One means of securing iSCSI devices from unwanted intrusion is to require that the host, or initiator, be authenticated by the iSCSI device, or target, whenever the host attempts to access data on the target LUN.
The goal of authentication is to prove that the initiator has the right to access a target, a right granted when you configure authentication.
ESXi does not support Secure Remote Protocol (SRP), or public-key authentication methods for iSCSI. You can use Kerberos only with NFS 4.1.
ESXi supports both CHAP and Mutual CHAP authentication. the vSphere Storage documentation explains how to select the best authentication method for your iSCSI device and how to set up CHAP.
Ensure uniqueness of CHAP secrets. The mutual authentication secret for each host should be different; if possible, the secret should be different for each client authenticating to the server as well. This ensures that if a single host is compromised, an attacker cannot create another arbitrary host and authenticate to the storage device. With a single shared secret, compromise of one host can allow an attacker to authenticate to the storage device.