What? We all know that book was published in 1984. 20 years later doesn't count as an "earlier confirmed source".
What's proven is that by 1963, people were writing "hacker" to mean "security breaker". To insist this is a perversion is rather silly when the "perversion" occurs so early and is in fact the earliest citation.
It seems likely the two usages are coeval. The benign one is how hackers saw themselves and the malicious one is how they were perceived by authorities.
