I skimmed the start of the paper. If I have this right:
- Essentially all the currently-deployed web servers and modern browsers have the new, much better, encryption.
- Many current web servers and modern browsers support talking to legacy counterparts that only have the older, "export-grade", crypto, which this attack breaks handily.
- Such a server/browser pair can be convinced, by a man-in-the-middle who can modify traffic (or perhaps an eavesdropper-in-the-middle who can also inject forged packets) to agree to use the broken crypto - each being fooled into thinking the broken legacy method is the best that's available.
- When this happens, the browser doesn't mention it - and indicates the connection is secure.
Then they go on to comment that the characteristics of the NSA programs leaked by Snowden look like the NSA already had the paper's crack, or an equivalent, and have been using it regularly for years.
But, with a browser and a web server capable of better encryption technologies, forcing them down to export-grade LEAKS INFORMATION TO THEM that they're being monitored.
So IMHO, rather than JUST disabling the weak crypto, a nice browser feature would be the option for it to pretend it is unpatched and fooled, but put up a BIG, OBVIOUS, indication (like a watermark overlay) that the attack is happening (or it connected to an ancient, vulnerable, server):
- If only a handful of web sites trip the alarm, either they're using obsolete servers that need upgrading, or their traffic is being monitored by NSA or other spooks.
- If essentially ALL web sites trip the alarm, the browser user is being monitored by the NSA or other spooks.
The "tap detector" of fictional spy adventures becomes real, at least against this attack.
With this feature, a user under surveillance - by his country's spooks or internal security apparatus, other countries' spooks, identity thieves, corporate espionage operations, or what-have-you, could know he's being monitored, keep quiet about it, lie low for a while and/or find other channels for communication, appear to be squeaky-clean, and waste the tapper's time and resources for months.
Meanwhile, the NSA, or any other spy operation with this capability, would risk exposure to the surveilled time it uses it. A "silent alarm" when this capability is used could do more to rein in improper general surveillance than any amount of legislation and court decisions.
With open source browsers it should be possible to write a plugin to do this. So we need not wait for the browser maintainers to "fix the problem", and government interference with browser providers will fail. This can be done by ANYBODY with the tech savvy to build such a plugin. (Then, if they distribute it, we get into another spy-vs-spy game of "is this plugin really that function, or a sucker trap that does tapping while it purports to detect tapping?" Oops! The source is open...)