Schneier on Security

Clive Robinson • March 5, 2017 6:57 AM

@ Kurt Seifried,

We can’t protect against the law in a technical manner unless we somehow give consumers more control over their devices and updates, which on the flip side means a huge pile of out of date IoT and the problems that brings us.

Actually you are wrong because you are “thinking inside the box” or more correectly the communications channel. And you are not alone in this false assumption as I’ve pointed out over the years here.

If you think back to what was done in the Victorian era and back to almost the time man first started to write you will see they had solved this problem.

To describe what a diplomat would have done to send a message back to his government keeping the contents private.

He would write his dispatch in plaintext, give it to his private secretary who would use a code book to turn the message into “codetext” this would then have been given to a cipher clerk to be “super encrypted” to produce the final “cryptotext” which would then be sent by some untrusted communications system such as the postal service or telex system.

What is clear from this is the divison of process and how the untrusted is kept issolated from the trusted. There are two basic ways the security can be breached. Firstly by obtaining the ciphertext in the communications channel and crypto-analyze it –or decipher it if key is known– back to codetext then in a similar way back to plaintext. Secondly the attacker can try to get access to the codetext or plaintext at either the diplomat’s office or at their home governments foreign office department where the messages are filed.

Most modern cipher systems at the algorithm level are thought to require too many resources for cryptanalysis on individual message or link level usage (though Diffy-Helman weakness for mass usage was just possible). Which means that cryptanalysis attacks on encrypted communications should not be possible in the communications channel. But for many this does not appear to be the case with modern systems, which is where your “Technology -v- legislation” foreboding comes from.

Which means that either there is a weakness in the system implementation –which there is– and/or the attacker has the ability to get at the plaintext –which they do– by “end-running” the message privacy protections.

The reason that both attacks work is simple, on modern systems the attacker has as much –or more– control on the supposadly trusted side of the security end point as they do in the untrusted communications channel.

That is we are stupid enough to put the security end point in a system we have no effective control over, whilst the attacker does have control. So message security is not possible in that usage configuration. That is the attacker can do a full end-run attack and get directly at the plaintext because there is no effective segregation in the likes of smart phones or other ICT that has a communications port the attacker has access to.

Thus the solution to your “Technology -v- legislation” foreboding is to put the security end point beyond the reach of the attacker… Plain and simple as the Victorians and earlier clearly understood and for some reason we appear to have forgotton.

Thus you need to consider any ICT equipment that is “connected” directly or indirectly to a communications port available by some method to an attacker as “untrusted”. You also need to ensure that you can put the security end point beyond their ability to do an “end-run”.

As a simple[1] example, you could use a paper and pencil One Time Pad encryption system to put the security end point beyond the reach of the untrusted communications channel. But you would also need to setup a place where you can use the OTP that the attacker can not end-run around by say having a small surveillance camera concealed in a ceiling mounted smoke detector, or wall mounted clock etc etc.

In essence the historical version of what became known as “air-gapping” in the latter half of the last century. However as I’ve also made clear air-gapping has been insufficient for the past couple of decades. I developed ways to cross air-gaps to show why voting machines were never going to be secure, and half a decade later Stuxnet should have made that totally clear to anybody who knows more about ICT than how to wave a mouse at an application. Which is why I now talk about the more restrictive “energy-gapping” that covers all aspects of unintentional eminations –TEMPEST– and a large majority of susceptability or “fault injection” attacks which the likes of the NSA, GCHQ and other national Signals Intelligence (SigInt) agencies developed “secure cells” which now get called Sensitive Compartmented Information Facilities or SCIFs,

https://en.m.wikipedia.org/wiki/Sensitive_Compartmented_Information_Facility

I’ve previously described on this blog what you need to do to set up both a semi-permanent cell which is in effect an extension of an EMC test “screened room”. Also a very tempory system to stop audio/visuall end-run attacks, which can assembled / disassembled in seconds from unsuspicious items you would expect to find in nearly all homes (chair, table, foldaway laundry rack, blanket/ throw, cushions, glass fronted picture/mirror, angle poise lamp, table fan, battery radio etc).

[1] By saying simple I am removing other asspects you would need to consider such as what is called “KeyMan” or the managment, secure handeling and auditing of Keying Material (KeyMat).