Tamper-resistant software system based on a finite state machine

Akito Monden, Antoine Monsifrot, Clark Thomborson

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Many computer systems are designed to make it easy for end-users to install and update software. An undesirable side effect, from the perspective of many software producers, is that hostile end-users may analyze or tamper with the software being installed or updated. This paper proposes a way to avoid the side effect without affecting the ease of installation and updating. We construct a computer system M with the following properties: 1) the end-user may install a program P in any conveniently accessible area of M; 2) the program P contains encoded instructions whose semantics are obscure and difficult to understand; and 3) an internal interpreter W, embedded in a non-accessible area of M, interprets the obfuscated instructions without revealing their semantics. Our W is a finite state machine (FSM) which gives context-dependent semantics and operand syntax to the encoded instructions in P; thus, attempts to statically analyze the relation between instructions and their semantics will not succeed. We present a systematic method for constructing a P whose instruction stream is always interpreted correctly regardless of its input, even though changes in input will (in general) affect the execution sequence of instructions in P. Our framework is easily applied to conventional computer systems by adding a FSM unit to a virtual machine or a reconfigurable processor.

Original languageEnglish
Pages (from-to)112-122
Number of pages11
JournalIEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
Issue number1
Publication statusPublished - Jan 2005
Externally publishedYes


  • Encryption
  • Obfuscation
  • Software protection
  • Software security

ASJC Scopus subject areas

  • Signal Processing
  • Computer Graphics and Computer-Aided Design
  • Electrical and Electronic Engineering
  • Applied Mathematics


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