The RSA Algorithm uses which mathematical concept as the basis of its encryption?

A.
Geometry

B.
16-round ciphers

C.
PI (3.14159…)

D.
Two large prime numbers

Explanation:
RSA is derived from the last names of its inventors, Rivest, Shamir, and Addleman.
This algorithm is based on the difficulty of factoring a number, N, which is the product of two large prime
numbers. These numbers may be 200 digits each. Thus, the difficulty in obtaining the private key from the
public key is a hard, one-way function that is equivalent to the difficulty of finding the prime factors of N.
In RSA, public and private keys are generated as follows:
Choose two large prime numbers, p and q, of equal length, compute p3q 5 n, which is the public modulus.
Choose a random public key, e, so that e and (p – 1)(q – 1) are relatively prime.
Compute e x d = 1 mod (p – 1)(q – 1), where d is the private key.
Thus, d = e–1 mod [(p – 1)(q – 1)]
From these calculations, (d, n) is the private key and (e, n) is the public key.
Incorrect Answers:
A: The RSA Algorithm does not use Geometry as the basis of its encryption.
B: The RSA Algorithm does not use 16-round ciphers as the basis of its encryption.
C: The RSA Algorithm does not use PI as the basis of its encryption.

Krutz, Ronald L. and Russel Dean Vines, The CISSP Prep Guide: Mastering the Ten Domains of Computer
Security, John Wiley & Sons, New York, 2001, p. 148