Using instruction block signatures to counter code injection attacks

With more computing platforms connected to the Internet each day, computer system security has become a critical issue. One of the major security problems is execution of malicious injected code. In this paper we propose new processor extensions that allow execution of trusted instructions only. The proposed extensions verify instruction block signatures in run-time. Signatures are generated during a trusted installation process, using a multiple input signature register (MISR), and stored in an encrypted form. The coefficients of the MISR and the key used for signature encryption are based on a hidden processor key. Signature verification is done in the background, concurrently with program execution, thus reducing negative impact on performance. The preliminary results indicate that the proposed processor extensions will prevent execution of any unauthorized code at a relatively small increase in system complexity and execution time. 1