The use of text in a book as the algorithm to decrypt a message is known as the ____ cipher.
A) substitution
B) transposition
C) running key
D) Vernam

Question

Quizplus · Accepted Answer

The running key cipher involves using a piece of text, such as a book, to generate a random alphanumeric key that is then used to decrypt a message. This method is a form of polyalphabetic substitution, as opposed to a simple substitution cipher (A) or a transposition cipher (B). The Vernam cipher (D) is also a polyalphabetic substitution cipher but it uses a completely random key, rather than a piece of text.

The Use of Text in a Book as the Algorithm