Systems and methods for implementing access control by systems-on-chip (SoCs). An example SoC may comprise an access control unit employed to: receive a message comprising an access control data item; validate the message using a value of a message digest function of contents of the message and a value of a state variable reflecting a state of communications between the access control unit and a programming agent that has initiated the message, wherein the value of the state variable is derived from a previous value of the message digest function calculated within a current communication session between the access control unit and the programming agent; update the state variable using the value of the message digest function of the contents of the message; and control, using the access control data item, access by an initiator device to a target device.