The section called Breaking Substitution Ciphers (p. 166) describes a "random substitution cipher," in which each letter of the alphabet is randomly replaced with a different letter or character i. e. A→T, B→F ... What makes a random substitution cipher more secure than a Caesar shift?

Answer: Compared to a Caesar shift, the random substitution cipher offers many more possibilities, because the encryption is randomly chosen.

Explanation:

A Caesar Cipher is also a type of substitution cipher, but instead of doing it randomly, it shifts the alphabet by a certain number of characters. Therefore, the answer to decrypt the message is simply to figure out that number.