Bitcoin the currency and protocol has never been attacked. I mean it is like saying I saw a 7-11 get robbed so obviously there is a critical flaw in the dollar.
My point is bitcoin doesn't exist on paper. It exists as bits inside a machine. Without that machine we cannot transact business to even write to the blockchain.
Cash can be transacted hand to hand. Bitcoin can't.
Focusing only on the math and not the machines and implementation is missing half the equation.
you just need a public key, you can print it out if you like ... anyone can go to the blockchain and say .. yep I can see you go it .. do you have a private key? then you just need to sign a message with a private key to prove that you control the bitcoins ..
And yes the system is strong because sha and elliptic curve has proved it already (not only to bitcoin, a very good implementation) but on almost any financial cryptography standers .. if you can break it... you are the most powerful man in the world ... ( you'll also be able to crack almost any traditional bank system too )