Network Defense Essentials (NDE) Practice Exam 2025 – Your All-in-One Resource to Exam Success!

The process that is accurately described involves substituting units of plaintext with ciphertext; this is known as substitution. In cryptographic terms, substitution refers to the method where elements of the plaintext (the original data) are replaced with corresponding elements from a predefined set, which makes up the ciphertext (the encoded data).

This process can involve replacing single characters, groups of characters, or even entire blocks of data, depending on the specific algorithm being employed. For example, in a basic substitution cipher, each letter in the plaintext is replaced with another letter from the alphabet based on a systematic rule. This makes the plaintext unreadable without the proper key to reverse the substitution.

While encryption as a broader process also involves converting plaintext into ciphertext, this term encompasses various methods, including both substitution and transposition. Decryption, conversely, is the process of converting ciphertext back into plaintext, which does not involve substitution. Transposition involves rearranging the characters in the plaintext rather than replacing them, distinguishing it from substitution. Thus, the terms are closely related but refer to different aspects of cryptographic methods.