Story highlights German officials discovered al Qaeda documents encoded on porn video

CNN obtained access to details of the documents

Many shed light on future plots the terror group had planned, including on cruise ships

On May 16 last year, a 22-year-old Austrian named Maqsood Lodin was being questioned by police in Berlin. He had recently returned from Pakistan via Budapest, Hungary, and then traveled overland to Germany. His interrogators were surprised to find that hidden in his underpants were a digital storage device and memory cards.

Buried inside them was a pornographic video called "Kick Ass" -- and a file marked "Sexy Tanja."

Several weeks later, after laborious efforts to crack a password and software to make the file almost invisible, German investigators discovered encoded inside the actual video a treasure trove of intelligence -- more than 100 al Qaeda documents that included an inside track on some of the terror group's most audacious plots and a road map for future operations.

Future plots include the idea of seizing cruise ships and carrying out attacks in Europe similar to the gun attacks by Pakistani militants that paralyzed the Indian city of Mumbai in November 2008. Ten gunmen killed 164 people in that three-day rampage.

Terrorist training manuals in PDF format in German, English and Arabic were among the documents, too, according to intelligence sources.

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U.S. intelligence sources tell CNN that the documents uncovered are "pure gold;" one source says that they are the most important haul of al Qaeda materials in the last year, besides those found when U.S. Navy SEALs raided Osama bin Laden's compound in Abbottabad, Pakistan, a year ago and killed the al Qaeda leader

One document was called "Future Works." Its authorship is unclear, but intelligence officials believe it came from al Qaeda's inner core. It may have been the work of Younis al Mauretani, a senior al Qaeda operative until his capture by Pakistani police in 2011.

The document appears to have been the product of discussions to find new targets and methods of attack. German investigators believe it was written in 2009 -- and that it remains the template for al Qaeda's plans.

Investigative journalist Yassin Musharbash, a reporter with the German newspaper Die Zeit , was the first to report on the documents. One plan: to seize passenger ships. According to Musharbash, the writer "says that we could hijack a passenger ship and use it to pressurize the public."

Musharbash takes that to mean that the terrorists "would then start executing passengers on those ships and demand the release of particular prisoners."

The plan would include dressing passengers in orange jump suits, as if they were al Qaeda prisoners at Guantanamo Bay, and then videotaping their execution.

Lodin and a man called Yusuf Ocak, who allegedly traveled back to Europe with him, are now on trial in Berlin where they are pleading not guilty. Ocak was detained in Vienna two weeks after Lodin's arrest.

According to a senior Western counterterrorism official, their names were on a watch list, and when they handed over documents at a European border crossing, their names registered with counterterrorism agencies.

Both men have pleaded not guilty to terrorism charges. Ocak is also charged with helping to form a group called the German Taliban Mujahedeen, and is alleged to have made a video for the group threatening attacks in Germany.

Prosecutors believe the pair met at a terrorist training camp in Pakistan's tribal territories and were sent back to Europe to recruit a network of suicide bombers.

"We do not know what those men were up to but there are certain files of information that would make it plausible that they were probably thinking of a Mumbai-style attack," says Musharbash.

In the fall of 2010, a year after the document was written, European intelligence agencies were scrambling to investigate a Mumbai-style plot involving German and other European militants -- which sparked an unprecedented U.S. State Department travel warning for Americans in Europe.

"I think it is plausible to think that the 'Future Works' document is part of that particular project," says Musharbash.

"Future Works" suggests al Qaeda was an organization under great pressure, without a major attack to its name in several years, harried by Western intelligence. If anything, its predicament is even more dire today.

"The document delivers very clearly the notion that al Qaeda knows it is being followed very closely," Musharbash tells CNN. "It specifically says that Western intelligence agencies have become very good at spoiling attacks, that they have to come up with new ways and better plotting."

Part of the response, according to the document, should be to train European jihadists quickly and send them home -- rather than use them as fighters in Afghanistan and Pakistan -- with instructions on how to keep in secret contact with their handlers.

What emerges from the document is a twin-track strategy -- with the author apparently convinced that al Qaeda needs low-cost, low-tech attacks (perhaps such as the recent gun attacks in France carried out by Mohammed Merah ) to keep security services preoccupied while it plans large-scale attacks on a scale similar to 9/11.

Those already under suspicion in Europe and elsewhere would be used as decoys, while others would prepare major attacks.

That is yet to materialize, but Musharbash believes a complex gun attack in Europe is still on al Qaeda's radar.

"I believe that the general idea is still alive and I believe that as soon as al Qaeda has the capacities to go after that scenario, they will immediately do it," he says.