Thank you for the suggestion. As I said above, there is nothing preventing something like that from being implemented in ZFS in the future. Unfortunately, howev

Thank you for the suggestion. As I said above, there is nothing preventing something like that from being implemented in ZFS in the future. Unfortunately, however, the encryption implementation uses a port of the Illumos Kernel Crypto Framework, which has not yet implemented an SIV mode. As far as using our own HMAC goes we are using a standard SHA512-HMAC implementation which should be just as secure.