Which of the following is not a characteristic of the El Gamal algorithm?
A.
It is an extension of the Diffie-Hellman algorithm
B.
Its main downfall is its speed
C.
It can be used for digital signatures, encryption, and key agreement
D.
It is a public key algorithm
Explanation:
El Gamal is a public key algorithm that can be used for digital
signatures, encryption, and key exchange. It is not based on the difficulty of
factoring large numbers, but is based on calculating discrete logarithms in a finite
field and is really is an extension of the Diffie-Hellman algorithm. Although El
Gamal provides the same type of functionality as some of the other asymmetric
algorithms, its main drawback is performance. When compared to other algorithms,
this algorithm is usually the slowest.
“C” is just as much a characteristic of El Gamal as the others. All four are correct.
I would think so too, the first sentence in the answer explanation is actually choice C
If you take a closer look, “key exchange” in the explanation is not the same as “key agreement” in answer C. That’s why it is the correct answer for “not a characteristic of the El Gamal algorithm”.