When the two executives from accountancy firm PriceWaterhouseCoopers arrive on the Oscars red carpet on Sunday, they already know whose names are inside the envelopes and who will be going home empty handed.

It is the final act of a months-long voting process conducted under watertight security.

Unusually for an era when electronic voting systems are used to elect governments or presidents, the Oscars vote count is conducted entirely by hand, with Oltmanns and Rosas supervising a small team from a secret location.

The preference for hand counting would appear to be prudent. Academy of Motion Picture Arts and Sciences executive director Bruce Davis said the body's computers are regularly targeted by hackers.

"This is not information that we want sitting around on a computer somewhere," Davis said.

The results speak for themselves: in the 74 years that the auditing giants have overseen the voting process, there has never been a single leak.

Counters of the 5,829 ballots work in groups but are kept apart so they don't know each other's totals before the winners' envelopes are prepared.

When the winners are identified after three days of counting - usually around Saturday - the names are placed in two sets of envelopes that are then locked away.

On Oscars night, Rosas and Oltmanns take separate cars to the show each traveling by a different route to ensure they are not both caught up in one of Los Angeles' notorious traffic gridlocks.