[Cryptography] Subject: OpenPGP and trust

[Arnold Reinhold]

On Sat, 29 Mar 2014 11:43 Stuart Longland wrote:
...
> I'm looking at ways in which I can authenticate users, and the automatic 
> agents they might be responsible for, in a distributed manner.  In 
> particular, I'm thinking of the amateur radio world but the situation is 
> applicable elsewhere too.
> 
> In Amateur Radio, encryption is more or less outlawed.  In the US, it's 
> not allowed on air, end of story (I hear much vigorous discussion about 
> it on the digitalvoice mailing list).  Here in Australia, it's allowed 
> for very specific circumstances, such as in emergency communications.  
> Regardless of your location, in most places it is frowned upon.
> 
> The information I'd be wanting to send isn't of a nature that requires 
> great confidentiality, so encryption in this case is pointless.  (i.e. I 
> don't care that someone sees me tell a computer to "reboot", but I do 
> mind if someone tries rebooting my computer.)  I do however, want to be 
> able to identify users and authenticate them without opening them up to 
> the risk of impersonation.
> 
> Some of these services are accessible by both radio and the Internet, and 
> while the latter permits encryption, authentication on both is a real 
> issue. ...

> Some might be able to take a password the user supplied to you and check 
> that for validity.  This is good over the Internet if you can retrieve 
> the password confidentially, but no use if encryption is unavailable.  
> Well, you can try it: but then hey, everyone else knows your password now!...

First, as I understand things, the prohibition on encryption in Amateur Radio under International Radio Regulations and US FCC regulations does not apply to authentication. They both say  "Transmissions between amateur stations ... shall not be encoded for the purpose of obscuring their meaning ..." 

The US Amateur Radio Relay League (ARRL) filed a lengthly brief with the FCC opposing a petition to allow encryption, on the grounds it was harmful and unnecessary. http://apps.fcc.gov/ecfs/document/view?id=7520928844 

Section IV of the brief specifically covers authentication, and says: "ARRL has previously advised members, following discussions with Commission Enforcement Bureau and Wireless Bureau staff, that encoding exclusively for authentication purposes does not violate Section 97.113(a)(4). The use of encryption to authenticate the identity of participants who are entitled to use Amateur Radio data networks, for example, is not intended
to obscure the meaning of a transmission. Rather, it is for the purpose of insuring control and prohibiting unauthorized access to Amateur stations and networks of stations. Therefore, encryption for purposes of authentication of a user and prevention of access by unlicensed or unauthorized persons is arguably the same as the goal of the encryption prohibition in Section 97.113(a)(4) in the first place: It allows Amateurs to police their own allocations and prevent intruders, as indeed they must do in order to maintain control of their licensed facilities."

I have no idea if the Australian authorities take the same view, but I imagine you would have a strong argument for such an interpretation.

Second, I would ask what kind of system you would set up in the good old days before electronic signatures? I imagine you might make a list of people authorized to use the facilities, a separate list of those authorized to make changes and finally a list of people authorized to issue authorization, the last perhaps the governing board or owner of the organization.  You might have reciprocal use privileges with another organization, but would expect members with change privileges in the other organization to apply for the same privileges in your group, perhaps with expedited approval. You would also want to know who in the other organization is authorized to issue credentials. 

It seems to me a similar system model could be set up using OpenPGP signatures, rather than use the more generic trust levels. 

73

Arnold Reinhold, K2PNK