A Public Key Infrastructure (PKI) is a system that provides the services and mechanisms for creating, managing, distributing, using, storing, and revoking digital certificates, which are electronic documents that bind a public key to an identity. A digital certificate can be used to authenticate the identity of an entity, such as a person, a device, or a server, that possesses the corresponding private key. An organization can implement a partial PKI with only the servers having digital certificates, which means that only the servers can prove their identity to the clients, but not vice versa. The security benefit of this implementation is that servers can authenticate themselves to the client, which can prevent impersonation, spoofing, or man-in-the-middle attacks by malicious servers. Clients can authenticate themselves to the servers, mutual authentication is available between the clients and servers, and servers are able to issue digital certificates to the client are not the security benefits of this implementation, as they require the clients to have digital certificates as well. References: CISSP All-in-One Exam Guide, Eighth Edition, Chapter 5, Cryptography and Symmetric Key Algorithms, page 615. Official (ISC)2 CISSP CBK Reference, Fifth Edition, Chapter 5, Cryptography and Symmetric Key Algorithms, page 631.
