Using ipmitool, I can successful poll values with this command, for example:

ipmitool -I lanplus -H 10.10.10.10 -U zabbix -P password -y 10A191A90A3B13DFAEC4EF4968C777287CA0FADE4 -L User sdr

However, in the Zabbix Host IPMI tab, there's any area where I can include the encryption key: 10A191A90A3B13DFAEC4EF4968C777287CA0FADE4