In cryptography, a center trusted by one or more agencies or individuals to create and assign certificates and, optionally, to create user's keys. 2. In secure communications, a trusted person or entity who issues certificates (also called "public- key certificates") for encryption purposes. 3. An independent party identifying and certifying payers and payees for real-time credit card transactions in electronic commerce. 4. Third level of the Public Key Infrastructure (PKI) Certification Management Authority responsible for issuing and revoking user certificates, and exacting compliance to the PKI policy as defined by-the parent Policy Creation Authority (PCA. )