2
Computer Security Fundamentals Midterm Exam with precise || || || || || ||
detailed answers
|| ||
What does encryption do? - ✔✔Obfuscates a message (plaintext)
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In symmetric encryption, the keys are ______.
|| || || || || ||
In asymmetric encryption, the keys are ______. - ✔✔the same.
|| || || || || || || || || ||
different.
What do the initials 'CIA' stand for? - ✔✔Confidentiality
|| || || || || || || || ||
Integrity
Availability
In a passive attack, the adversary attempts to: - ✔✔learn or make use of information from
|| || || || || || || || || || || || || || || ||
the system without affecting system resources
|| || || || ||
In an active attack, the adversary attempts to: - ✔✔alter system resources or affect their
|| || || || || || || || || || || || || || ||
operation
Using the Caesar cipher, what is the ciphertext with p = "ATTACKNOW" and k='C'? -
|| || || || || || || || || || || || || || ||
✔✔CVVCEMPQY
List three applications where authentication is needed and how it is implemented - ✔✔1.
|| || || || || || || || || || || || || ||
Credit card, PIN || ||
2. Car, keys
|| ||
3. Yourself, SSN
|| ||
, 2
How many keys are used in symmetric encryption? - ✔✔One
|| || || || || || || || ||
How many keys are used in asymmetric encryption? - ✔✔Two
|| || || || || || || || ||
The length of a key in a symmetric encryption scheme is 16 bits. Roughly how many tries
|| || || || || || || || || || || || || || || || ||
are needed in a brute-force attack to break this encryption scheme? - ✔✔2^16
|| || || || || || || || || || || ||
How long should the length of a key for a symmetric encryption scheme be? - ✔✔At least
|| || || || || || || || || || || || || || || || ||
128 bits
||
Using the keyword MONARCHY, construct a Playfair Key Matrix and encrypt the plaintext
|| || || || || || || || || || || || ||
'ATTACKNOWX' - ✔✔RSSRDEANXZ || ||
Using the Vigenere cipher with the keyword 'deceptive', encrypt the plaintext
|| || || || || || || || || || ||
'wearediscoveredsaveyourself' - ✔✔ZICVTWQNGRZGVTWAVZHCQYGLMGJ || ||
Using the Row transposition cipher with key 4312567, encrypt the plaintext
|| || || || || || || || || || ||
'attackpostponeduntiltwoamxyz' - ✔✔TTNAAPTMTSUOAODWCOIXKNLYPETZ || ||
State one steganography technique - ✔✔The sequence of first letters of each word in a
|| || || || || || || || || || || || || || ||
message
True or False: using a one-time pad, the ciphertext bears no statistical relationship to the
|| || || || || || || || || || || || || || ||
plaintext. - ✔✔True || ||
True or False: using a one-time pad, given an observed ciphertext and the first t-bits of the
|| || || || || || || || || || || || || || || || ||
plaintext, the probability that the next bit of plaintext is 0 is 1/2. - ✔✔True
|| || || || || || || || || || || || || ||
Computer Security Fundamentals Midterm Exam with precise || || || || || ||
detailed answers
|| ||
What does encryption do? - ✔✔Obfuscates a message (plaintext)
|| || || || || || || ||
In symmetric encryption, the keys are ______.
|| || || || || ||
In asymmetric encryption, the keys are ______. - ✔✔the same.
|| || || || || || || || || ||
different.
What do the initials 'CIA' stand for? - ✔✔Confidentiality
|| || || || || || || || ||
Integrity
Availability
In a passive attack, the adversary attempts to: - ✔✔learn or make use of information from
|| || || || || || || || || || || || || || || ||
the system without affecting system resources
|| || || || ||
In an active attack, the adversary attempts to: - ✔✔alter system resources or affect their
|| || || || || || || || || || || || || || ||
operation
Using the Caesar cipher, what is the ciphertext with p = "ATTACKNOW" and k='C'? -
|| || || || || || || || || || || || || || ||
✔✔CVVCEMPQY
List three applications where authentication is needed and how it is implemented - ✔✔1.
|| || || || || || || || || || || || || ||
Credit card, PIN || ||
2. Car, keys
|| ||
3. Yourself, SSN
|| ||
, 2
How many keys are used in symmetric encryption? - ✔✔One
|| || || || || || || || ||
How many keys are used in asymmetric encryption? - ✔✔Two
|| || || || || || || || ||
The length of a key in a symmetric encryption scheme is 16 bits. Roughly how many tries
|| || || || || || || || || || || || || || || || ||
are needed in a brute-force attack to break this encryption scheme? - ✔✔2^16
|| || || || || || || || || || || ||
How long should the length of a key for a symmetric encryption scheme be? - ✔✔At least
|| || || || || || || || || || || || || || || || ||
128 bits
||
Using the keyword MONARCHY, construct a Playfair Key Matrix and encrypt the plaintext
|| || || || || || || || || || || || ||
'ATTACKNOWX' - ✔✔RSSRDEANXZ || ||
Using the Vigenere cipher with the keyword 'deceptive', encrypt the plaintext
|| || || || || || || || || || ||
'wearediscoveredsaveyourself' - ✔✔ZICVTWQNGRZGVTWAVZHCQYGLMGJ || ||
Using the Row transposition cipher with key 4312567, encrypt the plaintext
|| || || || || || || || || || ||
'attackpostponeduntiltwoamxyz' - ✔✔TTNAAPTMTSUOAODWCOIXKNLYPETZ || ||
State one steganography technique - ✔✔The sequence of first letters of each word in a
|| || || || || || || || || || || || || || ||
message
True or False: using a one-time pad, the ciphertext bears no statistical relationship to the
|| || || || || || || || || || || || || || ||
plaintext. - ✔✔True || ||
True or False: using a one-time pad, given an observed ciphertext and the first t-bits of the
|| || || || || || || || || || || || || || || || ||
plaintext, the probability that the next bit of plaintext is 0 is 1/2. - ✔✔True
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