly generated keys as possible is referred to as what?
- A. Kasiski
- B. Rainbow table
- C. Brute force
- D. Frequency analysis
Answer: C
Explanation:
Brute force
https://en.wikipedia.org/wiki/Brute-force_attack
Brute-force attack consists of an attacker submitting many passwords or passphrases with the hope of eventually guessing correctly. The attacker systematically checks all possible passwords and passphrases until the correct one is found. Alternatively, the attacker can attempt to guess the key which is typically created from the password using a key derivation function. This is known as an exhaustive key search.
Incorrect answers:
Kasiski - Kasiski examination (also referred to as Kasiski's test or Kasiski's method) is a method of attacking polyalphabetic substitution ciphers, such as the Vigenere cipher. It was first published by Friedrich Kasiski in 1863, but seems to have been independently discovered by Charles Babbage as early as 1846.
Rainbow table - is a precomputed table for caching the output of cryptographic hash functions, usually for cracking password hashes. Tables are usually used in recovering a key derivation function (or credit card numbers, etc.) up to a certain length consisting of a limited set of characters. It is a practical example of a space-time tradeoff, using less computer processing time and more storage than a brute-force attack which calculates a hash on every attempt, but more processing time and less storage than a simple key derivation function with one entry per hash. Use of a key derivation that employs a salt makes this attack infeasible.
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.
NEW QUESTION 108
A _____ is a function is not reversible.
- A. Stream cipher
- B. Hash
- C. Asymmetric cipher
- D. Block Cipher
Answer: B
Explanation:
Hash
https://en.wikipedia.org/wiki/Hash_function
Hash functions are irreversible. This is actually required for them to fulfill their function of determining whether someone possesses an uncorrupted copy of the hashed data. This brings susceptibility to brute force attacks, which are quite powerful these days, particularly against MD5.
NEW QUESTION 109
What is Kerchoff's principle?
- A. A minimum of 15 rounds is needed for a Feistel cipher to be secure
- B. A minimum key size of 256 bits is necessary for security
- C. Only the key needs to be secret, not the actual algorithm
- D. Both algorithm and key should be kept secret
Answer: C
Explanation:
Only the key needs to be secret, not the actual algorithm
https://en.wikipedia.org/wiki/Kerckhoffs%27s_principle
Kerckhoffs's principle of cryptography was stated by Netherlands born cryptographer Auguste Kerckhoffs in the 19th century: A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.
NEW QUESTION 110
Denis is looking at an older system that uses DES encryption. A colleague has told him that DES is insecure due to a small key size. What is the key length used for DES?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: C
Explanation:
56
https://en.wikipedia.org/wiki/DES
The Data Encryption Standard 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.
NEW QUESTION 111
The time and effort required to break a security measure.
- A. Work factor
- B. Payload
- C. Session Key
- D. Non-repudiation
Answer: A
Explanation:
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.
NEW QUESTION 112
DES has a key space of what?
- A. 2^192
- B. 2^56
- C. 2^64
- D. 2^128
Answer: B
Explanation:
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.
NEW QUESTION 113
Bob's password is hashed, and so is John's. Even though they used different passwords, the hash is the same. What is this called?
- A. Convergence
- B. Transposition
- C. A collision
- D. A mistake
Answer: C
Explanation:
A collision
https://en.wikipedia.org/wiki/Collision_(computer_science)
A collision or clash is a situation that occurs when two distinct pieces of data have the same hash value, checksum, fingerprint, or cryptographic digest.
NEW QUESTION 114
This hash function 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.
- A. FORK-256
- B. SHA-1
- C. RSA
- D. SHA-256
Answer: A
Explanation:
FORK-256
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.
Incorrect answers:
SHA1 - (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.
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.
SHA-256 - SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001. They are built using the Merkle-Damgard structure, from a one-way compression function itself built using the Davies-Meyer structure from a specialized block cipher. SHA-2 includes significant changes from its predecessor, SHA-1. The SHA-2 family consists of six hash functions with digests (hash values) that are 224, 256, 384 or 512 bits: SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, SHA-512/256
NEW QUESTION 115
A cryptanalysis success where the attacker deduces the secret key.
- A. Total Break
- B. Shannon's Entropy
- C. Information Deduction
- D. Avalanche effect
Answer: A
Explanation:
Total Break
https://en.wikipedia.org/wiki/Cryptanalysis
The results of cryptanalysis can also vary in usefulness. For example, cryptographer Lars Knudsen (1998) classified various types of attack on block ciphers according to the amount and quality of secret information that was discovered:
Total break - the attacker deduces the secret key.
Global deduction - the attacker discovers a functionally equivalent algorithm for encryption and decryption, but without learning the key.
Instance (local) deduction - the attacker discovers additional plaintexts (or ciphertexts) not previously known.
Information deduction - the attacker gains some Shannon information about plaintexts (or ciphertexts) not previously known.
Distinguishing algorithm - the attacker can distinguish the cipher from a random permutation.
Incorrect answers:
Shannon's Entropy - average level of "information", "surprise", or "uncertainty" inherent in the variable's possible outcomes. The concept of information entropy was introduced by Claude Shannon in his 1948 paper "A Mathematical Theory of Communication".
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.
NEW QUESTION 116
Hash. Created by Ronald Rivest. Replaced MD4. 128 bit output size, 512 bit block size, 32 bit word size, 64 rounds. Infamously compromised by Flame malware in 2012.
- A. Keccak
- B. SHA-1
- C. TIGER
- D. MD5
Answer: D
Explanation:
MD5
https://en.wikipedia.org/wiki/MD5
The MD5 message-digest algorithm is a widely used hash function producing a 128-bit hash value. Although MD5 was initially designed to be used as a cryptographic hash function, it has been found to suffer from extensive vulnerabilities. It can still be used as a checksum to verify data integrity, but only against unintentional corruption. It remains suitable for other non-cryptographic purposes, for example for determining the partition for a particular key in a partitioned database.
MD5 was designed by Ronald Rivest in 1991 to replace an earlier hash function MD4, and was specified in 1992 as RFC 1321 Incorrect answers:
TIGER - hash. Created by Ross Anderson and Eli Baham. 192/160/128 bit output size, 512 bit block size, 53 bit word size, 24 rounds.
SHA-1 - Secure Hashing Algorithm. Designed by NSA. 160 bit output size, 512 bit block size, 40 bit word size, 80 rounds.
Keccak - SHA-3 (Secure Hash Algorithm 3) is the latest member of the Secure Hash Algorithm family of standards, released by NIST on August 5, 2015. SHA-3 is a subset of the broader cryptographic primitive family Keccak, designed by Guido Bertoni, Joan Daemen, Michael Peeters, and Gilles Van Assche, building upon RadioGatun.
NEW QUESTION 117
Original, unencrypted information is referred to as ____.
- A. plaintext
- B. ciphertext
- C. cleartext
- D. text
Answer: A
Explanation:
plaintext
https://en.wikipedia.org/wiki/Plaintext
In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. Cleartext usually refers to data that is transmitted or stored unencrypted ("in clear").
NEW QUESTION 118
Which one of the following uses three different keys, all of the same size?
- A. AES
- B. 3DES
- C. DES
- D. RSA
Answer: B
Explanation:
3DES
https://en.wikipedia.org/wiki/Triple_DES
Triple DES (3DES or TDES), officially the Triple Data Encryption Algorithm (TDEA or Triple DEA), is a symmetric-key block cipher, which applies the DES cipher algorithm three times to each data block.
NEW QUESTION 119
John is going to use RSA to encrypt a message to Joan. What key should he use?
- A. Joan's public key
- B. Joan's private key
- C. A shared key
- D. A random key
Answer: A
Explanation:
Joan's public key
https://en.wikipedia.org/wiki/RSA_(cryptosystem)
Suppose Joahn uses Bob's public key to send him an encrypted message. In the message, she can claim to be Alice but Bob has no way of verifying that the message was actually from Alice since anyone can use Bob's public key to send him encrypted messages. In order to verify the origin of a message, RSA can also be used to sign a message.
Suppose Alice wishes to send a signed message to Bob. She can use her own private key to do so. She produces a hash value of the message, raises it to the power of d (modulo n) (as she does when decrypting a message), and attaches it as a "signature" to the message. When Bob receives the signed message, he uses the same hash algorithm in conjunction with Alice's public key. He raises the signature to the power of e (modulo n) (as he does when encrypting a message), and compares the resulting hash value with the message's actual hash value. If the two agree, he knows that the author of the message was in possession of Alice's private key, and that the message has not been tampered with since.
NEW QUESTION 120
A number that is used only one time, then discarded is called what?
- A. Chain
- B. Nonce
- C. IV
- D. Salt
Answer: B
Explanation:
Nonce
https://en.wikipedia.org/wiki/Cryptographic_nonce
A nonce is an arbitrary number that can be used just once in a cryptographic communication. It is similar in spirit to a nonce word, hence the name. It is often a random or pseudo-random number issued in an authentication protocol to ensure that old communications cannot be reused in replay attacks.
NEW QUESTION 121
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