साइबर सुरक्षा, IT नीति र विद्युतीय कारोबार ऐन – Cyber Security, IT Policy & ETA MCQ
साइबर सुरक्षा, IT नीति र विद्युतीय कारोबार ऐन – कम्प्युटर र IT
Cyber Security, IT Policy & ETA · Computer & IT (Technical) · ४०४ प्रश्न
४०४ प्रश्न उपलब्ध। मोड छान्नुहोस्:
साइबर सुरक्षा, IT नीति र विद्युतीय कारोबार ऐन: प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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Why is the ECB (Electronic Codebook) mode of a block cipher considered insecure for most data?
सही उत्तर: ग) Identical plaintext blocks produce identical ciphertext blocks, revealing patterns
ECB encrypts each block independently, so repeated patterns (e.g., in images) remain visible; modes like CBC or GCM avoid this.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Kerckhoffs's principle states that a cryptosystem should remain secure even if:
सही उत्तर: ख) Everything about the system except the key is public
Security should depend only on the secrecy of the key, not on hiding the algorithm ('security through obscurity').
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which encryption scheme is proven to give perfect secrecy when the key is truly random, as long as the message, and never reused?
सही उत्तर: क) One-time pad
Shannon proved the one-time pad unbreakable under these conditions; its weakness is distributing such long keys.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A cipher that rearranges the positions of the plaintext letters without changing the letters themselves is a:
सही उत्तर: ख) Transposition cipher
In a transposition (e.g., rail fence) the letters stay the same but their order changes; substitution ciphers replace letters.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Using the Vigenère cipher with the key 'KEY', the plaintext 'HELLO' is encrypted as:
सही उत्तर: घ) RIJVS
Shifts are K=10, E=4, Y=24 repeated: H+10 = R, E+4 = I, L+24 = J, L+10 = V, O+4 = S.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a Diffie-Hellman exchange with p = 23 and g = 5, Alice chooses secret a = 6 and Bob chooses secret b = 15. What shared secret key do they compute?
सही उत्तर: क) 2
A = 5^6 mod 23 = 8 and B = 5^15 mod 23 = 19; Alice computes 19^6 mod 23 = 2 and Bob computes 8^15 mod 23 = 2.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In RSA with p = 3, q = 11 and public exponent e = 3, the private exponent is d = 7. What is the ciphertext of the message m = 4?
सही उत्तर: ग) 31
n = 3 × 11 = 33; c = m^e mod n = 4^3 mod 33 = 64 mod 33 = 31 (and 31^7 mod 33 gives back 4).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which protocol lets a browser check in real time whether a particular digital certificate has been revoked, instead of downloading a full revocation list?
सही उत्तर: घ) OCSP (Online Certificate Status Protocol)
OCSP queries the CA's responder for the status of one certificate, an alternative to downloading the whole CRL.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In a Public Key Infrastructure (PKI), the component that verifies the identity of applicants before the CA issues certificates is the:
सही उत्तर: ग) Registration Authority (RA)
The RA handles identity checks and registration, while the CA signs and issues the certificates.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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When creating a digital signature, the sender normally signs:
सही उत्तर: ख) The hash (message digest) of the message
Signing the fixed-length hash is faster than signing the whole message, and any change to the message changes the hash.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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