You're right, that's the critical question. SVM on a picture of the note would be useless against all but the 12 year olds with paper and scissors. There's no reason to believe that the differentiating features from next years' printers would be separated by the same support vectors.
I think the real security is still in features that require expensive equipment to duplicate. Is it really that hard to use cheapo photodetectors to verify differential transmission/reflection (watermark), angle-dependent coloration (hologram), or to do some primitive spectroscopy (UV even) with a plastic lens and $10 CCD?
SVM might be a easy way to aggregate the features, but in that case it's just a calibration method and doesn't give any indication of the underlying security.
And this is where you're wrong. Most detectors use a PIN diode or a phototransistor. Both work just fine with the SVM.
Again, the security given in these detectors is SO good that even if I were to give you complete knowledge of the system, you can't beat them. I can't admit to having made counterfeits, but I can say that I've seen _all_ of them, and they do not work.
No, you haven't seen them all. That's a silly claim. And if the detector is what you say, I'm about 80% sure I know both why it worked so well and how to defeat it.
As much as I wish I could make a bet with you and test this, I wish for trouble from the secret service even less, so I guess that's off the table.
I will tell you, with full knowledge of how they work, I am incapable of beating the machines for US bills. Some other currencies have better and worse protection (generally better), but I _know_ I cannot beat the machines in the US.
Also, BTW, UV doesn't work on banknotes. If you wash a banknote with detergent, the paper absorbs the UV frequency bending stuff in modern detergents and corrupts the note. However, your thinking isn't far off.
What sort of features?