According to Rob Pegoraro at the Faster Forward blog, the District "will let overseas voters cast ballots online using open-source, standards-based software, not the closed, proprietary mechanisms that have dominated electronic voting throughout its troubled history in the United States."
A Palo Alto, Calif., developer of election software, Open Source Digital Voting Foundation, will provide the new system. According to company representatives, starting with September's primary election, D.C. residents serving overseas and others far out of town won't have to choose between voting by mailed-in paper ballot or a faxed or e-mailed ballot.
"Instead," Pegoraro writes, "after applying to vote online -- using the same kinds of forms required to obtain an absentee ballot today -- overseas voters will receive a one-time personal identification number. They'll use the PIN to log on to an encrypted site hosted by the District, on which they will fill out a PDF form and submit that under two forms of encryption -- one to confirm the integrity of the ballot, a second to attest that it was completed by the holder of the PIN.
"Voters will be able to check online to see that their ballot (or, for the first time this year, their mailed-in form) was received. The D.C. Board of Elections and Ethics will confirm receipt of the ballot and then discard the identifying information attached to the ballot itself."
Go to the Faster Forward post for more details.