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EC-COUNCIL 212-81 Exam Syllabus Topics:
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NEW QUESTION 30
If you wished to see a list of revoked certificates from a CA, where would you look?
- A. CA
- B. RFC
- C. RA
- D. CRL
Answer: D
Explanation:
CRL
https://ru.wikipedia.org/wiki/Certificate_Revocation_List
Certificate Revocation List (or CRL) is "a list of digital certificates that have been revoked by the issuing certificate authority (CA) before their scheduled expiration date and should no longer be trusted".
Incorrect answers:
RA - Used to proxy the certificate requests on behalf of the user and validate whether or not they are legitimate instead of having the user go directly to the CA. The RA talks to the subordinate CA on behalf of the user, which makes it harder for the actor to get directly to the certificate authority and do harm.
RFC - Request for Comments (RFC) is a publication from the Internet Society (ISOC) and its associated bodies, most prominently the Internet Engineering Task Force (IETF), the principal technical development and standards-setting bodies for the Internet.
CA - certificate authority or certification authority is an entity that issues digital certificates
NEW QUESTION 31
Numbers that have no factors in common with another.
- A. Co-prime numbers
- B. Fibonacci Numbers
- C. Even Numbers
- D. Mersenne Primes
Answer: A
Explanation:
Correct answers: Co-prime numbers
https://en.wikipedia.org/wiki/Coprime_integers
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.
The numerator and denominator of a reduced fraction are coprime. The numbers 14 and 25 are coprime, since 1 is their only common divisor. On the other hand, 14 and 21 are not coprime, because they are both divisible by 7.
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.
Mersenne Primes - 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.
NEW QUESTION 32
A non-secret binary vector used as the initializing input algorithm for encryption of a plaintext block sequence to increase security by introducing additional cryptographic variance.
- A. Salt
- B. Nonce
- C. IV
- D. L2TP
Answer: C
Explanation:
IV
https://en.wikipedia.org/wiki/Initialization_vector
In cryptography, an initialization vector (IV) or starting variable (SV) is a fixed-size input to a cryptographic primitive that is typically required to be random or pseudorandom. Randomization is crucial for encryption schemes to achieve semantic security, a property whereby repeated usage of the scheme under the same key does not allow an attacker to infer relationships between segments of the encrypted message. For block ciphers, the use of an IV is described by the modes of operation. Randomization is also required for other primitives, such as universal hash functions and message authentication codes based thereon.
Incorrect answers:
L2TP - PPTP combined with L2F (Layer 2 Forwarding) (Cisco proprietary protocol) - Uses EAP, CHAP, MS-CHAP, PAP, or S-PAP for authentication. IPSec is used to provide encryption.
Salt - random bits of data intermixed with the message that is to be hashed.
Nonce - 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. They can also be useful as initialization vectors and in cryptographic hash functions.
NEW QUESTION 33
Which one of the following is a component of the PKI?
- A. TGS
- B. OCSP
- C. TGT
- D. CA
Answer: D
Explanation:
CA
https://en.wikipedia.org/wiki/Certificate_authority
Certificate authority or certification authority (CA) is an entity that issues digital certificates. A digital certificate certifies the ownership of a public key by the named subject of the certificate. This allows others (relying parties) to rely upon signatures or on assertions made about the private key that corresponds to the certified public key. A CA acts as a trusted third party-trusted both by the subject (owner) of the certificate and by the party relying upon the certificate. The format of these certificates is specified by the X.509 or EMV standard.
NEW QUESTION 34
Hash algortihm created by the Russians. Produces a fixed length output of 256bits. Input message is broken up into 256 bit blocks. If block is less than 256 bits then it is padded with 0s.
- A. GOST
- B. FORK-256
- C. TIGER
- D. BEAR
Answer: A
Explanation:
GOST
https://en.wikipedia.org/wiki/GOST_(hash_function)
The GOST hash function, defined in the standards GOST R 34.11-94 and GOST 34.311-95 is a 256-bit cryptographic hash function. It was initially defined in the Russian national standard GOST R 34.11-94 Information Technology - Cryptographic Information Security - Hash Function. The equivalent standard used by other member-states of the CIS is GOST 34.311-95.
Incorrect answers:
BEAR - BEAR block cipher was invented by Ross Anderson and Eli Biham by combining a stream cipher and a cryptographic hash function.
TIGER - is a cryptographic hash function designed by Ross Anderson and Eli Biham in 1995 for efficiency on 64-bit platforms. The size of a Tiger hash value is 192 bits. Truncated versions (known as Tiger/128 and Tiger/160) can be used for compatibility with protocols assuming a particular hash size. Unlike the SHA-2 family, no distinguishing initialization values are defined; they are simply prefixes of the full Tiger/192 hash value.
FORK-256 - is a hash algorithm designed in response to security issues discovered in the earlier SHA-1 and MD5 algorithms. After substantial cryptanalysis, the algorithm is considered broken.
NEW QUESTION 35
What does the OCSP protocol provide?
- A. Revoked certificates
- B. Encryption
- C. Hashing
- D. VPN connectivity
Answer: A
Explanation:
Revoked certificates
https://en.wikipedia.org/wiki/Online_Certificate_Status_Protocol
The Online Certificate Status Protocol (OCSP) is an Internet protocol used for obtaining the revocation status of an X.509 digital certificate.It is described in RFC 6960 and is on the Internet standards track. It was created as an alternative to certificate revocation lists (CRL), specifically addressing certain problems associated with using CRLs in a public key infrastructure (PKI). Messages communicated via OCSP are encoded in ASN.1 and are usually communicated over HTTP. The "request/response" nature of these messages leads to OCSP servers being termed OCSP responders.
NEW QUESTION 36
Which analysis type is based on the statistics of the numbers of unique colors and close-color pairs in a 24-bit image, a method that analyzes the pairs of colors created by LSB embedding?
- A. Differential Analysis
- B. Chi squared analysis
- C. Raw Quick Pair
- D. Discrete Cosine Transform
Answer: C
Explanation:
Raw Quick Pair
https://www.cs.auckland.ac.nz/courses/compsci725s2c/archive/termpapers/yy.pdf Du and Long2 (2000) introduced Raw Quick Pairs detecting method of Stego-images (the images that contain the steganographic message). The underlying principle of the method is that the number of close color pairs of Stego-images will be larger compare with the number of close color pairs of normal images. In contrast, Fridrich and Goljan (2001) pointed out that RQP method only works if the number of unique colors is relatively low; and the method can not be applied to grayscale images. However, this paper will outline the core principle of RQP method; and evaluate such critical comments in details. In addition, this paper suggests potential improvement of RQP method and provides one possible alternative.
Incorrect answers:
Chi squared analysis - https://en.wikipedia.org/wiki/Chi-squared_test
Differential Analysis - https://en.wikipedia.org/wiki/Differential_cryptanalysis Discrete Cosine Transform - https://en.wikipedia.org/wiki/Discrete_cosine_transform
NEW QUESTION 37
Which of the following was a multi alphabet cipher widely used from the 16th century to the early 20th century?
- A. Scytale
- B. Atbash
- C. Vigenere
- D. Caesar
Answer: C
Explanation:
Vigenere
https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher
The Vigenere cipher is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword. It employs a form of polyalphabetic substitution.
First described by Giovan Battista Bellaso in 1553, the cipher is easy to understand and implement, but it resisted all attempts to break it until 1863, three centuries later. This earned it the description le chiffre indechiffrable (French for 'the indecipherable cipher'). Many people have tried to implement encryption schemes that are essentially Vigenere ciphers. In 1863, Friedrich Kasiski was the first to publish a general method of deciphering Vigenere ciphers.
Incorrect answers:
Caesar - Monoalphabetic cipher where letters are shifted one or more letters in either direction. The method is named after Julius Caesar, who used it in his private correspondence.
Atbash - Single substitution monoalphabetic cipher that substitutes each letter with its reverse (a and z, b and y, etc).
Scytale - Transposition cipher. A staff with papyrus or letter wrapped around it so edges would line up. There would be a stream of characters which would show you your message. When unwound it would be a random string of characters. Would need an identical size staff on other end for other individuals to decode message.
NEW QUESTION 38
A ______ refers to a situation where two different inputs yield the same output.
- A. Convergence
- B. Transposition
- C. Collision
- D. Substitution
Answer: C
Explanation:
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 39
Ciphers that write message letters out diagonally over a number of rows then read off cipher row by row. Also called zig-zag cipher.
- A. ROT-13
- B. Vigenere Cipher
- C. Null Cipher
- D. Rail Fence Cipher
Answer: D
Explanation:
Rail Fence Cipher
https://en.wikipedia.org/wiki/Rail_fence_cipher
The rail fence cipher (also called a zigzag cipher) is a form of transposition cipher. It derives its name from the way in which it is encoded.
Incorrect answers:
Null cipher - also known as concealment cipher, is an ancient form of encryption where the plaintext is mixed with a large amount of non-cipher material. Today it is regarded as a simple form of steganography, which can be used to hide ciphertext.
Vigenere cipher - is a method of encrypting alphabetic text by using a series of interwoven Caesar ciphers, based on the letters of a keyword. It employs a form of polyalphabetic substitution.
ROT13 - ("rotate by 13 places", sometimes hyphenated ROT-13) is a simple letter substitution cipher that replaces a letter with the 13th letter after it, in the alphabet. ROT13 is a special case of the Caesar cipher which was developed in ancient Rome.
NEW QUESTION 40
Juanita is attempting to hide some text into a jpeg file. Hiding messages inside another medium is referred to as which one of the following?
- A. Cryptology
- B. Cryptography
- C. Steganography
- D. Steganalysis
Answer: C
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 word steganography comes from Greek steganographia, which combines the words steganos, meaning "covered or concealed", and -graphia meaning "writing".
Incorrect answers:
Cryptography, or cryptology, is the practice and study of techniques for secure communication in the presence of third parties called adversaries.
Steganalysis - is the study of detecting messages hidden using steganography; this is analogous to cryptanalysis applied to cryptography.
NEW QUESTION 41
The next number is derived from adding together the prior two numbers (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89).
- A. Fibonacci Sequence
- B. Fermat pseudoprime
- C. Prime numbers
- D. Odd numbers
Answer: A
Explanation:
Fibonacci Sequence
https://en.wikipedia.org/wiki/Fibonacci_number
In mathematics, the Fibonacci numbers, commonly denoted Fn, form a sequence, called the Fibonacci sequence, such that each number is the sum of the two preceding ones, starting from 0 and 1. That is, F0 = 0, F1=1, Fn = Fn-1 + Fn-2; for n > 1.
The beginning of the sequence is thus:
0,1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144...
Incorrect answers:
Prime numbers - numbers that have only 2 factors: 1 and themselves. 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47...
Fermat numbers - a positive integer of the form Fn = 2^2^n +1; where n is a non-negative integer. The first few Fermat numbers are: 3, 5, 17, 257, 65537, 4294967297, 18446744073709551617, ...
Odd numbers - any number which cannot be divided by two 1, 3, 5, 7, 9, 11, 13, 15 ...
NEW QUESTION 42
This algorithm was published by the German engineering firm Seimans in 1993. It is a software based stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking generator ciphers.
- A. Twofish
- B. FISH
- C. Blowfish
- D. RC4
Answer: B
Explanation:
FISH
https://en.wikipedia.org/wiki/FISH_(cipher)
The FISH (FIbonacci SHrinking) stream cipher is a fast software based stream cipher using Lagged Fibonacci generators, plus a concept from the shrinking generator cipher. It was published by Siemens in 1993. FISH is quite fast in software and has a huge key length. However, in the same paper where he proposed Pike, Ross Anderson showed that FISH can be broken with just a few thousand bits of known plaintext.
NEW QUESTION 43
Which of the following uses an 80 bit key on 64 bit blocks?
- A. DES
- B. AES
- C. Twofish
- D. Skipjack
Answer: D
Explanation:
Skipjack
https://en.wikipedia.org/wiki/Skipjack_(cipher)
Skipjack uses an 80-bit key to encrypt or decrypt 64-bit data blocks. It is an unbalanced Feistel network with 32 rounds.
Incorrect answers:
Twofish - is a symmetric key block cipher with a block size of 128 bits and key sizes up to 256 bits. It was one of the five finalists of the Advanced Encryption Standard contest, but it was not selected for standardization. Twofish is related to the earlier block cipher Blowfish.
AES - 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.
DES - 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 44
A cryptographic hash function which uses a Merkle tree-like structure to allow for immense parallel computation of hashes for very long inputs. Authors claim a performance of 28 cycles per byte for MD6-256 on an Intel Core 2 Duo and provable resistance against differential cryptanalysis.
- A. MD6
- B. TIGER
- C. MD5
- D. GOST
Answer: A
Explanation:
MD6
https://en.wikipedia.org/wiki/MD6
The MD6 Message-Digest Algorithm is a cryptographic hash function. It uses a Merkle tree-like structure to allow for immense parallel computation of hashes for very long inputs. Authors claim a performance of 28 cycles per byte for MD6-256 on an Intel Core 2 Duo and provable resistance against differential cryptanalysis.[2] The source code of the reference implementation was released under MIT license.
Speeds in excess of 1 GB/s have been reported to be possible for long messages on 16-core CPU architecture.
In December 2008, Douglas Held of Fortify Software discovered a buffer overflow in the original MD6 hash algorithm's reference implementation. This error was later made public by Ron Rivest on 19 February 2009, with a release of a corrected reference implementation in advance of the Fortify Report.
NEW QUESTION 45
If you use substitution alone, what weakness is present in the resulting cipher text?
- A. It maintains letter and word frequency
- B. It is easily broken with modern computers
- C. It is too simple
- D. It is the same length as the original text
Answer: A
Explanation:
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.
NEW QUESTION 46
What is a salt?
- A. Key rotation
- B. Random bits intermixed with a symmetric cipher to increase randomness and make it more secure
- C. Random bits intermixed with a hash to increase randomness and reduce collisions
- D. Key whitening
Answer: C
Explanation:
Random bits intermixed with a hash to increase randomness and reduce collisions
https://en.wikipedia.org/wiki/Salt_(cryptography)
Salt is random data that is used as an additional input to a one-way function that hashes data, a password or passphrase. Salts are used to safeguard passwords in storage. Historically a password was stored in plaintext on a system, but over time additional safeguards were developed to protect a user's password against being read from the system. A salt is one of those methods.
Incorrect answers:
Key whitening - 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.
Key rotation - is when you retire an encryption key and replace that old key by generating a new cryptographic key. Rotating keys on a regular basis help meet industry standards and cryptographic best practices.
Random bits intermixed with a symmetric cipher to increase randomness and make it more secure - Initialization Vector (IV)
NEW QUESTION 47
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 48
Which of the following is a block cipher?
- A. RSA
- B. AES
- C. DH
- D. RC4
Answer: B
Explanation:
AES
https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
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 Incorrect answers:
RC4. RC4 (Rivest Cipher 4 also known as ARC4 or ARCFOUR meaning Alleged RC4, see below) is a stream 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.
RSA. RSA (Rivest-Shamir-Adleman) is one of the first public-key cryptosystems and is widely used for secure data transmission.
NEW QUESTION 49
The concept that if one bit of data changes, the cipher text will all completely change as well.
- A. Confusion
- B. Collision
- C. Substitution
- D. Avalanche
Answer: D
Explanation:
Avalanche
https://en.wikipedia.org/wiki/Avalanche_effect
In cryptography, the avalanche effect is 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. The actual term was first used by Horst Feistel, although the concept dates back to at least Shannon's diffusion.
Incorrect answers:
Confusion - Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key, obscuring the connections between the two.
The property of confusion hides the relationship between the ciphertext and the key.
This property makes it difficult to find the key from the ciphertext and if a single bit in a key is changed, the calculation of the values of most or all of the bits in the ciphertext will be affected.
Confusion increases the ambiguity of ciphertext and it is used by both block and stream ciphers.
Substitution - method of encrypting by which units of plaintext are replaced with ciphertext, according to a fixed system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing the inverse substitution.
Collision - occurs when a hash function generates the same output for different inputs.
NEW QUESTION 50
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