Bitcoin is a crypto-currency, cash controlled by mathematics instead of greedy bankers.
I get what you're saying, but I don't think the layman wants their cash controlled by mathematicians either. Nor does the layman want the burden of learning what a crypto-currency might be. How about:
Bitcoin is a currency controlled by
you instead of by a greedy wunch of bankers.
Not mathematicians! Mathematics. I would especially like to think most would want their currency controlled by mathematics. It's well proved and trustworthy when it comes to numbers. ;)
More and more people (even not computer savy) are learning about cipherspace. Why not crypto-currencies? Didn't say it would work this week, but people learn new terms all the time.:) For now it could be skipped though, for one tagline.
Bitcoin is a Internet-based currency, controlled by the rules of mathematics instead of greedy bankers.