Multi-level secure JTAG architecture

Increases in the powerful features being deployed through the JTAG interface has left the testing platform vulnerable to malicious users. In this paper the hardware implementation of a flexible multilevel security access system is described. The security mechanism allows for higher granularity for controlling user access of individual scan chains. This allows for blocking of individual opcodes from being loaded into scan chains. The hardware modifications proposed are complaint with IEEE 1149.1 and require no modifications to the core logic of the IC.