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An e-mail provider provides people with usernames for e-mail accounts. That normally means that they have access to your e-mail if it is unencrypted.

Likewise, do sip registrars have access to people's conversation when they voip each other? Or when you use your sip account to call a regular phone through a third party voip plan?

I also asked here the same thing about the voip providers, but the question was closed as a duplicate. It isn't a duplicate. My doubt is both about sip registrars -- those whose give you an address that looks like email -- and voip providers -- those whom you pay so you can not only make sip to sip calls but also sip to regular phones.

So the general question is: when you use sip for voip, who can listen and how to protect yourself?

share|improve this question
Slipped, just review them and accepted most, thank you. This question though I feel it's still not quite answered. – Strapakowsky Jun 15 '12 at 15:36
Excellent - let's see who else weighs in on this one. – Rory Alsop Jun 15 '12 at 16:04
up vote 4 down vote accepted

When you do a call from SIP to a regular phone line, somewhere in the middle it will exist a gateway which translates the phone call from IP network to a PSTN. So it is doable someone in the middle intercept the communication (in the IP network or PSTN), at least, to lawful interception.

Only if two SIP peers call directly is less possible the have a eavesdrop.

share|improve this answer
Of course your ISP can eavesdrop on the lot to some degree. – ewanm89 Jun 11 '12 at 20:40

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