In almost any other country, having the United States accuse your government of hacking into a major American corporation would be a cause for concern. But North Korea isn't like most other countries. For decades, the North Korean regime has skillfully used manufactured crises to maintain its grip on power. So when President Obama publicly accused the regime of Kim Jong Un of carrying out the Sony attacks, the regime saw an opportunity for some trolling.
"As the United States is spreading groundless allegations and slandering us, we propose a joint investigation with it into this incident," the North Korean foreign ministry said on Saturday.
The regime claims that "without resorting to such tortures as were used by the US CIA, we have means to prove that this incident has nothing to do with us."
Obviously the jab at the CIA is ridiculous. Whatever you think of the CIA's abuses, the human rights violations of the North Korean regime are infinitely worse.
But this isn't a serious proposal, and it's unlikely the regime would actually cooperate with a US investigation. When news of the hack first broke, North Korea played coy, saying that people should "wait and see." North Korea doesn't seem to care if people actually think they were behind the attack. Rather, their goal seems to be to create endless drama, in order to ensure that they'll never be ignored by the United States.
The US government isn't buying North Korea's denials. "We are confident the North Korean government is responsible for this destructive attack," a US spokesman said, according to the BBC. "If the North Korean government wants to help, they can admit their culpability and compensate Sony for the damages this attack caused."
Update: I've added information about the US response.