It is not clear what exactly were the nuclear secrets handed over by Dr Abdul Qadeer Khan.
President Musharraf has pardoned Abdul Qadeer Khan
But experts around the world agree that it included hardware, blueprints and designs.
The material is thought to have been handed over to Libya, Iran and North Korea over a 10-year period.
Some scientists argue that the material enabled all three countries to process their own uranium.
According to Andy Oppenheimer, a nuclear weapons expert from Jane's Information Group, information handed over by Dr Khan would have included designs for making a nuclear bomb and information on how to make enriched uranium.
But he says it is impossible to know exactly what was handed over because Dr Khan's dramatic television confession was vague on the subject.
"The exact details of what was handed over are highly sensitive and have been kept a closely guarded secret by the Pakistani Government," he said.
The consensus among experts is that Dr Khan handed over centrifuge designs and parts for the making of enriched uranium for nuclear warheads.
Centrifuge is the process by which uranium is enriched for use in nuclear weapons.
"The equipment used in centrifuge is very complicated and involves thousands of different components", said Mr Oppenheimer.
"At this stage it is impossible to say what centrifuge parts Dr Khan is alleged to have leaked," he said. "What
we do know is that the hardware and designs were shipped out of Pakistan in bits and pieces over a prolonged period of time.
"It would have been impossible for Dr Khan to have done this single-handedly unless there are no export regulations in Pakistan whatsoever," said Mr Oppenheimer.
Journalist Kamran Khan - one of Pakistan's top nuclear experts - says that Dr Khan began leaking information and equipment 10 years ago using middlemen in Dubai.
But he says it was not the latest technology: the warhead design information he supplied dates back to an early 1960s Chinese design.
Tip of iceberg
"In my view much of what Dr Khan handed over to the three countries was out of date information and equipment," he said, "but still it could still have helped them in their efforts to build a bomb."
Dr Khan is believed to have supplied the equipment and know-how from his laboratories founded nearly three decades ago near Islamabad.
Missile tests are often used to score diplomatic points
The International Atomic Energy Agency have described Dr Khan's activities at the "tip of the iceberg in nuclear trafficking".
But spokesman Mark Gwozdecky said there were doubts about the nuclear weapons capabilities of Libya, Iran and North Korea.
"We think Libya received uranium conversion devices and nuclear designs," he said, "but its nuclear programme is still in its early stages and its unclear how much know-how and equipment came from Pakistan.
"Likewise there is no concrete evidence that information received by Iran went towards nuclear weapons manufacture."
North Korea is thought to have acquired information and nuclear components from Pakistan in return for ballistic missile technology.
But in November President Musharraf said that all weapons deals with Pyongyang had been terminated following several visits to the Stalinist country by Dr Khan over the last 10 years.