It is standard for digital certificates which invlove and enables:
Message digest
Digital Signature
Encryption
Digital Certificate
It establish the relation between user and key.
Authentic file from trusted parties .
Fields of digital certificate
Version
Signature Algortihnm
Issuer USERID
CA digital signature
Certifiaction Authority
They are the trusted agency that can issue digital certificates
Registration Authority
It assures the valid and correct registration of requests for digital certificates and authenticating the entity making the request . It is also subordinate CA . Initally the end entity which is registering and initializing , it goes through RA and after that it moves to CA for key air recovery . And then it is issued certificate which is cross checked/validated in CA which is part of PKI management.
