Putin might not know the specific person who hacked the DNC, but certainly he. Or at least the government he rubs are responsible. It is almost always Rilussia. In all the movies it is Russia. They have the means and the motive and they have never been comfortable with the American political system and the American government.
Putin might be responsible. I wouldn't doubt it. He is a strong person with strong influence. He is surrounded by a government that is obedient to him just as our government is obedient to our president. If we have a Secret Service and a CIA that investigates for us, who is to say other countries don't have similar task forces?
Putin is responsible for the hack of the U.S. Democratic Party's e-mails. Despite his denials, there have been accusations from officials in the United States, which are not done lightly, particularly against a foreign government. It fits in with Putin's profile and his history of being sneaky. He is an ex-KGB agent.
Putin may have authorized the program that got in, but he would be foolish to be actively involved in its execution. He has an image as a strongman to maintain - for that image, he can't been seen to be dealing with every technocrat and level of government directly. His job is to lead, not to run.