I'll believe quantum computing exists when someone releases the factors of an RSA or DSA keypair with economic value, or at least a keypair not generated by the

I'll believe quantum computing exists when someone releases the factors of an RSA or DSA keypair with economic value, or at least a keypair not generated by the same people factoring it. Something like the code signing keys for Apple's boot ROM, or the root key of a well-trusted CA. It doesn't even have to be their current keys, it can be something older / shorter, as long as it's outside the time horizon of classical factoring.