A Viterbi decoder and its hardware Trojan models: an FPGA-based implementation study

Varsha Kakkara; Karthi Balasubramanian; B Yamuna; Deepak Mishra; Karthikeyan Lingasubramanian; Senthil Murugan

doi:10.7717/peerj-cs.250

A Viterbi decoder and its hardware Trojan models: an FPGA-based implementation study

PeerJ Comput Sci. 2020 Mar 2:6:e250. doi: 10.7717/peerj-cs.250. eCollection 2020.

Authors

Varsha Kakkara^#¹, Karthi Balasubramanian¹, B Yamuna¹, Deepak Mishra², Karthikeyan Lingasubramanian³, Senthil Murugan^#⁴

Affiliations

¹ Department of Electronics and Communication Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore, Tamil Nadu, India.
² Digital Communication Division (DCD), Optical and Digital Communication Group (ODCG), Satcom Navigation Payload Area (SNPA), Space Application Center (SAC), ISRO, Ahmedabad, Gujarat, India.
³ Electrical and Computer Engineering, University of Alabama, Birmingham, AL, USA.
⁴ Department of Electronics and Communication Engineering, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Amritapuri, Kerala, India.

^# Contributed equally.

Abstract

Integrated circuits may be vulnerable to hardware Trojan attacks during its design or fabrication phases. This article is a case study of the design of a Viterbi decoder and the effect of hardware Trojans on a coded communication system employing the Viterbi decoder. Design of a Viterbi decoder and possible hardware Trojan models for the same are proposed. An FPGA-based implementation of the decoder and the associated Trojan circuits have been discussed. The noise-added encoded input data stream is stored in the block RAM of the FPGA and the decoded data stream is monitored on the PC through an universal asynchronous receiver transmitter interface. The implementation results show that there is barely any change in the LUTs used (0.5%) and power dissipation (3%) due to the insertion of the proposed Trojan circuits, thus establishing the surreptitious nature of the Trojan. In spite of the fact that the Trojans cause negligible changes in the circuit parameters, there are significant changes in the bit error rate (BER) due to the presence of Trojans. In the absence of Trojans, BER drops down to zero for signal to noise rations (SNRs) higher than 6 dB, but with the presence of Trojans, BER doesn't reduce to zero even at a very high SNRs. This is true even with the Trojan being activated only once during the entire duration of the transmission.

Keywords: Bit error rate; Coded communication system; Hardware Trojan; Viterbi decoder.

Grants and funding

This work was supported by Space Application Center, ISRO through RESPOND project /ISRO/RES/3/732/16-17. Deepak Mishra from ISRO is a coauthor and was involved in the study design, analysis and preparation of the article.