Which of the following allows computation and analysis of data within a ciphertext without knowledge of the plaintext?

Options:

A Lattice-based cryptography
B Quantum computing
C Asymmetric cryptography
D Homomorphic encryption   Note : someone is saying answer is answer C and other is saying D i am confused ... please help to guide the same 

Consider a very simple symmetric block encryption algorithm in which 32-bits blocks of
plainext are encrypted using a 64-bit key. Encryption is defined as
C = (P⊕K0 ) ⊞ K1

where C = ciphertext, K = secret key, K0 = leftmost 64 bits of K, K1 = rightmost 64 bits of K,
⊕ = bitwise exclusive OR, and ⊞ is addition mod 264
.

a) Show the decryption equation. That is, show the equation for P as a function of C, K0,
and K1.
b) Suppose and adversary has access to two sets of plaintexts and their corresponding
ciphertexts and wishes to determine K. We have the two equations:

C = (P⊕K0 ) ⊞ K1 ; C’

= (P’⊕K0 ) ⊞ K1

First, derive an equation in one unknown (e.g., K0). Is it possible to proceed further to
solve for K0?

Which of the following are differences between RADIUS and TACACS+?

1. RADIUS uses TCP; TACACS+ uses UDP.
2. RADIUS encrypts the entire packet contents; TACACS+ only encrypts the password.
3. RADIUS supports more protocols than TACACS+.
4. RADIUS combines authentication and authorization into a single function; TACACS+ allows these services to be split between different servers

27. In a packet switched computer network which of the following statements is true? a) If a packet is lost or damaged, then the entire message needs to be retransmitted. b) Network devices need to have sufficient memory to store all packets for a given message. c) All packets belonging to the same message must use the same route for a given destination. d) The latency is lower than a message switched network, since the first packet can be sent right away without waiting for other packets to be ready. x e) None of the above