DE-crypting calls

joerg at joerg at
Tue May 20 19:01:17 CEST 2008

Am Fr  16. Mai 2008 schrieb Al Johnson:
> On Friday 16 May 2008, ramsesoriginal wrote:
> > I was just wondering: we have seen the problems of encryptingcalls.
> > But what about decrypting them? Let*s say someone hasa method to call
> > you with some sort of encryption.. would it be possible to write a
> > decryption for it? Maybe public key?
> Depends what sort of calls you mean. If it's GSM voice calls then the same 
> problems apply as already discussed. If you're talking about a data link 
> encrypted end to end and passing voice data then it's possible, probably 
> using established standards. You could make an OpenVPN or IPsec tunnel end 
> end, then use SIP, h323 or IAX2 over it. You could use one of the secured 
> versions of SIP directly, at least one of which uses public keys, but none 
> them are universally accepted. 

What about ZRTP? (Zimmerman, PGP inventor). Have a look at! Via 
GSM you can setup not only voice calls, but also fax and *DATA* calls with up 
to 14400bps. Tunneling SIP and low bandwidth RTP/ZRTP through this link 
should be feasible with low effort

> You could even roll your own protocol using  
> TLS or something. 
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