Registration ( or we refer to as Enrollment or Credential Enrollment) is defined in RFC 4949 as:
1. (I) /information system/ A system process that (See: authentication information, credential, identifier, identity, Identity Proofing.)

2. (I) /PKI/ An administrative act or process whereby an entity's name and other attributes are established for the first time at a CA, prior to the CA issuing a digital Certificate that has the entity's name as the subject. (See: Registration Authority.)

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