Hongkongers can begin registering on Friday to take part in Occupy Central's vote on how the city's leader should be elected.
Signing up in advance will mean voters can skip verification procedures when Occupy hosts its "referendum", according to University of Hong Kong polling chief Dr Robert Chung Ting-yiu.
HKU's public opinion programme has been commissioned by Occupy to organise the June 20-22 vote, at which all the city's registered voters will be able to choose between three electoral reform proposals shortlisted by 2,500 Occupy activists.
Occupy, which plans to block streets in Central if the government fails to come up with an acceptable plan for the 2017 chief executive poll, will adopt the winner as its favoured reform model.
Chung said the pre-registration would serve as a "trial run". People can take part by using the Pop Vote smartphone app, but not the popvote.hk website, from Friday until June 18. They will be asked to answer two mock questions and to verify their identity by text message.
Chung admitted that the Occupy vote was "entirely different" from an official referendum overseas: organised by the government and with a result that, in most cases, is legally binding.
"It is not legally binding … but has moral power," he said.
He is confident the system can handle up to 800,000 votes - online and in person, but said his program had come under attack from hackers, just as it did when it hosted a mock election for chief executive in 2012. Two computers were shut down on May 27 and 28.
The server has been upgraded to fend off hackers, he added.
Chung has long been under a different kind of attack from Beijing loyalists, who accuse him of being an agent for foreign powers. "Those who cast doubt on our work, in my opinion, definitely have a political mission," he said. "The only way to respond is to do our job in a more professional and transparent way."
Pro-establishment newspapers yesterday questioned whether Occupy was guilty of laundering money by funnelling foreign donations through the account of the Democratic Development Network, which Occupy uses as it has not been allowed to register as a company.
Occupy co-organiser Dr Chan Kin-man dismissed the reports as an attempt at suppression and said the group did not receive foreign money.
The movement's secretariat said that it used the account to manage its finances, with the network's consent, adding the practice was legal and reasonable as the money raised so far was donated by Hongkongers and merely spent on lawful activities. Police refused to comment on "individual cases".