The term PKI can be applied in different ways, depending on its exact purpose and meaning. It is the abbreviated form of public key infrastructure and can refer to the basis as to how digital signatures are created within digital certificates. The term can also apply to a special type of system, called a certificate authority or CA, which is needed to create such certificates.
PKI Requires Using a CA System and Following Standards
A PKI certificate authority system is the type of system required to create digital certificates. The various types of certificates -- those with digital signatures and those without -- can include a public key. Not all digital certificates have to contain a digital signature, and this is where confusion sometimes occurs, in regards to public key infrastructure. It should be noted that public key infrastructure is used to refer to the actual standard used to create digital signatures within the digital certificates.