[Cryptography] Regulations of Tempest protections of buildings

[Bill Frantz]

On 4/10/17 at 2:31 PM, iang at iang.org (iang) wrote:

>Like Ham radio operators yelling at you if you start using crypto...

In the US, and I suspect almost everywhere else, it is illegal 
to attempt to hide the meaning of communications via ham radio. 
(There's an exception for controlling a satellite.) All of the 
codes used by hams (e.g. the Q codes) are published, the data 
encoding techniques are also published, and cyphers aren't used. 
Hams generally want to be seen by government regulators as being 
good actors as a way of protecting the spectrum allocations they 
have. Hence bristling when you start using crypt.

As an aside, I think we are safer if people with scanners can 
understand police radio communication than if these 
communications are encrypted, as is becoming more common.

As I read the regulations, crypto can be used for 
authentication. There are a number of applications where this 
would actually be useful, including limiting control of 
repeaters to authorized people. In this application, replay 
prevention is the biggest problem.

When I was working on the E communication protocol, the US 
government was trying like mad to suppress the legal use of 
crypto for secrecy. I looked at what it would take to yank the 
secrecy while keeping the authentication, and it turned out to 
be a hard problem. The tokens the E runtime passed between 
machines to identify remote objects needed to be kept secret. I 
think the problem could have been solved, but I am very glad I 
didn't have to solve it.

Cheers - Bill

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