1.4 Relationship to Other Protocols
PKCA is defined as a Kerberos pre-authentication extension ([RFC4120] section 3.1.1). This extension is used in the Kerberos AS exchange [RFC4556], and therefore PKCA relies on a working Kerberos infrastructure and a certificate authority (CA) for issuing [X509] certificates. PKCA includes the use of elliptic curve cryptography (ECC). ECC support [RFC5349] relies upon a CA issuing ECC certificates. Applications already using Kerberos can use PKCA without modifications.
In order to support NTLM authentication [MS-NLMP] for applications connecting to network services that do not support Kerberos authentication, when PKCA is used, the KDC returns the user's NTLM one-way function (OWF) in the privilege attribute certificate (PAC) PAC_CREDENTIAL_INFO buffer ([MS-PAC] section 2.6.1).