Which one of the following best describes a process that splits the block of plaintext into two separate blocks, then applies the round function to…

Correct answer:

https://en.wikipedia.org/wiki/Feistel_cipher

Feistel cipher (also known as Luby–Rackoff block cipher) is a symmetric structure used in the

construction of block ciphers, named after the German-born physicist and cryptographer Horst

Feistel who did pioneering research while working for IBM (USA); it is also commonly known as a

Feistel network. A large proportion of block ciphers use the scheme, including the US Data

Encryption Standard, the Soviet-developed GOST and the more recent Blowfish and Twofish ciphers.

In a Feistel cipher, encryption and decryption are very similar operations, and both consist of

iteratively running a function called a "round function" a fixed number of times.

Incorrect answers:

Symmetric cryptography - Symmetric-key algorithms are algorithms for cryptography that use the

same cryptographic keys for both encryption of plaintext and decryption of ciphertext. The keys may

be identical or there may be a simple transformation to go between the two keys.

Substitution cipher -

is a method of encrypting by which units of plaintext are replaced with

ciphertext, according to a fixed system; the "units" may be single letters (the most common), pairs of

letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by

performing the inverse substitution.

Block ciphers - block cipher is a deterministic algorithm operating on fixed-length groups of bits,

called blocks. It uses an unvarying transformation, that is, it uses a symmetric key. They are specified

elementary components in the design of many cryptographic protocols and are widely used to

implement the encryption of large amounts of data, including data exchange protocols.