ballots are used to determine the official vote, not the electronic record. The voter has the ability to proofread the ballot before it is placed into the scanner/lockbox and have it voided if there is any error, just as has always been possible with existing manual voting systems. Attachment of a printer to DRE voting machines that print an encrypted receipt that is either retained by the voter or stored within the machine. If the receipt is retained, the receipts can be manually counted and compared to the electronic vote totals in the event of a dispute. These systems have not been used in elections in the United States. Creation of an encrypted audit trail at the same time the electronic ballot is created in a DRE voting machine, a form of witness system. The audit trail can be accessed and compared to the electronic vote totals in the event of a dispute. Use of precinct-based optical scan or mark-sense tabulators instead of DREs. In this simple and cost-effective system, voters fill out paper ballots which are then counted electronically by a tabulator at the precinct, similar to the technology used to score standardized tests. Optical scan machines have been in use for decades, and provide a voter-verified audit trail by default. Tabulators can detect overvotes at the poll so that the voter can be given the opportunity to correct a spoiled ballot. Systems that allow the voters to prove how they voted do not conform to the generally accepted definition of voting by secret ballot, as such proof raises the risk of voter intimidation and vote selling. As such, systems that allow such proof are generally forbidden under the terms of numerous international agreements and domestic laws. Professor Avi Rubin has testified in front of the United States House Committee on House Administration in favor of voting systems that use a paper ballot and disfavoring systems that use retrofitted VVPAT attachments. He has said on his personal blog that "after four years of studying the issue, I now believe that a DRE with a VVPAT is not a reasonable voting system." An auditable system, such as that provided with VVPAT, can be used in randomized recounts to detect possible malfunction or fraud. With the VVPAT method, the paper ballot can be treated as the official ballot of record. In this scenario, the ballot is primary and the electronic records