VATICAN CITY, March 8 (Reuters) - For centuries the Roman Catholic Church counted on the walls of the Sistine Chapel to keep the process of electing a new pope secret. But the Vatican must now turn to an electronic arsenal in the face of tweeting cardinals and a year of crushing leaks.
Security is foremost as the red-hatted princes of the Church gather in Rome to elect the successor to Pope Benedict, the first pontiff in centuries to resign after a reign plagued by the 'Vatileaks' scandal, when his butler photocopied and leaked secret documents alleging corruption in the Holy See.
The word "conclave" means "with key" in Italian, and comes from a Latin term referring to a room that can be locked. But closed doors are no longer enough in the 21st century.
Workmen are preparing the Sistine Chapel, where the secret vote is expected to take place next week, by laying down a false floor over its ornate tiles and installing electronic jammers to block any signals escaping from within the 15th-century chapel, site of Michelangelo's vast fresco "The Last Judgment".
Prior to the vote, Vatican officials will sweep the chapel and the guesthouse that houses the cardinals with anti-bugging scanners to detect any hidden microphones.
No stranger to surveillance, Vatican police tapped several phonelines within the city state last year in their investigation into whether insiders helped butler Paolo Gabriele to leak documents to an Italian journalist in early 2012.
As chamberlain of the Church, it is Cardinal Tarcisio Bertone's responsibility to ensure secrecy, together with three selected cardinal assistants, and they can employ two trusted technicians to help.
Their job is vast. The use of any kind of technology to record or transmit voices, images or text from within the conclave is forbidden, and cardinals swear never to reveal its proceedings unless ordered to do so by the new pope.
Television, radio and all news from the outside world are also banned. Cardinals are forbidden to communicate with anyone on the outside, unless they have special permission for "extremely grave and urgent reasons".
Up to the election of Pope John Paul II, cardinals attending the conclave slept on cots with temporary partitions between them in halls and apartments adjacent to the Sistine Chapel, with the often-aged cardinals sharing limited toilet facilities.
John Paul updated the rules governing the conclave to address new technologies in 1996 and built the Domus Sanctae Marthae, a guesthouse run by nuns that has enough simple rooms to house all the cardinals. Rooms are allocated by lots.
The electors will be guarded by Vatican police as they walk the few hundred metres (yards) from the guesthouse door around the back of St. Peter's Basilica to the Sistine Chapel. They will also have the choice of taking a Vatican bus.
The entire area will be cordoned off and Vatican personnel authorised to enter will have to walk through metal detectors.
But above all, the Vatican has appealed to the cardinals' own consciences not to break the rules. "We are counting on people's morality and responsibility," Lombardi told reporters this week.
Each cardinal swears an oath of secrecy on the Gospel when he enters the Sistine Chapel.
"We promise and swear with the maximum loyalty to observe, both with clerics and laymen, the secrecy of all that regards the election of the Roman pontiff and what takes place in the place of election," are the words of the promise.
The handful of nuns, doctors and assistants who help run the conclave, face automatic excommunication from the Church if they break the pact.
The official concern about leaks is no surprise. Ahead of the conclave, prelates have fed strategic information to the press, possibly to favour their chosen candidates or issues.
Vatican officials on Wednesday told cardinals to stop speaking to the media and cancelled a press briefing at the last minute, after Italian newspapers wrote detailed accounts of who said what in pre-conclave discussions about the future pontiff.
"I don't know who is violating the pact of secrecy," Vatican spokesman Father Federico Lombardi told reporters. "If anyone knows who is violating this, they should say so."
And this time round, the Holy See must contend with a new foe: Twitter.
Despite the blackout, Roger Mahony, pressured not to attend over a sexual abuse cover-up in the United States, continued to feed information over Twitter on Thursday and Friday, noting a "mood of excitement" and announcing when all 115 electors had arrived in Rome.
Three other cardinals - Timothy Dolan of New York, Christoph Schoenborn of Vienna and Jean-Pierre Ricard of Bordeaux, France - also posted or published articles in their home countries on Friday that spoke of their Vatican discussions in general terms. (Additional reporting by Philip Pullella, editing by Tom Heneghan and Michael Roddy)