A network stream needs to be encrypted. Sara, the network administrator, has selected a cipher
which will encrypt 8 bits at a time before sending the data across the network. Which of the
following has Sara selected?
A.
Block cipher
B.
Stream cipher
C.
CRC
D.
Hashing algorithm
In modern cryptography, symmetric key ciphers are generally divided into STREAM CIPHERS and BLOCK CIPHERS.
Block ciphers operate on a fixed length string of bits. The length of this bit string is the block size. Both the input (plaintext) and output (ciphertext) are the same length; the output cannot be shorter than the input – this follows logically from the pigeonhole principle and the fact that the cipher must be reversible — and it is undesirable for the output to be longer than the input.
So:
• A block cipher encrypts data into fixed-length groups of bits, called a block.
• In this question, the cipher is transmitting the data one block at a time.
An example of a block cipher algorithm that works on chunks of data–encrypting one and then moving to the next is BLOWFISH.
Blowfish is an encryption system that performs a 64-bit block cipher at very fast speeds.
MEMORIZARION HINT: How do you eat a blowfish? A chunk (block) at the time!
0
0