BERLIN -- In the cavernous underground jail once run by East Germany's notorious Stasi security agency, Jorge Luís Vázquez leads a visitor into a dank, tiny, pitch-black cell, then slams the iron door shut.
The world vanishes into darkness. Moments later, the door swings open and light returns.
''Well, how was it?'' asks Vázquez, a Cuban exile who was jailed in one of these very Stasi cells in 1987, when East Germany was under communist rule, and now leads tours through the prison-turned-museum.
More importantly, he has found hundreds of East German government documents on Stasi relations with Cuba's own feared Ministry of the Interior, known as MININT, and is nearly finished writing what may well be the most thorough report to date on the links between the two security agencies.
Vázquez says he found the MININT is ''almost a copy'' of the repressive Stasi security system, exported by East Germany to Cuba in the 1970s and '80s, and that the ties between the two organizations run far deeper than previously known.
From how to bug tourist hotel rooms to an intriguing mention of the hallucinogenic LSD, the degree to which the Stasi trained and provided material and technical support to the security arm of Fidel Castro's regime had a sweeping and harsh impact on Cuba.
Germans taught the Cubans how to mount effective camera and wiretap systems for eavesdropping -- for example, at what height on the wall to install microphones, which color wallpaper provides the best concealment, and which shade of lighting for the best video recordings.
The Stasi provided computers and introduced new archiving methods that better organized, protected and sped up the Cubans' processing of security information. It delivered one-way mirrors used for interrogations and provided equipment to fabricate masks, mustaches and other forms of makeup so that when the Cubans sent out covert agents, ''they went in dressed with wigs, false noses -- the works -- credit of the Stasi,'' Vázquez says.
U.S. experts on Cuban security agencies agree with Vázquez's findings.
''East Germany had a major role in building up Cuban counterintelligence as well as its foreign intelligence services, providing training for decades . . . right up to the final days of East Germany,'' said Chris Simmon, a career U.S. counterintelligence officer and expert on Cuban intelligence.
And Cubans are still using what they learned from the Stasi, added Vázquez, 48.
''The repressive system that existed in East Germany . . . is the same one that exists today in Cuba,'' he says. ''What MININT learned from the Stasi has not been forgotten. On the contrary, [the strategies and techniques] are alive today despite the fall of the Berlin Wall.''
The Stasi's menacing control over almost every aspect of private and public life in East Germany can be seen in this year's Oscar-winning film The Lives of Others, the tale of a Stasi officer's inner conflict as he protects a dissident playwright whose apartment has been thoroughly bugged by the Stasi.
A FEARED AGENCY
Headquartered amid the grim Soviet-styled apartment blocks of the former East Berlin, the Stasi -- short for Staatssicherheit, or State Security -- succeeded through surveillance, intimidation and torture in becoming one of the most feared intelligence agencies in the world.
By the time the Berlin Wall collapsed in 1989, the Stasi had 91,000 employees and 350,000 collaborators in a country of 17 million.
When the Stasi archives were opened to the public in the early 1990s, East Germans learned that there had been 986 documented deaths at the prison and discovered 112 miles worth of files on their fellow citizens.
About the same distance as Havana to Key West, Vázquez joked during a tour of the museum, known as the Berlin-Hohenschoenhausen memorial.
Vázquez, who has brown mop-like hair and an excitable manner when he speaks, learned German while a teenage student in one of Cuba's language institutes.
He was later sent to East Germany as a translator for Cubans studying there, and from 1982 to 1987 lived in Karl-Marxstadt, now Chemnitz.
He also traveled widely throughout Eastern Europe, where his conversations with people about the daily hardships in Poland, Hungary and Czechoslovakia darkened his views of communism. It was Moscow, he says, that ''traumatized me the most, seeing the political and economic disaster of communism.''
But in 1987 Vázquez helped a visiting Cuban musician escape to Canada. He was arrested, interrogated for one week at the Stasi prison and then deported under armed guard to Cuba.
After several days at a Havana jail he describes as a ''medieval'' experience, spent in 'filthy, tiny cells with nothing to cover oneself with, listening to prisoners' screams,'' he was freed but blacklisted from most jobs.
He later married a German citizen, returned to Berlin in 1992 and in 1996 got to see his file in the Stasi archives. He began his research in 2002 and has dug up hundreds of files, read through thousands of pages of official documents and published dozens of articles in Miscellanea, a Swiss-based Cuban exile magazine.
And now he's putting the finishing touches on his report, ''The Havana-Berlin Connection: State Secrets and Notes on the Collaboration between the Stasi and MININT.'' He is now looking to publish the Spanish-language report in book form.
''I want to provoke a change,'' he says. ''When a security system has its own prisons, judges, lawyers and interrogators and no one controls them, as in Cuba, then the state security is what's sustaining the Communist Party, and repression is what's sustaining the Cuban regime.
''I want to hold the Cuban government responsible; I want to denounce it for its collaboration with the Stasi.''
But the materials on Stasi-Cuban cooperation that he has uncovered speak for themselves.
The Stasi reconstructed MININT's telephone and communications system in 1988 to better facilitate eavesdropping. Before that, in 1981, it modernized MININT's printing press to enable better, faster production of party propaganda -- and false passports used for espionage and subversion, Vázquez says.
The Stasi also overhauled the security system at José Martí International Airport in Havana, installing cameras, migration control booths and state-of-the-art X-ray equipment that mirrored identically the security methods in East Germany.
Coordinated espionage efforts between the Stasi and MININT also helped widen the Cuban secret service's intelligence gathering. Vázquez's study reveals that in 1985, Operation Palma Real, a cooperative action of ''electronic espionage'' by German and Cuban agents, resulted in valuable interceptions of U.S. telephone and telegraph communications from the U.S. Navy base at Guantánamo, Cuba.
Furthermore, the Stasi trained Cuban guerrillas who were being sent abroad to subvert other governments, teaching observation, espionage and interrogation techniques that considerably expanded Cuba's impact on conflicts ranging from Central America to Africa, according to the documents Vázquez has gathered.
''What we see is a copy of the Stasi system that spread across the developing world -- from Angola, Ethiopia and Mozambique to Nicaragua, Guatemala and El Salvador,'' as Cubans passed on the methodology and technology to others, he said.
And then there was that intriguing mention of LSD, in a letter from the MININT's supply department formally requesting from the Stasi some 360 doses of the hallucinogenic. The document does not explain its use.
But Stasi-MININT relations were not always warm.
Vázquez said the Stasi frequently criticized its Caribbean counterparts for being disorganized, carelessly leaking information to American spies and failing to master the use of secret codes.
''It was a cultural confrontation: the Cubans were one way -- not punctual, for example -- and the Germans were the opposite,'' Vázquez said.
And some Stasi methods simply didn't work in Cuba.
Storing the scents of dissidents so they could be tracked down by dogs if needed, a technique used in East Germany, did not work in the hot and humid tropics, according to the documents that Vázquez located.
In the 18 years since the Berlin Wall fell, the former East Germany has made perhaps more effort than any other Soviet Bloc country to open up the security files kept on its citizens, and face the dark questions that still haunt its past.
Now, Vázquez hopes, his study's publication can serve as ''a base for others, from Poland to Bulgaria, to do similar investigations'' across Eastern Europe.