"Here you're simply wrong -- the nuclear transfer was *from* Pakistan *to* North Korea. In particular, the Koreans got their uranium enrichment technology from the Paks (Khan sent them centrifuges)."

N Korea history before 1980:
1962: North Korea sets up an atomic energy research center with Soviet help.
1964: Chinese help prospect for uranium.
1967: North Korea starts up small Soviet-supplied reactor.
1969-70: Soviet Union sends FROG-5 and FROG-7A missiles to North Korea.
1974: North Korea joins IAEA (International Atomic Energy Agency).
1975: North Korea produces first plutonium -- a few grams.
1976: In return for military aid during the 1973 Middle East war, Egypt sends Soviet Scud-B missiles to North Korea.
1977: North Korea agrees to international inspection of Soviet-supplied equipment.
1977: Kang Song-San, a high party official, visits China's Lop Nur nuclear test site.
1979: Starts to build 30-megawatt thermal reactor that can produce enough plutonium for one bomb a year.
http://www.wisconsinproject.org/countries/nkorea/nuke-miss-chron.htm

That Pakistan is manufacturing and selling centrifuges doesn't does mean it's transfering technology. The Pakistan has more access than N Korea to a manfacturing base. It could selling centrifuges like Japan sell consumer goods- but obviously dangerous and illegal consumer goods which should not be sold or traded.
But checking this I see I was wrong in sense in that I was assuming that China wasn't directly assist Pakistan. But instead China was known to be assisting an non signatory state:
"Chinese assistance in the development of gas centrifuges at Kahuta was indicated by the presence of Chinese technicians at the facility in the early 1980s. The uranium enrichment facility began operating in 1984, but suffered serious start up problems."
http://www.fas.org/nuke/guide/pakistan/facility/kahuta.htm
And:
"In the 1990s Pakistan began to pursue plutonium production capabilities. With Chinese assistance, Pakistan built the 40 MWt (megawatt thermal) Khusab research reactor at Joharabad, and in April 1998, Pakistan announced that the reactor was operational. According to public statements made by US officials, this unsafeguarded heavy water reactor generates an estimated 8-10 kilotons of weapons grade plutonium per year, which is enough for one to two nuclear weapons. The reactor could also produce tritium if it were loaded with lithium-6. According to J. Cirincione of Carnegie, Khusab's plutonium production capacity could allow Pakistan to develop lighter nuclear warheads that would be easier to deliver with a ballistic missile.
http://66.218.71.225/search/cache?p=Pakistan+%2B+nuclear+reactor&prssweb=Search&ei=UTF-8&fl=0&u=www.fas.org/nuke/guide/pakistan/nuke/&w=pakistan+nuclear+reactor&d=39BC54DCAF&icp=1&.intl=us

If true that China offerred this much technological assistance, there would be less that N Korea could offer.
It's fair safe to assume that everything N Korea knows about nuclear technology it got from Soviets or China.
With Khan connection, there the possiblity of Pakistan passing some western technology to China. And China giving more technology to Pakistan than it gave to N Korea. Therefore I suppose I could be wrong.
But what suspect is more likely is Khan technology was uranium enrichment- though even this might be of interest to China. Because it was "classified URENCO uranium enrichment plant in the Netherlands" and don't know why Netherlands would be place there much bomb making going on.