Latest Success Metrics For Actual 212-81 Exam (Updated 200 Questions)
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NEW QUESTION 31
Represents the total number of possible values of keys in a cryptographic algorithm or other security measure, such as a password.
- A. Key Exchange
- B. Key Schedule
- C. Key Space
- D. Key Clustering
Answer: C
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 32
Which of the following asymmetric algorithms is described by U.S. Patent 5,231,668 and FIPS 186
- A. RSA
- B. DSA
- C. AES
- D. RC4
Answer: B
Explanation:
DSA
https://ru.wikipedia.org/wiki/DSA
The National Institute of Standards and Technology (NIST) proposed DSA for use in their Digital Signature Standard (DSS) in 1991, and adopted it as FIPS 186 in 1994.
DSA is covered by U.S. Patent 5,231,668 , filed July 26, 1991 and now expired, and attributed to David W. Kravitz, a former NSA employee.
NEW QUESTION 33
Storing private keys with a third party is referred to as what?
- A. Key banking
- B. Key caching
- C. Key storage
- D. Key escrow
Answer: D
Explanation:
Key escrow
https://en.wikipedia.org/wiki/Key_escrow
Key escrow (also known as a "fair" cryptosystem) is an arrangement in which the keys needed to decrypt encrypted data are held in escrow so that, under certain circumstances, an authorized third party may gain access to those keys. These third parties may include businesses, who may want access to employees' secure business-related communications, or governments, who may wish to be able to view the contents of encrypted communications (also known as exceptional access).
NEW QUESTION 34
Which of the following statements is most true regarding binary operations and encryption?
- A. They are only useful as a teaching method
- B. They can form a part of viable encryption methods
- C. They are completely useless
- D. They can provide secure encryption
Answer: B
Explanation:
They can form a part of viable encryption methods
for example - https://en.wikipedia.org/wiki/XOR_cipher
The XOR operator is extremely common as a component in more complex ciphers. By itself, using a constant repeating key, a simple XOR cipher can trivially be broken using frequency analysis. If the content of any message can be guessed or otherwise known then the key can be revealed. Its primary merit is that it is simple to implement, and that the XOR operation is computationally inexpensive. A simple repeating XOR (i.e. using the same key for xor operation on the whole data) cipher is therefore sometimes used for hiding information in cases where no particular security is required. The XOR cipher is often used in computer malware to make reverse engineering more difficult.
NEW QUESTION 35
The reverse process from encoding - converting the encoded message back into its plaintext format.
- A. Substitution
- B. Whitening
- C. Encoding
- D. Decoding
Answer: D
Explanation:
Decoding
Decoding - reverse process from encoding,converting the encoded message back into its plaintext format.
NEW QUESTION 36
____________cryptography uses one key to encrypt a message and a different key to decrypt it.
- A. Asymmetric
- B. Symmetric
- C. Stream
- D. Secure
Answer: A
Explanation:
Asymmetric
https://en.wikipedia.org/wiki/Public-key_cryptography
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.
NEW QUESTION 37
Changing some part of the plain text for some matching part of cipher text. Historical algorithms typically use this.
- A. Transposition
- B. Substitution
- C. Collision
- D. Decoding
Answer: B
Explanation:
Substitution
https://en.wikipedia.org/wiki/Substitution_cipher
In cryptography, a substitution cipher is a 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.
Incorrect answers:
Decoding - the reverse process from encoding - converting the encoded message back into its plaintext format.
Collision - occurs when a hash function generates the same output for different inputs.
Transposition - a method of encryption by which the positions held by units of plaintext (which are commonly characters or groups of characters) are shifted according to a regular system, so that the ciphertext constitutes a permutation of the plaintext. That is, the order of the units is changed (the plaintext is reordered). Mathematically a bijective function is used on the characters' positions to encrypt and an inverse function to decrypt.
NEW QUESTION 38
The next number is derived from adding together the prior two numbers (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89).
- A. Fermat pseudoprime
- B. Odd numbers
- C. Prime numbers
- D. Fibonacci Sequence
Answer: D
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 39
During the process of encryption and decryption, what keys are shared?
- A. Public keys
- B. Private keys
- C. User passwords
- D. Public and private keys
Answer: A
Explanation:
Public keys
https://en.wikipedia.org/wiki/Public-key_cryptography
Public-key cryptography, or asymmetric cryptography, is a cryptographic system that uses pairs of keys: public keys, which may be disseminated widely, and private keys, which are known only to the owner. The generation of such keys depends on cryptographic algorithms based on mathematical problems to produce one-way functions. Effective security only requires keeping the private key private; the public key can be openly distributed without compromising security.
In such a system, any person can encrypt a message using the receiver's public key, but that encrypted message can only be decrypted with the receiver's private key.
Alice and Bob have two keys of their own - just to be clear, that's four keys total. Each party has their own public key, which they share with the world, and their own private key which they well, which they keep private, of course but, more than that, which they keep as a closely guarded secret. The magic of public key cryptography is that a message encrypted with the public key can only be decrypted with the private key. Alice will encrypt her message with Bob's public key, and even though Eve knows she used Bob's public key, and even though Eve knows Bob's public key herself, she is unable to decrypt the message. Only Bob, using his secret key, can decrypt the message assuming he's kept it secret, of course.
Alice and Bob do not need to plan anything ahead of time to communicate securely: they generate their public-private key pairs independently, and happily broadcast their public keys to the world at large. Alice can rest assured that only Bob can decrypt the message she sends because she has encrypted it with his public key.
NEW QUESTION 40
What is the basis for the FISH algorithm?
- A. The difficulty in factoring numbers
- B. Prime number theory
- C. The Lagged Fibonacci generator
- D. Equations that describe an ellipse
Answer: C
Explanation:
The Lagged Fibonacci generator
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 41
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 the same length as the original text
- D. It is too simple
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 42
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. MD5
- B. Keccak
- C. SHA-1
- D. TIGER
Answer: A
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 43
Which one of the following attempts to hide data in plain view?
- A. Cryptography
- B. Substitution
- C. Steganography
- D. Asymmetric cryptography
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".
NEW QUESTION 44
Which of the following acts as a verifier for the certificate authority?
- A. Certificate authority
- B. Directory management system
- C. Registration authority
- D. Certificate Management system
Answer: C
Explanation:
Registration authority
https://en.wikipedia.org/wiki/Registration_authority
Registration authorities exist for many standards organizations, such as ANNA (Association of National Numbering Agencies for ISIN), the Object Management Group, W3C, IEEE and others. In general, registration authorities all perform a similar function, in promoting the use of a particular standard through facilitating its use. This may be by applying the standard, where appropriate, or by verifying that a particular application satisfies the standard's tenants. Maintenance agencies, in contrast, may change an element in a standard based on set rules - such as the creation or change of a currency code when a currency is created or revalued (i.e. TRL to TRY for Turkish lira). The Object Management Group has an additional concept of certified provider, which is deemed an entity permitted to perform some functions on behalf of the registration authority, under specific processes and procedures documented within the standard for such a role.
NEW QUESTION 45
Which of the following is a cryptographic protocol that allows two parties to establish a shared key over an insecure channel?
- A. RSA
- B. NMD5
- C. Diffie-Hellman
- D. Elliptic Curve
Answer: C
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 46
Which of the following areas is considered a strength of symmetric key cryptography when compared with asymmetric algorithms?
- A. Scalability
- B. Security
- C. Key distribution
- D. Speed
Answer: D
Explanation:
Speed
Symmetric key systems are considerably faster than asymmetric key systems but have issues with proper key distribution, controlling keys as more users need to communicate, and cannot provide non-repudiation or authenticity.
NEW QUESTION 47
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