Ukraine's SBU is declassifying the files selectively
Ukraine is opening up part of its old KGB archive, declassifying hundreds of thousands of documents spanning the entire Soviet period.
But the move to expose Soviet-era abuses is dividing Ukrainians, the BBC's Gabriel Gatehouse reports from Kiev.
Deep in the bowels of Ukraine's former KGB headquarters there is a deathly silence. Thousands of boxes, piled floor to ceiling, line the walls. Each box is carefully numbered and each one contains hundreds of documents: case notes on enemies of the former Soviet state.
Behind each number, there is a story of personal tragedy.
Volodymyr Viatrovych, the chief archivist, pulled out a brown cardboard folder stuffed full of documents: case number 4076. At the centre of the case is a letter, dated 1940 and addressed to "Comrade Stalin, the Kremlin, Moscow".
Ivan Severin was "liquidated" in 1947, his case notes state
"Dear Iosif Vissarionovich," the letter starts. Nikolai Reva wanted Stalin to know the facts about the great famine of 1932-33, when millions died as a result of the Soviet policy of forced collectivisation.
Like many at the time, Mr Reva believed that Stalin was being kept in the dark, and that if only he knew what was happening, he would surely put a stop to it.
But his letter landed him in the Gulag. He was eventually rehabilitated - 25 years later.
Many met a harsher fate.
Leafing through one of many macabre photo albums, Mr Viatrovych pointed to a picture of Ivan Severin, shot in the head by the Soviet security services. Under the picture, in very neat handwriting, is written: "Liquidated, 3 April 1947".
Mr Viatrovych and his team are helping people to find out what happened to relatives and loved ones, often decades after they disappeared.
Mr Viatrovych is helping the victims' relatives to uncover the truth
But the Ukrainian Security Service (SBU), now in charge of the files, is declassifying them selectively.
They are concentrating on older cases, like that of the "liquidated" Mr Severin, who was part of a guerrilla campaign against Soviet rule in western Ukraine after World War II.
The authorities are preparing to mount a criminal prosecution in relation to the famine, or Holodomor, as it is known in Ukraine, though it is doubtful whether there is anyone still alive to stand in the dock.
But SBU head Valentyn Nalyvaichenko hopes this is just the beginning.
"As soon as Russia starts to open and uncover its archives, there will be more and more truth about the real history," he said. At the moment, he added, Russia is not being especially co-operative.
But there is another obstacle to complete disclosure, and that is the Ukrainian Security Service itself. They are the ones deciding which files to declassify.
I put it to Mr Nalyvaichenko that the SBU is, after all, a successor to the KGB. He came out on the defensive.
"First and most important for me - we are not a successor to the KGB. That's according to the law," he said.
Could he state categorically that no-one working for the SBU today had formerly worked for the KGB?
He could not, admitting that 20% of his employees were former KGB officers. Some analysts in Ukraine believe that is a conservative figure.
It seems unlikely that SBU officers who worked for the Soviet KGB in the 1970s and 80s will be enthusiastic about declassifying documents that could incriminate them. Even if, as Mr Nalyvaichenko pointed out, the SBU is trying to recruit younger staff.
'Not worth it'
But not all young Ukrainians have an exclusively negative view of their 20th-Century history.
In Kiev, there is a vast monument to the Soviet victory over Nazi Germany: a sprawling bronze relief of soldiers bearing guns and bayonets.
"We love our history," said Svitlana, a young schoolteacher from the southern city of Odessa, on an outing with her class.
She was not keen for the children in her charge to be forced to examine the darker chapters of Soviet history.
"The past is the past," she said. "The history of the famine, the killings, all the things Stalin did. I don't think we should bring them up. There's enough violence today as it is. If we start blaming each other
It's just not worth it."
The idea of airing the past as part of a healing process, and excluding members of the former regime from positions of authority - a process known as "lustration" - is being actively promoted by some in the Ukrainian administration.
More than 200,000 bodies may be buried in Bykivnia, outside Kiev
But it is highly controversial. Dmytro Tabachnyk, a historian and opposition lawmaker, thinks the notion is absurd.
"It's a witch hunt," he said. "To start a process of lustration after 18 years of independence would lead society to the brink of civil war."
In a forest just outside Kiev, the tree trunks are tied with thousands of white scarves.
The scarves are embroidered in the traditional Ukrainian way, with red-and-black geometric patterns, and each one symbolically represents a life lost to Soviet oppression.
Under Stalin, the Soviet secret police would bury executed political prisoners at Bykivnia. No-one knows exactly how many bodies lie buried in this wood, but some estimates put the figure at more than 200,000.
But, says Nico Lange, the German director of the Konrad Adenauer Foundation in Kiev, Ukrainians must stop blaming the Russians for their past, and start looking inward.
"Ukrainians have a tendency to perceive themselves as only victims of those historical processes," he says.
"But coming to terms with the past really starts when you start uncovering also your own involvement: the oppressions by your own state, the offenders who are from your own people. If you do this work, this very painful work, the truth will finally set you free. And you will not invite new dictators to oppress you again."
The Germans have experience of confronting their own past, both following World War II, and after the fall of the Berlin Wall.
But it will take a lot of united political will for such a process to get under way in Ukraine.
And it may be that, for the moment, there are still too many people alive and in positions of power, who were involved with the Soviet regime in one way or another.