Which of the following encryption algorithms does NOT deal with discrete logarithms?

A.
El Gamal

B.
Diffie-Hellman

C.
RSA

D.
Elliptic Curve

Explanation:
RSA does not deal with discrete logarithms.
RSA, named after its inventors Ron Rivest, Adi Shamir, and Leonard Adleman, is a public key algorithm that is
the most popular when it comes to asymmetric algorithms. RSA is a worldwide de facto standard and can be
used for digital signatures, key exchange, and encryption. It was developed in 1978 at MIT and provides
authentication as well as key encryption.
The security of this algorithm comes from the difficulty of factoring large numbers into their original prime
numbers. The public and private keys are functions of a pair of large prime numbers, and the necessary activityrequired to decrypt a message from ciphertext to plaintext using a private key is comparable to factoring a
product into two prime numbers.
Incorrect Answers:
A: El Gamal is a public key algorithm that can be used for digital signatures, encryption, and key exchange. It is
based not on the difficulty of factoring large numbers but on calculating discrete logarithms in a finite field.
B: The Diffie-Hellman algorithm enables two systems to generate a symmetric key securely without requiring a
previous relationship or prior arrangements. The algorithm allows for key distribution, but does not provide
encryption or digital signature functionality. The algorithm is based on the difficulty of calculating discrete
logarithms in a finite field.
D: The Elliptic Curve algorithm computes discrete logarithms of elliptic curves, which is different from
calculating discrete logarithms in a finite field.

Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, pp. 815, 818