Which of the following correctly describes the difference between public key cryptography and public key infrastructure?

A.
Public key cryptography is the use of an asymmetric algorithm, while public key infrastructure is the use of a symmetric algorithm.

B.
Public key cryptography is used to create public/private key pairs, and public key infrastructure is used to perform key exchange and agreement.

C.
Public key cryptography provides authentication and nonrepudiation, while public key infrastructure provides confidentiality and integrity.

D.
Public key cryptography is another name for asymmetric cryptography, while public key infrastructure consists of public key cryptographic mechanisms.

Explanation:
D: Public key cryptography is asymmetric cryptography; the terms are used interchangeably. Public key cryptography is one piece in a public key infrastructure (PKI), which is made
up of many different parts, including certificate authorities, registration authorities, certificates, keys, programs, and users. The infrastructure contains the pieces that will identify users,
create and distribute certificates, maintain and revoke certificates, distribute and maintain encryption keys, and enable all technologies to communicate and work together for the
purpose of encrypted communication and authentication.
A is incorrect because PKI uses a hybrid system of symmetric and asymmetric key algorithms and methods. Public key cryptography is the use of an asymmetric algorithm. Thus,
the terms asymmetric cryptography and public key cryptography are interchangeable and mean the same thing. Examples of asymmetric algorithms are RSA, elliptic curve
cryptosystem (ECC), Diffie-Hellman, and El Gamal.
B is incorrect because public key cryptography is the use of asymmetric algorithms, which are used to create public/private key pairs, perform key exchange or agreement, and
generate and verify digital signatures. Public key infrastructure, on the other hand, is not an algorithm, a protocol, or an applicationit is an infrastructure based on symmetric and
asymmetric cryptography.
C is incorrect because a PKI does not provide authentication, nonrepudiation, confidentiality, and integrity directlyit can use algorithms that provide these security services. A PKI
uses asymmetric, symmetric, and hashing algorithms. Symmetric algorithms provide confidentiality, asymmetric algorithms provide authentication and nonrepudiation, and hashing
algorithms provide integrity.