Encryption Has a Remarkably Long and Varied History

Multiple Choice

Encryption has a remarkably long and varied history.The invention of writing was apparently soon followed by a desire to conceal messages.One of the earliest methods,attributed to an ancient Roman emperor,was the simple substitution of numbers for letters,for example A = 1, B = 2,etc.This is an example of

A) a hashing algorithm.
B) symmetric key encryption.
C) asymmetric key encryption.
D) a public key.