2023 Valid 212-81 Real Exam Questions, practice ECES
Latest Success Metrics For Actual 212-81 Exam (Updated 200 Questions)
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NEW QUESTION 44
In steganography, ________ is the data to be covertly communicated (in other words, it is the message you wish to hide).
- A. Signal
- B. Carrier
- C. Payload
- D. Channel
Answer: C
Explanation:
Payload
https://en.wikipedia.org/wiki/Steganography
The payload is the data covertly communicated. The carrier is the signal, stream, or data file that hides the payload, which differs from the channel, which typically means the type of input, such as a JPEG image. The resulting signal, stream, or data file with the encoded payload is sometimes called the package, stego file, or covert message. The proportion of bytes, samples, or other signal elements modified to encode the payload is called the encoding density and is typically expressed as a number between 0 and 1.
NEW QUESTION 45
What is a "Collision attack" in cryptography?
- A. Collision attacks try to break the hash into two parts, with the same bytes in each part to get the private key
- B. Collision attacks try to get the public key
- C. Collision attacks try to break the hash into three parts to get the plaintext value
- D. Collision attacks try to find two inputs producing the same
Answer: D
Explanation:
Collision attacks try to find two inputs producing the same
https://en.wikipedia.org/wiki/Collision_attack
A collision attack on a cryptographic hash tries to find two inputs producing the same hash value, i.e. a hash collision. This is in contrast to a preimage attack where a specific target hash value is specified.
NEW QUESTION 46
You are studying classic ciphers. You have been examining the difference between single substitution and multi-substitution. Which one of the following is an example of a multi-alphabet cipher?
- A. Caesar
- B. Rot13
- C. Atbash
- D. Vigenere
Answer: D
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.
NEW QUESTION 47
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. SHA-1
- C. Keccak
- 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 48
A _______ product refers to an NSA-endorsed classified or controlled cryptographic item for classified or sensitive U. S. government information, including cryptographic equipment, assembly, or component classified or certified by NSA for encrypting and decrypting classified and sensitive national security information when appropriately keyed
- A. Type 3
- B. Type 1
- C. Type 2
- D. Type 4
Answer: B
Explanation:
Type 1
https://en.wikipedia.org/wiki/NSA_cryptography#Type_1_Product
A Type 1 Product refers to an NSA endorsed classified or controlled cryptographic item for classified or sensitive U.S. government information, including cryptographic equipment, assembly or component classified or certified by NSA for encrypting and decrypting classified and sensitive national security information when appropriately keyed.
Incorrect answers:
Type 2 - product refers to an NSA endorsed unclassified cryptographic equipment, assemblies or components for sensitive but unclassified U.S. government information.
Type 3 - unclassified cryptographic equipment, assembly, or component used, when appropriately keyed, for encrypting or decrypting unclassified sensitive U.S. Government or commercial information, and to protect systems requiring protection mechanisms consistent with standard commercial practices. A Type 3 Algorithm refers to NIST endorsed algorithms, registered and FIPS published, for sensitive but unclassified U.S. government and commercial information.
Type 4 - Algorithm refers to algorithms that are registered by the NIST but are not FIPS published. Unevaluated commercial cryptographic equipment, assemblies, or components that are neither NSA nor NIST certified for any Government usage.
NEW QUESTION 49
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. Raw Quick Pair
- C. Discrete Cosine Transform
- D. Chi squared analysis
Answer: B
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 50
Which of the following statements is most true regarding binary operations and encryption?
- A. They can provide secure encryption
- B. They are completely useless
- C. They are only useful as a teaching method
- D. They can form a part of viable encryption methods
Answer: D
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 51
What best describes the shifting of each letter a fixed number of spaces to the left or right?
- A. XOR
- B. Bit shifting
- C. Single substitution
- D. Multi substitution
Answer: C
Explanation:
Single substitution
https://en.wikipedia.org/wiki/Substitution_cipher#Simple_substitution
Substitution of single letters separately-simple substitution-can be demonstrated by writing out the alphabet in some order to represent the substitution. This is termed a substitution alphabet. The cipher alphabet may be shifted or reversed (creating the Caesar and Atbash ciphers, respectively) or scrambled in a more complex fashion, in which case it is called a mixed alphabet or deranged alphabet.
NEW QUESTION 52
Which of the following is an asymmetric cipher?
- A. RSA
- B. RC4
- C. DES
- D. AES
Answer: A
Explanation:
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.
Incorrect answers:
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.
RC4 - RSA (Rivest-Shamir-Adleman) is one of the first public-key cryptosystems and is widely used for secure data transmission (stream cipher).
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.
NEW QUESTION 53
Terrance oversees the key escrow server for his company. All employees use asymmetric cryptography to encrypt all emails. How many keys are needed for asymmetric cryptography?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: D
Explanation:
:
2
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.
NEW QUESTION 54
What is the name of the attack where the attacker obtains the ciphertexts corresponding to a set of plaintexts of his own choosing?
- A. Chosen plaintext
- B. Kasiski examination
- C. Differential cryptanalysis
- D. Known-plaintext attack
Answer: A
Explanation:
Chosen plaintext
https://en.wikipedia.org/wiki/Chosen-plaintext_attack
A chosen-plaintext attack (CPA) is an attack model for cryptanalysis which presumes that the attacker can obtain the ciphertexts for arbitrary plaintexts. The goal of the attack is to gain information that reduces the security of the encryption scheme.
Incorrect answers:
Differential cryptanalysis - is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. In the broadest sense, it is the study of how differences in information input can affect the resultant difference at the output. In the case of a block cipher, it refers to a set of techniques for tracing differences through the network of transformation, discovering where the cipher exhibits non-random behavior, and exploiting such properties to recover the secret key (cryptography key).
Known-plaintext attack - (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secret keys and code books.
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. In polyalphabetic substitution ciphers where the substitution alphabets are chosen by the use of a keyword, the Kasiski examination allows a cryptanalyst to deduce the length of the keyword. Once the length of the keyword is discovered, the cryptanalyst lines up the ciphertext in n columns, where n is the length of the keyword. Then each column can be treated as the ciphertext of a monoalphabetic substitution cipher. As such, each column can be attacked with frequency analysis.
NEW QUESTION 55
What is the formula m^e %n related to?
- A. Encrypting with RSA
- B. Encrypting with EC
- C. Decrypting with RSA
- D. Generating Mersenne primes
Answer: A
Explanation:
Encrypting with RSA
https://en.wikipedia.org/wiki/RSA_(cryptosystem)
RSA Encrypting a message m (number) with the public key (n, e) is calculated:
M' := m^e %n
Incorrect answers:
Decrypting with RSA:
M'' := m^d %n
Generation Mersenne primes:
Mn = 2^n - 1
Encrypting with Elliptic Curve (EC):
y^2 = x^3 + ax + b
NEW QUESTION 56
Changing some part of the plain text for some matching part of cipher text. Historical algorithms typically use this.
- A. Substitution
- B. Collision
- C. Transposition
- D. Decoding
Answer: A
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 57
Which of the following uses an 80 bit key on 64 bit blocks?
- A. Twofish
- B. DES
- C. AES
- 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 58
Basic information theory is the basis for modern symmetric ciphers. Understanding the terminology of information theory is, therefore, important. Changes to one character in the plaintext affect multiple characters in the ciphertext. What is this referred to?
- A. Avalanche
- B. Scrambling
- C. Confusion
- D. Diffusion
Answer: D
Explanation:
Diffusion
https://en.wikipedia.org/wiki/Confusion_and_diffusion
Diffusion means that if we change a single bit of the plaintext, then (statistically) half of the bits in the ciphertext should change, and similarly, if we change one bit of the ciphertext, then approximately one half of the plaintext bits should change. Since a bit can have only two states, when they are all re-evaluated and changed from one seemingly random position to another, half of the bits will have changed state.
The idea of diffusion is to hide the relationship between the ciphertext and the plain text.
This will make it hard for an attacker who tries to find out the plain text and it increases the redundancy of plain text by spreading it across the rows and columns; it is achieved through transposition of algorithm and it is used by block ciphers only 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.
Avalanche https://en.wikipedia.org/wiki/Avalanche_effect
An 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.
If a block cipher or cryptographic hash function does not exhibit the avalanche effect to a significant degree, then it has poor randomization, and thus a cryptanalyst can make predictions about the input, being given only the output. This may be sufficient to partially or completely break the algorithm. Thus, the avalanche effect is a desirable condition from the point of view of the designer of the cryptographic algorithm or device.
Constructing a cipher or hash to exhibit a substantial avalanche effect is one of the primary design objectives, and mathematically the construction takes advantage of the butterfly effect. This is why most block ciphers are product ciphers. It is also why hash functions have large data blocks. Both of these features allow small changes to propagate rapidly through iterations of the algorithm, such that every bit of the output should depend on every bit of the input before the algorithm terminates.
NEW QUESTION 59
A list of certificates that have been revoked.
- A. OCSP
- B. CA
- C. CRL
- D. PCBC
Answer: C
Explanation:
CRL
https://en.wikipedia.org/wiki/Certificate_revocation_list
In cryptography, a 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:
PCBC - the propagating cipher block chaining or plaintext cipher-block chaining mode was designed to cause small changes in the ciphertext to propagate indefinitely when decrypting, as well as when encrypting. In PCBC mode, each block of plaintext is XORed with both the previous plaintext block and the previous ciphertext block before being encrypted. As with CBC mode, an initialization vector is used in the first block.
CA - certificate authority or certification authority is an entity that issues digital certificates.
OCSP - 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).
NEW QUESTION 60
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