A bridge CA is not primarily used for issuing end-user certificates, managing CRLs, or encrypting data. Its main purpose is to facilitate trust between multiple PKIs.
A bridge CA in PKI serves as a trust intermediary between multiple PKIs or CA domains. It doesn’t directly issue certificates to end-users, but instead issues cross-certificates to the root or policy CAs of different PKI domains. This creates a network of trust relationships, allowing entities in one PKI to validate and trust certificates issued by CAs in other PKIs, without requiring direct cross-certification between every pair of CAs. Bridge CAs are often used in large-scale, multi-organizational PKI deployments to simplify trust relationships and interoperability.