Protected JTAG

In this paper, we consider a particular aspect of an effort to define trusted computing solutions. One of the hardware features of an embedded device is the JTAG (joint test action group) port that allows easy access to a processor for debugging purposes. This access is a potential security threat in a high assurance environment. This paper presents a solution of a protected JTAG. The purpose of providing protected JTAG, as part of the trusted computing platform, is to prevent access to private and confidential information by unauthorized users and yet allow debugging functions. The presented solution introduces different levels of access. The level of user's access is based on the user's permissions.