A Certifying Authority is a trusted body whose central responsibility is to issue, revoke, renew and provide directories of Digital Certificates. In real meaning, the function of a Certifying Authority is equivalent to that of the passport issuing office in the Government. Similar to a passport, a user's certificate is issued and signed by a Certifying Authority and acts as a proof.  

Under the IT Act 2000, CA has to establish the required infrastructure and obtain the license from the Controller of Certifying Authority, Ministry of Information Technology, Government of India.

A Sub CA means a Certifying Authority falling under the CA trust hierarchy.

A Registration Authority (RA) is responsible for initiating the certificate issuance process after receiving approved application request from the Local Registration Authority. Revocation requests for Digital Certificates from subscribers/ authorized representative of the subscriber are also handled by the RA.

An LRA (Local Registration Authority) is an agent of the Certifying Authority who collects the application forms for Digital Signature Certificates and related documents, does the verification and approves or rejects the application based on the results of the verification process.