In modern versions of Zerto (specifically starting with Zerto 9.0 and 9.5), the security model for site pairing was significantly enhanced to move away from legacy credential sharing. To establish a secure relationship between two Zerto Virtual Managers (ZVMs), the administrator must utilize a Pairing Token.

Architecturally, the pairing process works as a "push-pull" handshake. The administrator first logs into the Target (Remote) ZVM—the site that will receive the replication—and navigates to the "Sites" tab. There, they select the option to "Generate Pairing Token." This token is a unique, time-sensitive alphanumeric string that acts as a one-time password for the pairing attempt. Once generated, the administrator copies this token and logs into the Source (Local) ZVM. During the "Pair" wizard, they specify the IP address or FQDN of the remote ZVM and paste the pairing token.

According to the HPE Advanced Storage Solutions implementation guides, this token replaces the need for the source site to know the administrative credentials of the remote vCenter or ZVM, thereby adhering to the principle of least privilege. The token typically has a default expiration (e.g., 48 hours) or expires immediately after a successful pairing session. This ensures that even if a token is intercepted, its window of utility is minimal. Options A and B are incorrect as they represent legacy or non-standard methods; while vCenter credentials are required for the initial installation and registration of the ZVM, they are not the mechanism used for the pairing handshake itself. Option D is incorrect as Zerto manages the underlying encryption keys automatically once the pairing is authenticated via the Pairing Token.