What did Lucius know about Tom Riddle's diary?

I have open before me two paperback books: the first, Harry Potter and the Chamber of Secrets; the second, Harry Potter and the Half-Blood Prince.

Why?

Because I'm comparing passages dealing with Tom Riddle's purpose in re-opening the Chamber from each novel. I had thought I would find discrepancies and inconsistencies between the second book, in which Riddle (through Ginny Weasely and his diary) actually re-opens the Chamber, and the sixth book, in which Dumbledore explains to Harry Horcruxes and what information the Head Master was able to glean from the events from Harry's second year at Hogwarts.

What did I find?

Remarkable consistency.

In the second book, the memory of Tom Riddle tells Harry:

"I decided to leave behind a diary, preserving my sixteen-year-old self in its pages, so that one day, with luck, I would be able to lead another in my footsteps, and finish Salazar Slytherin's noble work."

In the sixth book, Dumbledore explains:

"[The diary] worked as a Horcrux is supposed to work -- in other words, the fragment of soul concealed inside it was kept safe and had undoubtedly played its part in preventing the death of its owner. But there could be no doubt that Riddle really wanted the diary read, wanted the piece of his soul to inhabit or possess somebody else, so that Slytherin's monster would be unleashed again."

Consistent and helpful.

Even more interesting to me is that these passages seem to hint at why Lucius Malfoy would choose the particular moment he did to pass the diary along to a Hogwarts student after holding on to it for 50 years: he recognized the threat Harry Potter himself posed to Voldemort's return and hoped, by slipping the diary into Ginny Weasley's text book, to give whatever evil force the diary contained the chance to deal with Harry before Harry grew up and grew strong.

It had always been a puzzle to me why Lucius chose that moment to re-introduce the diary and, of course, there is at least one moment in the stories where he is questioned for that decision, for disposing of a precious piece of Voldemort's soul so carelessly. We are led to believe, by Dumbledore's own comment at the end of Book Two, that Lucius chose to give the diary to Ginny so that the Weasley family's reputation would be tarnished and Mr. Weasley's Muggle Protection Act would be thwarted.

But I think it was deeper. I think Lucius Malfoy knew, at least to an extent, what the diary contained and was acting under instructions from Voldemort to place it at Hogwarts when things seemed most opportune or when an intervention of this nature was most needed.

Malfoy saw the danger Harry posed on an on-going basis to the Dark Lord's return -- Harry had, after all, defeated Voldemort once again at the end of The Philosopher's Stone -- and decided it was time to bring his Master back to deal with that threat.

I agree. There is no way Voldemort told Lucius Malfoy about his intention to create Horcruxes, nor that the diary he was entrusting to Malfoy was a Horcrux, but he must have explained to Malfoy that the diary contained a power that could open the Chamber of Secrets and wreak havoc at the school.

That's my theory, at least, but I have to admit that I'm not one-hundred per cent convinced of it even now. What do you think?