Data Integrity Algorithms Questions and Answers – CCM, GCM and Key Wrapping – II

This set of Cryptography Questions & Answers for entrance exams focuses on “CCM, GCM and Key Wrapping”.

1. In GCM, we define S as S = GHASH(A||0^v||C||0^u||[len(A)]||[len(C)]). What is v defined as?
a) 64 ceil[len (A)/128] – len (A)
b) 64 ceil[len (C)/128] – len (C)
c) 128 ceil[len (A)/128] – len (A)
d) 128 ceil[len (C)/128] – len (C)
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2. When the length of the IV is not 96, then
a) we append the rest of the bits with 1*0 to make it 128 bits
b) we append the rest of the bits with 0*1 to make it 128 bits
c) we append the rest of the bits with 1*0 to make it 256 bits
d) we append the rest of the bits with 0s to make it 128 bits
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3. Which is not true for Key-Wrapping?
a) Used for small Plain Texts
b) It has a relatively higher throughput than other modes
c) It has block size of 64 bits
d) It has n+1 cipher blocks, for n plaintext block
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4. What is the value of A (0)?
a) F9*
b) A9*
c) A6*
d) F6*
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5. The cipher block is one block longer than the plaintext to accommodate the IV.
a) True
b) False
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6. The key Wrapping Algorithm provides confidentiality and data integrity.
a) True
b) False
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7. Which of the following is a valid disadvantage of the PRNG based on MAC function?
a) It has a high throughput
b) It takes twice the execution time
c) It is hardware intensive and can only work on high end processors
d) none of the mentioned
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8. “Specify in the correct order (from top to bottom), which Pseudo Random Number Generation schemes are represented here?
i)
m = [ n/outlen] w_o = V
W = the null string
For i = 1 to m
w_i = MAC(K,w_i-1)
W = W || wi
Return leftmost n bits of W
ii)
m = [n/outlen] W = the null string
For i = 1 to m
w_i = MAC(K,V || i)
W = W || w_i
Return leftmost n bits of W
iii)
m = [n/outlen] A(0) = V
W = the null string
For I = 1 to m
A(i) = MAC (K,A(i-1))
w_i = MAC (K, a(I) || v)
W = W || w_i
Return leftmost n bits of W”

a) NIST SP 800-90 ; TLS/WTLS ; IEEE 802.11
b) TLS/WTLS ; NIST SP 800-90 ; IEEE 802.11
c) IEEE 802.11 ; NIST SP 800-90 ; TLS/WTLS
d) NIST SP 800-90 ; IEEE 802.11 ; TLS/WTLS

Sanfoundry Global Education & Learning Series – Cryptography and Network Security.

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