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A message is authentic and digitally signed if sent with:
A.
A message digest/hash encrypted with the sender’s private key
B.
A message digest/hash encrypted with the sender’s public key
C.
A message digest/hash encrypted with the receiver’s private key
D.
A message digest/hash encrypted with the receiver’s private key
Correct Answer A. A message digest/hash encrypted with the sender’s private key
Explanation When a message is authentic and digitally signed, it means that the sender's identity is verified and the message has not been tampered with during transmission. In this case, the correct answer is "A message digest/hash encrypted with the sender’s private key." This is because the sender uses their private key to encrypt the message digest or hash of the message. The recipient can then use the sender's public key to decrypt the message digest and verify its authenticity. By using the private key for encryption, only the sender with the corresponding private key can create the digital signature, ensuring the integrity and authenticity of the message.
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2.
Heart of Data Encryption Standard (DES), is the
A.
Cipher
B.
Rounds
C.
Encryption
D.
DES function
Correct Answer D. DES function
Explanation The correct answer is DES function. The DES function is the core component of the Data Encryption Standard (DES) algorithm. It is responsible for performing the encryption and decryption operations on the input data. The DES function consists of several rounds of complex mathematical operations, including permutation, substitution, and exclusive OR (XOR) operations. These operations ensure the security and confidentiality of the data by transforming it into an encrypted form that can only be decrypted with the correct key.
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3.
Digital Signatures are:
A.
Proof of authenticity of the sender
B.
Proof of authenticity of the receiver
C.
Proof of authenticity of the verifier
D.
Proof of authenticity of Alice
Correct Answer A. Proof of authenticity of the sender
Explanation Digital signatures are a cryptographic technique used to verify the authenticity of the sender of a message or document. They provide proof that the sender is who they claim to be and that the message has not been tampered with during transmission. By using a private key to encrypt the message, the sender creates a unique digital signature that can only be decrypted with their public key. This allows the receiver to verify the sender's identity and ensure the integrity of the message. Therefore, the correct answer is "Proof of authenticity of the sender."
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4.
In symmetric-key cryptography, the key used by sender and receiver is
A.
Shared
B.
Different
C.
Two keys are used
D.
None
Correct Answer A. Shared
Explanation In symmetric-key cryptography, the key used by the sender and receiver is "shared." This means that both parties have access to the same key, which is used for both encryption and decryption of the message. By sharing the key, the sender can encrypt the message using the key, and the receiver can decrypt it using the same key. This ensures that only the intended recipient, who possesses the key, can decrypt and access the message.
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5.
In symmetric key cryptography, key(s) used for encryption and decryption is/are
A.
Same
B.
Different
C.
Private
D.
Public
Correct Answer A. Same
Explanation In symmetric key cryptography, the key used for encryption and decryption is the same key. This means that both the sender and the receiver use the same secret key to both encrypt and decrypt the message. This is in contrast to asymmetric key cryptography, where there are separate public and private keys for encryption and decryption.
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6.
Keys used in cryptography are:
A.
Secret key
B.
Private key
C.
Public key
D.
All of them
E.
None of them
Correct Answer D. All of them
Explanation Keys used in cryptography include a secret key, a private key, and a public key. A secret key is used in symmetric encryption algorithms where the same key is used for both encryption and decryption. A private key is used in asymmetric encryption algorithms where a different key is used for encryption and decryption. A public key is used in asymmetric encryption algorithms where the public key is used for encryption and the corresponding private key is used for decryption. Therefore, all three types of keys are used in cryptography.
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7.
Cryptography can provide:
A.
All of them
B.
Entity authentication
C.
Nonrepudiation of messages
D.
Confidentiality
Correct Answer A. All of them
Explanation Cryptography is a powerful tool that can provide various security features. Entity authentication ensures that the communicating parties can verify each other's identities, preventing unauthorized access. Nonrepudiation of messages ensures that the sender cannot deny sending a message, providing accountability. Confidentiality ensures that the information exchanged between parties remains private and cannot be accessed by unauthorized individuals. Therefore, cryptography can indeed provide all of these security features.
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8.
Advanced Encryption Standard (AES), has three different configurations with respect to number of rounds and
A.
Key Size
B.
Datasize
C.
Round Size
D.
Encryption Size
Correct Answer A. Key Size
Explanation The given question is incomplete as it does not provide any specific information or options to choose from. Therefore, an explanation cannot be generated.
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9.
Cryptography algorithms (ciphers) are divided into:
A.
Two groups.
B.
Four groups.
C.
One single group
D.
None
Correct Answer A. Two groups.
Explanation Cryptography algorithms (ciphers) are divided into two groups. This means that there are two distinct categories or classifications for these algorithms. This division allows for easier organization and understanding of the different types of ciphers. It also suggests that there are different characteristics or properties that differentiate the algorithms within each group.
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10.
In cryptography, original message, before being transformed, is called
A.
Simple text
B.
Plain text
C.
Empty text
D.
Filled text
Correct Answer B. Plain text
Explanation In cryptography, the original message that is yet to be encrypted or transformed is referred to as the plain text. This term is used to distinguish the unencrypted message from the encrypted or transformed version. It is the message in its original form before any encryption or cryptographic operations are applied to it.
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11.
A hash function guarantees integrity of a message. It guarantees that message has not be
A.
Replaced
B.
Over view
C.
Changed
D.
Left
Correct Answer C. Changed
Explanation A hash function guarantees the integrity of a message by generating a unique hash value for a given message. This hash value acts as a digital fingerprint for the message, ensuring that any changes made to the message will result in a different hash value. Therefore, if the hash value of a message is different from the original hash value, it indicates that the message has been changed in some way.
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12.
Message digest is referred to:
A.
RSA
B.
Digital signature
C.
Hash function
D.
Digital signature with hash function
Correct Answer C. Hash function
Explanation A message digest is a fixed-size numerical value that is generated by applying a hash function to a message. It is used to ensure the integrity and authenticity of the message by providing a unique identifier for the message. Unlike RSA, which is a public-key encryption algorithm, a message digest does not involve encryption or decryption. It is also different from a digital signature, which involves the use of a private key to sign a message. Therefore, the correct answer is "Hash function."
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13.
SHA means:
A.
Secret Hash Algorithm
B.
Secure Hash Algorithm
C.
Sneaky Hash Algorithm
D.
Super Hash Algorithm
Correct Answer B. Secure Hash Algorithm
Explanation The correct answer is "Secure Hash Algorithm." SHA stands for Secure Hash Algorithm, which is a cryptographic hash function used to generate unique hash values for data. It is widely used in various security applications, such as digital signatures, password storage, and data integrity verification.
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14.
Number of submissions for SHA-3 algorithm:
A.
15
B.
64
C.
128
D.
45
Correct Answer B. 64
Explanation The correct answer is 64. This suggests that there were 64 submissions for the SHA-3 algorithm.
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15.
SHA-1 has a message digest of :
A.
160 bits
B.
512 bits
C.
628 bits
D.
820 bits
Correct Answer A. 160 bits
Explanation SHA-1 is a cryptographic hash function that produces a fixed-size output of 160 bits. This means that regardless of the size of the input message, the SHA-1 algorithm will always generate a 160-bit message digest. The purpose of the message digest is to provide a unique representation of the input message, ensuring data integrity and allowing for efficient verification. The 160-bit size of the SHA-1 message digest provides a good balance between security and efficiency in many applications.
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16.
To check integrity of a message or document, receiver creates the :
A.
Cipher text
B.
Hash
C.
Hyper Text
D.
Finger Print
Correct Answer B. Hash
Explanation To check the integrity of a message or document, the receiver creates a hash. A hash is a fixed-length string of characters that is generated by applying a mathematical algorithm to the content of the message or document. This hash serves as a unique identifier for the content, allowing the receiver to compare it with the original hash provided by the sender. If the hashes match, it ensures that the message or document has not been tampered with during transmission.
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17.
A digital signature needs a:
A.
Private key
B.
Shared key
C.
Public key
D.
Both A and C
E.
None of them
Correct Answer D. Both A and C
Explanation A private key is used to create the digital signature, and a public key is used to verify the signature. The private key is kept secret and should only be known to the owner, while the public key is shared with others who need to verify the digital signatures created with the corresponding private key. There is no shared key involved in the process of creating or verifying digital signatures.
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18.
Symmetric encryption:
A.
Used to conceal the contents of block or stream of data of any size, including messages, files, encryption keys, and passwords
B.
Used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures
C.
Used to protect blocks of data, such as messages, from alteration
D.
These are schemes based on the use of cryptographic algorithms designed to authenticate the identity of entities
Correct Answer A. Used to conceal the contents of block or stream of data of any size, including messages, files, encryption keys, and passwords
Explanation Symmetric encryption is a cryptographic technique that is used to hide the contents of a block or stream of data, regardless of its size. It can be applied to conceal various types of information, such as messages, files, encryption keys, and passwords. This encryption method ensures that the data remains confidential and secure from unauthorized access. By using symmetric encryption, the data is transformed into an unreadable format, making it unintelligible to anyone without the proper decryption key. This ensures the privacy and integrity of the data being transmitted or stored.
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19.
Asymmetric encryption:
A.
Used to conceal the contents of block or stream of data of any size, including messages, files, encryption keys, and passwords
B.
Used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures
C.
Used to protect blocks of data, such as messages, from alteration
D.
These are schemes based on the use of cryptographic algorithms designed to authenticate the identity of entities
Correct Answer B. Used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures
Explanation Asymmetric encryption is used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures. This type of encryption involves the use of a pair of keys, a public key for encryption and a private key for decryption. The public key can be freely shared, allowing anyone to encrypt data, while the private key is kept secret and used to decrypt the data. By using asymmetric encryption, the integrity and authenticity of the small blocks of data, such as encryption keys and hash function values, can be ensured in digital signatures.
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20.
Authentication protocol:
A.
Used to conceal the contents of block or stream of data of any size, including messages, files, encryption keys, and passwords
B.
Used to conceal small blocks of data, such as encryption keys and hash function values, which are used in digital signatures
C.
Used to protect blocks of data, such as messages, from alteration
D.
These are schemes based on the use of cryptographic algorithms designed to authenticate the identity of entities
Correct Answer D. These are schemes based on the use of cryptographic algorithms designed to authenticate the identity of entities
Explanation The given answer accurately describes the purpose of an authentication protocol. Authentication protocols are used to verify and confirm the identity of entities, such as users or devices, in a secure manner. These protocols rely on cryptographic algorithms to ensure that the identity being claimed is legitimate and not falsified. By using encryption and other security measures, authentication protocols protect against unauthorized access and impersonation.
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21.
What is Computer Security
A.
Protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability, and confidentiality of information system resources
B.
Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information.
C.
Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity.
D.
Ensuring timely and reliable access to and use of information.
Correct Answer A. Protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability, and confidentiality of information system resources
Explanation Computer security refers to the measures taken to protect an automated information system. These measures aim to achieve the objectives of maintaining the integrity, availability, and confidentiality of the resources within the information system. This includes safeguarding against unauthorized access and disclosure of information, protecting personal privacy and proprietary information, preventing improper modification or destruction of information, and ensuring reliable and timely access to and use of information.
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22.
What is Confidentiality?
A.
Protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability, and confidentiality of information system resources
B.
Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information.
C.
Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity.
D.
Ensuring timely and reliable access to and use of information.
Correct Answer B. Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information.
Explanation Confidentiality refers to the preservation of authorized restrictions on information access and disclosure, which includes measures to protect personal privacy and proprietary information. This means that only those who are authorized should have access to certain information, and it should not be disclosed to unauthorized individuals. This helps to maintain the privacy and security of personal and sensitive information, preventing it from falling into the wrong hands.
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23.
What is Integrity?
A.
Protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability, and confidentiality of information system resources
B.
Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information.
C.
Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity.
D.
Ensuring timely and reliable access to and use of information.
Correct Answer C. Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity.
Explanation Integrity refers to the protection against improper information modification or destruction. It involves ensuring that information cannot be tampered with or destroyed in an unauthorized manner. Additionally, integrity also includes measures to ensure information nonrepudiation and authenticity, meaning that the information can be trusted and its origin or sender cannot be denied.
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24.
What is Availability?
A.
Protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, availability, and confidentiality of information system resources
B.
Preserving authorized restrictions on information access and disclosure, including means for protecting personal privacy and proprietary information.
C.
Guarding against improper information modification or destruction, including ensuring information nonrepudiation and authenticity.
D.
Ensuring timely and reliable access to and use of information.
Correct Answer D. Ensuring timely and reliable access to and use of information.
Explanation Availability refers to the protection and assurance of timely and reliable access to information. This means that the information system is accessible and usable whenever needed, without any disruptions or delays. It involves measures to prevent unauthorized access, information modification, or destruction, and ensures that the information remains authentic and nonrepudiable. By ensuring availability, organizations can maintain the functionality and usability of their information systems, allowing users to access and utilize information as and when required.
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25.
How many rounds of processing uses DES?
A.
14
B.
15
C.
16
D.
17
Correct Answer C. 16
Explanation DES (Data Encryption Standard) is a symmetric encryption algorithm that uses a Feistel network structure. In each round of processing, DES performs several operations, including permutation, substitution, and XOR operations. Specifically, DES consists of 16 rounds of processing. During each round, the algorithm applies a different subkey derived from the original encryption key. This process increases the security and complexity of the encryption. Therefore, the correct answer is 16.
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26.
What is the encryption key size of DES
A.
8-bytes
B.
56-bit
C.
34-bit
D.
64-bit
Correct Answer B. 56-bit
Explanation The encryption key size of DES is 56-bit. DES (Data Encryption Standard) is a symmetric encryption algorithm that uses a 56-bit key to encrypt and decrypt data. The key size determines the strength of the encryption, with larger key sizes providing stronger security. In the case of DES, the 56-bit key size has been found to be vulnerable to brute-force attacks, leading to the development of more secure encryption algorithms with larger key sizes.
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27.
Diffusion
A.
Means that the relationship between the encryption key and the ciphertext must be as complex as possible
B.
Means that each plaintext bit must affect as many ciphertext bits as possible
C.
Means that each bit of the key must affect as many bits as possible
D.
Means that each row of a substitution table is indexed by the two outermost bits of a six-bit block and each column by the remaining inner 4 bit
Correct Answer B. Means that each plaintext bit must affect as many ciphertext bits as possible
Explanation Diffusion in encryption refers to the property where each plaintext bit should have an impact on as many ciphertext bits as possible. This ensures that any change in the plaintext will cause significant changes in the resulting ciphertext, making it difficult for attackers to analyze and break the encryption. By spreading the influence of each plaintext bit across multiple ciphertext bits, diffusion enhances the overall security and complexity of the encryption algorithm.
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28.
AES is
A.
3 times faster than 3DES
B.
4 times faster than 3DES
C.
5 times faster than 3DES
D.
6 times faster than 3DES
Correct Answer D. 6 times faster than 3DES
Explanation AES is six times faster than 3DES because AES (Advanced Encryption Standard) is a more efficient and faster encryption algorithm compared to 3DES (Triple Data Encryption Standard). AES uses a block size of 128 bits, while 3DES uses a block size of 64 bits. Additionally, AES employs a substitution-permutation network, which allows for faster encryption and decryption processes. The increased speed of AES makes it six times faster than 3DES in terms of encryption and decryption operations.
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29.
AES is
A.
Symmetric key encryption
B.
Assymetric key encryption
Correct Answer A. Symmetric key encryption
Explanation AES stands for Advanced Encryption Standard, which is a widely used encryption algorithm. It is a symmetric key encryption algorithm, meaning that the same key is used for both the encryption and decryption processes. In symmetric key encryption, the sender and receiver both use the same key to encrypt and decrypt the data, ensuring confidentiality and data integrity. This makes AES an efficient and secure encryption method for protecting sensitive information.
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30.
AES input data is
A.
128 bit
B.
192 bit
C.
256 bit
D.
512 bit
Correct Answer A. 128 bit
Explanation The AES (Advanced Encryption Standard) input data refers to the size of the data blocks that can be encrypted or decrypted using the AES algorithm. In this case, the correct answer is 128 bit, which means that the AES algorithm can process data blocks of 128 bits in size. This is the most commonly used block size for AES and provides a good balance between security and efficiency.
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31.
Operation in AES is based on
A.
Substitution
B.
Permutation
C.
Substitution-permutation
Correct Answer C. Substitution-permutation
Explanation The operation in AES is based on a combination of both substitution and permutation. Substitution involves replacing each byte of the input with another byte based on a specific substitution table. Permutation involves rearranging the positions of the bytes in the input. This combination of substitution and permutation provides a high level of security and makes AES resistant to various cryptographic attacks.
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32.
In AES, 192 bit key has:
A.
10 rounds
B.
12 rounds
C.
14 rounds
Correct Answer B. 12 rounds
Explanation The AES encryption algorithm with a 192-bit key size has 12 rounds. Each round consists of several operations, including substitution, permutation, and mixing of the input data. The number of rounds determines the level of security provided by the algorithm. In AES, the key size directly affects the number of rounds required for encryption. With a 192-bit key, 12 rounds are needed to ensure a strong level of security for the encrypted data.
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33.
What is the difference between stream cipher and one-time pad?
A.
Stream cipher uses truly random number stream
B.
One-time pad uses truly random number stream
C.
One-time pad uses genuine random number stream
Correct Answer C. One-time pad uses genuine random number stream
Explanation The correct answer is that one-time pad uses a genuine random number stream. This means that the numbers used in a one-time pad are truly random and not generated by any algorithm or process. In contrast, a stream cipher may use a random number stream, but it does not necessarily have to be genuinely random. It could be generated by a pseudo-random number generator, which means that it is not truly random but appears random based on a specific algorithm.
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34.
What is the difference between stream cipher and one-time pad?
A.
Stream cipher uses truly random number stream
B.
Stream cipher uses pseudo random number stream
C.
One-time pad uses truly random number stream
Correct Answer B. Stream cipher uses pseudo random number stream
Explanation The correct answer is that stream ciphers use pseudo-random number streams. This means that the numbers generated by a stream cipher are not truly random, but are instead generated using a deterministic algorithm. This algorithm takes a relatively small amount of truly random data, called a seed, and uses it to generate a much larger stream of pseudo-random numbers. This stream is then combined with the plaintext to produce the ciphertext. One-time pad, on the other hand, does use a truly random number stream, which is generated by a physical source of randomness, such as a radioactive decay or atmospheric noise.
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35.
Asymmetric Keys:
A.
Two related keys, a public key and a private key, that are used to perform complementary operations, such as encryption and decryption or signature verification
B.
A digital document issued and digitally signed by the private key of a Certification Authority that binds the name of a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the corresponding private key.
C.
A cryptographic algorithm that uses two related keys, a public key and a private key. The two keys have the property that deriving the private key from the public key is computationally infeasible.
D.
A set of policies, processes, server platforms, software and workstation used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.
Correct Answer A. Two related keys, a public key and a private key, that are used to perform complementary operations, such as encryption and decryption or signature verification
Explanation Asymmetric keys refer to a pair of related keys, a public key and a private key, which are used for performing complementary operations like encryption and decryption or signature verification. This means that the public key can be used to encrypt data or verify signatures, while the private key is used for decryption or signing. The use of two different keys with complementary functions adds an extra layer of security to cryptographic operations.
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36.
Public Key Certificate:
A.
Two related keys, a public key and a private key, that are used to perform complementary operations, such as encryption and decryption or signature verification
B.
A digital document issued and digitally signed by the private key of a Certification Authority that binds the name of a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the corresponding private key.
C.
A cryptographic algorithm that uses two related keys, a public key and a private key. The two keys have the property that deriving the private key from the public key is computationally infeasible.
D.
A set of policies, processes, server platforms, software and workstation used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.
Correct Answer B. A digital document issued and digitally signed by the private key of a Certification Authority that binds the name of a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the corresponding private key.
Explanation A public key certificate is a digital document that is issued by a Certification Authority and is digitally signed with their private key. It binds the name of a subscriber to a public key and serves as proof that the subscriber has sole control and access to the corresponding private key. This ensures the authenticity and integrity of the public key and allows for secure communication and authentication in various applications.
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37.
Public Keys Cryptography Algorithm:
A.
Two related keys, a public key and a private key, that are used to perform complementary operations, such as encryption and decryption or signature verification
B.
A digital document issued and digitally signed by the private key of a Certification Authority that binds the name of a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the corresponding private key.
C.
A cryptographic algorithm that uses two related keys, a public key and a private key. The two keys have the property that deriving the private key from the public key is computationally infeasible.
D.
A set of policies, processes, server platforms, software and workstation used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.
Correct Answer C. A cryptographic algorithm that uses two related keys, a public key and a private key. The two keys have the property that deriving the private key from the public key is computationally infeasible.
Explanation Public Key Cryptography is a cryptographic algorithm that uses two related keys, a public key and a private key. These keys have the property that deriving the private key from the public key is computationally infeasible. This means that even if the public key is known, it is extremely difficult to determine the corresponding private key. This property ensures the security of the encryption and decryption process, as well as the verification of digital signatures. Public Key Cryptography is widely used in various applications, such as secure communication, digital signatures, and secure online transactions.
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38.
Public Key Infrastructure:
A.
Two related keys, a public key and a private key, that are used to perform complementary operations, such as encryption and decryption or signature verification
B.
A digital document issued and digitally signed by the private key of a Certification Authority that binds the name of a subscriber to a public key. The certificate indicates that the subscriber identified in the certificate has sole control and access to the corresponding private key.
C.
A cryptographic algorithm that uses two related keys, a public key and a private key. The two keys have the property that deriving the private key from the public key is computationally infeasible.
D.
A set of policies, processes, server platforms, software and workstation used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.
Correct Answer D. A set of policies, processes, server platforms, software and workstation used for the purpose of administering certificates and public-private key pairs, including the ability to issue, maintain, and revoke public key certificates.
Explanation The correct answer explains that Public Key Infrastructure (PKI) is a comprehensive system consisting of policies, processes, server platforms, software, and workstations. Its main purpose is to administer certificates and public-private key pairs. This includes the ability to issue, maintain, and revoke public key certificates. PKI ensures the secure exchange of information by utilizing two related keys, a public key and a private key, which are used for encryption, decryption, signature verification, and other complementary operations.
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39.
Public-key encryption has ___ ingredients:
A.
5
B.
6
C.
7
D.
4
Correct Answer B. 6
Explanation Public-key encryption has 6 ingredients.
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40.
RSA was presented in
A.
1969
B.
1977
C.
1979
D.
1991
Correct Answer B. 1977
Explanation RSA, which stands for Rivest-Shamir-Adleman, is a public-key encryption algorithm that was developed by Ron Rivest, Adi Shamir, and Leonard Adleman. It was first presented in 1977, making it the correct answer. RSA is widely used in various applications, including secure communication, digital signatures, and secure online transactions.
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41.
Public key cryptosystem provides authentication:
A.
True
B.
False
Correct Answer A. True
Explanation Public key cryptosystem provides authentication by using a pair of keys, a public key and a private key. The public key is freely available to anyone, while the private key is kept secret by the owner. When someone wants to authenticate themselves, they can use their private key to encrypt a message, and anyone with the corresponding public key can decrypt it. This process verifies the identity of the sender, as only the owner of the private key could have encrypted the message. Therefore, public key cryptosystem provides authentication.
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42.
Public key cryptosystem provides confidentiality:
A.
True
B.
False
Correct Answer A. True
Explanation Public key cryptosystem provides confidentiality because it uses a pair of keys - a public key and a private key. The public key is used to encrypt the data, while the private key is used to decrypt it. Only the intended recipient with the private key can decrypt and access the confidential information. This ensures that the data remains secure and confidential during transmission and storage.
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43.
Public key cryptosystem provides availability:
A.
True
B.
False
Correct Answer B. False
Explanation Public key cryptosystem provides confidentiality and integrity, but not availability. Availability refers to the ability of a system to be accessible and usable when needed. Public key cryptosystems do not directly address availability concerns, as they primarily focus on ensuring secure communication and data protection. Availability is typically addressed through other means such as redundancy, backups, and disaster recovery plans. Therefore, the given answer is false.
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44.
In RSA:
A.
P – prime, q – any number
B.
P – any number, q – prime
C.
P,q – prime
D.
P,q – any numbers
Correct Answer C. P,q – prime
Explanation The correct answer is p,q – prime. In RSA encryption, the security relies on the difficulty of factoring large composite numbers into their prime factors. Therefore, both p and q need to be prime numbers in order to ensure the security of the encryption. If either p or q is not prime, it would make the encryption vulnerable to attacks.
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45.
The first published public-key algorithm
A.
Diffie-Hellman
B.
RSA
C.
Elgamal
D.
AES
Correct Answer A. Diffie-Hellman
Explanation Diffie-Hellman is considered the first published public-key algorithm because it was the first algorithm to introduce the concept of exchanging keys over a public channel without compromising security. It allows two parties to securely establish a shared secret key over an insecure communication channel. This algorithm is based on the mathematical problem of discrete logarithm, and it laid the foundation for modern public-key cryptography.
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46.
The purpose of Diffie-Hellman algorithm:
A.
To enable two users to securely exchange a key that can then be used for asymmetric encryption of message
B.
To enable two users to securely exchange a key that can then be used for symmetric encryption of message
C.
To enable two users to insecurely exchange a key that can then be used for asymmetric encryption of message
D.
To enable two users to insecurely exchange a key that can then be used for symmetric encryption of message
Correct Answer B. To enable two users to securely exchange a key that can then be used for symmetric encryption of message
Explanation The purpose of the Diffie-Hellman algorithm is to enable two users to securely exchange a key that can then be used for symmetric encryption of messages. This algorithm allows the users to establish a shared secret key over an insecure channel, without actually transmitting the key itself. This shared key can then be used for symmetric encryption, where both parties can encrypt and decrypt messages using the same key. This ensures that only the intended recipients can read the encrypted messages, providing confidentiality and security in the communication.
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47.
Difficulty of Diffie-Hellman algorithm depends on:
A.
Prime factorization
B.
Computing discrete logarithm
C.
Euler’s totient function
D.
Euclid’s formula
Correct Answer B. Computing discrete logarithm
Explanation The difficulty of the Diffie-Hellman algorithm depends on computing the discrete logarithm. This refers to the challenge of finding the exponent to which a given number must be raised to obtain another given number, within a specific mathematical group. The computational complexity of solving this problem is what makes the Diffie-Hellman algorithm secure, as it is believed to be a difficult task for an attacker to compute the discrete logarithm efficiently.
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48.
Message privacy means that sender and receiver expect:
A.
Integrity
B.
Confidentiality
C.
Authentication
D.
Nonrepudiation
Correct Answer B. Confidentiality
Explanation Message privacy refers to the protection of the content of a message from unauthorized access or disclosure. It ensures that only the intended recipient can access and understand the message. Confidentiality is an essential aspect of message privacy, as it ensures that the information remains private and cannot be accessed or understood by unauthorized parties. It involves encryption and other security measures to prevent unauthorized access to the message content. Therefore, the expectation of confidentiality is crucial for maintaining the privacy of messages between sender and receiver.
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49.
An encryption algorithm transforms plaintext into
A.
Cipher text
B.
Plain text
C.
Empty text
D.
Filled text
Correct Answer A. Cipher text
Explanation An encryption algorithm is designed to convert plaintext into cipher text. This process involves the use of mathematical operations and a secret key to scramble the original message, making it unreadable to anyone who does not possess the key. The resulting cipher text can only be decrypted back into the original plaintext using the correct key. Therefore, the correct answer is "Cipher text."
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50.
Ciphers of today are called round ciphers because they involve
A.
Single Round
B.
Double Rounds
C.
Multiple Round
Correct Answer C. Multiple Round
Explanation Ciphers of today are called round ciphers because they involve multiple rounds. This means that the encryption process is repeated multiple times, with each round adding an additional layer of complexity to the cipher. By using multiple rounds, the cipher becomes more secure and resistant to attacks. Each round typically includes a combination of substitution, permutation, and other cryptographic operations to ensure the confidentiality and integrity of the data being encrypted. Overall, the use of multiple rounds enhances the security of modern ciphers.