The term "software independence" (SI) was coined by Dr. Ron Rivest and NIST researcher John Wack. A software independent voting machine is one whose tabulation record does not rely solely on software. The goal of an SI system is to definitively determine whether all votes were recorded legitimately or in error.
The technical definition of SI is: 
A voting system is software-independent if an undetected change or error in its software cannot cause an undetectable change or error in an election outcome.
SI has been redefined as a global property for a tabulation of votes rather than of each individual vote, aiming to detect rather than prevent error and fraud through human processes.
Election officials and vendors have appropriately responded to the growing complexity of voting systems by adding more stringent access controls, encryption, testing, and physical security to election procedures and systems. The TGDC has considered current threats to voting systems and, at this time, finds that security concerns do not warrant replacing deployed voting systems where EAC Best Practices are used.
To provide auditability and proactively address the increasing difficulty of protecting against all prospective threats, the TGDC directs STS to write requirements for the next version of the VVSG requiring the next generation of voting systems to be software independent. The TGDC directs STS and HFP to draft usability and accessibility requirements to ensure that all voters can verify the independent voting record.
The TGDC further directs STS and Core Requirements and Testing Subcommittees (CRT) to draft requirements to ensure that systems that produce independently verifiable voting records are reliable and provide adequate support for audits.
- Requiring Software Independence in VVSG 2007: STS Recommendations for the TGDC Archived 2009-11-28 at the Wayback Machine., A draft white paper, not representing NIST policy
- Rivest, Ron and Wack, John (2006). "On the notion of "software independence" in voting systems" (PDF). DRAFT Version July 28, 2006. Retrieved 2007-02-15.
- Four Approaches to SI and Accessibility, Prepared at the direction of the HFP and STS Subcommittees of the Technical Guidelines Development Committee (TGDC) (This paper has been prepared by the National Institute of Standards and Technology at the direction of the HFP and STS subcommittees of the TGDC. It may represent preliminary research findings and does not necessarily represent any policy positions of NIST or the TGDC.)
- Resolutions Adopted by the TGDC at the December 4 and 5 Plenary Session
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