What service should be used to prevent the loss of access to documents encrypted with a private key?

Using key escrow is essential in preventing the loss of access to documents encrypted with a private key. Key escrow involves securely storing a copy of the private key with a trusted third party, which allows for recovery of the key if the original is lost or becomes inaccessible. This is particularly important for organizations that handle sensitive data and need to ensure that they can retrieve their encrypted documents if their key is lost due to theft, misplaced keys, or other forms of data loss.

In this scenario, if an individual loses their private key, they could potentially lose access to all information encrypted with that key. By utilizing key escrow, organizations create a backup option that can be utilized under circumstances that would normally lead to data loss, providing an extra layer of security and access continuity.

The other options, while related to security, do not serve the same purpose of key recovery. RA, OCSP, and CSP relate to aspects of certificate management and validation, but they do not address the specific need for recovering lost private keys. Key escrow fills this crucial gap, making it the most suitable service in the context of preventing access loss to encrypted documents.