Which of the following techniques can be used by an administrator while working with the
symmetric encryption cryptography?
Each correct answer represents a complete solution. Choose all that apply.

A.
Block cipher

B.
Stream cipher

C.
Transposition cipher

D.
Message Authentication Code

Explanation:
An administrator can use the following techniques while working with the symmetric
encryption cryptography:
1.Block cipher: A block cipher is a symmetric key cipher which operates on fixed-length groups of
bits, termed blocks, with an unvarying
transformation. A block cipher encryption algorithm might take a 128-bit block of plaintext as input,
and output a corresponding 128-bit
block of ciphertext. The exact transformation is controlled using a second input the secret key.
Decryption is similar to the encryption
process. The decryption algorithm takes a 128-bit block of ciphertext together with the secret key,
and gives up the original 128-bit
block of plaintext.
2.Stream cipher: A stream cipher is a symmetric key cipher where plaintext bits are combined with a
pseudorandom cipher bit stream,
typically by an exclusive-or (xor) operation. In a stream cipher the plaintext digits are encrypted one
at a time, and the transformation
of successive digits varies during the encryption. It is also called a state cipher because the
encryption of each digit depends on the
current state. In practice, the digits are typically single bits or bytes. Stream ciphers typically execute
at a higher speed than block
ciphers and have lower hardware complexity.
3.Message Authentication Code (MAC): Message authentication code (MAC) is a mechanism that
applies an authentication scheme and
a secret key to a message, so that the message can only be verified by the intended recipient. It
provides integrity checks based on the
secret key. Typically, message authentication codes are used between two parties that share a
secret key to authenticate information
transmitted between them.
Answer option C is incorrect. Transposition cipher cannot be used with the symmetric encryption
cryptography.