iSCSI CHAP is supported on the FlashArray for unidirectional or bidirectional authentication. Enabling CHAP is optional and up to the discretion of the user. Please refer to the following post for a detailed walkthrough:
http://www.codyhosterman.com/2015/03/configuring-iscsi-chap-in-vmware-with-the-flasharray/
Note:
Please note that iSCSI CHAP is not currently supported with dynamic iSCSI targets on the FlashArray. If CHAP is going to be used, you MUST configure your iSCSI FlashArray targets as static targets.