1. A trusted platform field upgrade system, comprising: a trusted platform module (TPM) comprising a volatile memory configured to store a first physical presence flag and a second physical presence flag, and a non-volatile memory configured to store an owned flag, wherein a state of the owned flag is not dependent on a state of either the first physical presence flag or the second physical presence flag; wherein the first physical presence flag can be in either a presence asserted state or a presence not asserted state and is set during a pre-OS boot sequence based on assertion of physical presence during the pre-OS boot sequence and maintains its state after the pre-OS boot sequence; wherein the second physical presence flag is set to a presence asserted state during the pre-OS boot sequence based on assertion of physical presence during the pre-OS sequence and is cleared after the pre-OS boot sequence; and if a field upgrade for the TPM is received after the pre-OS boot sequence, the trusted platform field upgrade system determines whether to implement the field upgrade based, at least in part, on the owned flag, wherein: if the owned flag is in an unowned state, the field upgrade of the TPM is implemented only if the first physical presence flag is in the presence asserted state; and if the owned flag is in an owned state, the field upgrade of the TPM is implemented only if an ownership credential for the TPM is authenticated.