Kizspy | Question: 14
(Choose 1 answer)
Which of the followings describe the 2nd block encryption output (C2) of OFB mode? The followings are
given: E (an encryption cipher function), K (the key). C1 (the cipher output from the 1st block encryption), P2
(the plaintext for the 2nd block), P1 (the plaintext for the 1st block), and XOR (and exclusive-or function). For
example, XOR(x,y) indicate the bit-by-bit XOR between the two bit vectors x and y, and E(K,P1) is the
encryption output when using the key K and the plaintext P1
A. C2 XOR(E(C1),K)
B. C2 E(KXOR(C1,P1))
C. C2 = XOR(P2,E(K,XOR(C1, P2)))
D. C2 E(K,XOR(C1,P2))
E. C2 XOR(P2,E(K,XOR(C1,P1)))
F. C2 XOR(P1,E(K,XOR(C1, P1)))
