I was in the exact spot about 7 years ago; I wanted to change jobs, but after I revealed my salary I was getting a +10% offer. Until a friend told me -- NEVER, EVER, EVER reveal your current salary, either don't reveal it, or just... lie. So I figured, hey, none of these companies actually required any proof of my current salary, I won't make a written statement, so... why not. And the next time, I lied, I said my salary was 40% higher than it actually was. And that's how I got a 50% salary increase :|