Cryptography, cybercriminality

1. Which of the following sentences is true?

		a)	In symmetric key algorithms the same key is used both for encryption and decryption
		b)	In asymmetric key algorithms the same key is used both for encryption and decryption
		c)	The primary benefit of symmetric cryptography is that it allows people who have no pre-existing security arrangement to exchange messages securely
		d)	In symmetric cryptography every user has a pair of keys: a public key, which encrypts data, and a corresponding private, or secret, key for decryption

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2. Which of the following sentences is true?

		a)	In asymmetric key algorithms the same key is used both for encryption and decryption
		b)	AES (Advanced Encryption Standard) is an example of asymmetric key algorithms
		c)	The primary benefit of asymmetric cryptography is that it allows people who have no pre-existing security arrangement to exchange messages securely
		d)	The private and public keys are mathematically unlinked, so it is infeasible to derive the private key from the public key

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3. When public key cryptography is used to provide confidentiality

		a)	The public key of the receiver is used for ciphering the plaintext
		b)	The private key of the receiver is used for ciphering the plaintext
		c)	The public key of the sender is used for ciphering the plaintext
		d)	The private key of the sender is used for ciphering the plaintext

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4. When public key cryptography is used to provide authentication

		a)	The public key of the receiver is used for ciphering the plaintext
		b)	The private key of the receiver is used for ciphering the plaintext
		c)	The public key of the sender is used for ciphering the plaintext
		d)	The private key of the sender is used for ciphering the plaintext

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5. Regarding the modes of operation of block cipher algorithms, which of the following sentences is false?

		a)	Parallel encryption is possible in CBC mode
		b)	In ECB mode blocks can be reordered and the reordering or repetition of blocks can change the message
		c)	There is limited error-propagation in CBC mode
		d)	In ECB mode, the plaintext structural information is exposed

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6. Which of the following sentences is true regarding modes of operation in block cipher algorithms

		a)	CTR decryption mode is not parallelizable, but preprocessing is possible
		b)	Errors are not propagated when OFB is applied
		c)	CTR encryption mode is parallelizable, but preprocessing is not possible
		d)	Errors are not propagated when CFB is applied

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7. The state update mechanism

		a)	is independent of the plaintext in synchronous stream ciphers
		b)	is independent of the ciphertext in self-synchronising stream ciphers
		c)	depends of the ciphertext in synchronous stream ciphers
		d)	depends of the ciphertext in synchronous block ciphers

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8. Which of the following sentences is false regarding hybrid encryption:

		a)	The random key is needed for symmetric encryption of the plaintext
		b)	The length of the ciphertext can be smaller than the length of the plaintext
		c)	The random key is ciphered with the public key of the receiver
		d)	The advantage respect ciphering the data with public key encryption is the speed of symmetric encryption

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9. Regarding hash functions, is it false that:

		a)	The output has a fixed length
		b)	Two different messages always have different hashes
		c)	Hash functions are one-way
		d)	It is computationally infeasible to modify a message without changing the hash

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10. The digital signature must fulfil:

		a)	Signature can be transferable
		b)	Signature can be deniable
		c)	Signature must use some information unique to the sender
		d)	Signature digital provides authentication but not data integrity

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11. A digital certificate

		a)	bind together a public key with an identity by using a digital signature
		b)	bind together a private key with an identity by using a digital signature
		c)	It does not contain any digital signature
		d)	It is digitally signed by the owner of this certificate

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12. A digital certificate must be revoked when

		a)	The certificate has been distributed without owner permission
		b)	The validity period has expired
		c)	The owner entity is no longer in sole possession of the private key
		d)	The owner is 18 years old

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13. The certification authority

		a)	verifies the validity of the digital certificate
		b)	signs the digital certificate
		c)	has not any private key
		d)	has a public key only known by other certification authorities

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14. Which of the following sentences is false regarding the certificate revocation list (CRL)

		a)	It is a list of revoked certificates
		b)	It is a list of expired certificates
		c)	It is periodically published
		d)	It is digitally signed

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15. The use of digital certificates

		a)	enables the distribution of any kind of cryptographic key
		b)	enables private key distribution
		c)	enables symmetric key distribution
		d)	enables public key distribution

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16. In order to verify a digital signature, it is required

		a)	The knowledge of the public key of the sender
		b)	The knowledge of the private key of the sender
		c)	The knowledge of the symmetric key of the sender
		d)	The knowledge of the public key of the receiver

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17. Regarding cybercrime, which of the following sentences is false?

		a)	The deployment of viruses can not be considered cybercrime
		b)	Cybercrime requires the use of modern telecommunication networks
		c)	An effective incident response procedure includes forensic investigation
		d)	An effective incident response procedure includes containment of the threat

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18. Examples of active attacks are:

		a)	Masquerade, replay, eavesdropping, DoS
		b)	Modification of messages, replay, eavesdropping, DoS
		c)	Modification of messages, masquerade, eavesdropping, DoS
		d)	Modification of messages, masquerade, replay, DoS

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19. Examples of passive attacks are:

		a)	Masquerade, traffic analysis
		b)	DoS, masquerade
		c)	Traffic analysis, eavesdropping
		d)	Eavesdropping, masquerade

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20. Which of the following sentences is a bad prevention tip?

		a)	Keep the computer system up with the latest patches and updates
		b)	Choose strong passwords and keep them safe
		c)	Protect the personal information
		d)	Keep the original passwords in your routers

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