Which
of the following types of ciphers are included in the historical ciphers? Each correct answer
represents a complete solution. Choose two.
A.
Block ciphers
B.
Transposition ciphers
C.
Stream ciphers
D.
Substitution ciphers
Explanation:
Historical ciphers include the following types of ciphers:
1.Substitution ciphers: In cryptography, a substitution cipher is a method of encryption by which
units of plaintext are replaced with
ciphertext according to a regular system. The units may be single letters, pairs of letters, triplets of
letters, mixtures of the above, and
so forth. The receiver deciphers the text by performing an inverse substitution.
2.Transposition ciphers: A transposition cipher is a method of cryptographic encryption by which the
positions held by units of plaintext
(which are commonly characters or groups of characters) are shifted according to a regular system,
so that the ciphertext constitutes a
permutation of the plaintext. That is, the order of the units is changed. Mathematically a bijective
function is used on the characters’
positions to encrypt and an inverse function to decrypt.
Answer options A and C are incorrect. Block ciphers and stream ciphers are not included in the
historical ciphers. Both are the types of modern
ciphers.