DE-crypting calls

[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 to 
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 of 
them are universally accepted. You could even roll your own protocol using 
TLS or something.