GuardVox Phone

GuardVox Phone is a softphone which supports ZRTP protocol, offering a safe and efficient way to guarantee the security of IP telephony. ageet Corp. has been working closely together with Telesecret Corporation, a company founded by Phil Zimmermann to create encrypted voice and video communication solutions using the IETF standard ZRTP that he designed. As one of the leading experts in the security field, Phil Zimmermann has gained a reputation as an uncompromising guardian of privacy rights in a long legal battle to make his Pretty Good Privacy (PGP) email encryption protocol available to users worldwide. ageet Corp. has integrated Telesecret’s ZRTP library into GuardVox Phone, allowing it to offer secure call encryption in accordance with standards laid out by the National Institute of Standards and Technology (NIST) based on NSA guidelines. These standards certify that the applied encryption can be used to protect information up to the top secret level.

The potential risks using IP network

Saving money by using IP communications instead of the plain old telephone system (POTS) is nothing new and can be considered standard these days with over 60% of all calls being placed that way. However, few people are aware of the potential security risks that come with the switch to IP telephony. Where the POTS offered basic security due to the fact that each line had to be tapped physically in order to listen in on a conversation, IP calls can be intercepted easily using free software. While even the US government cannot wiretap more than 1% of all concurrent analog calls simultaneously, the majority of IP calls can be recorded and processed with relative ease and little cost. As the effort to do so decreases, listening in on IP communications becomes more tempting than it has ever been before. Depending on the topic of the conversation, an irreversible loss of information could have devastating consequences for businesses of all kinds, as well as government and military organizations. As going back to the old analog days to protect ourselves is not an option, the need for efficient and transparent protection against security threats such as wiretapping or even espionage is imminent.

Ultimate level of security

Other encryption solutions have tried to address the problem, but none achieves the ease of use and thorough security that GuardVox Phone with Telesecret’s ZRTP implementation offer. While some products still cater to legacy analog calls, others offer only incomplete protection for internet calls by sending vital information in plain text or necessitating a working Public Key Infrastructure (PKI). The PGP standard which is used to send encrypted email also requires a PKI, a fact that thwarted its widespread adoption and is single-handedly responsible for the fact that 99% of all E-Mails are still sent out unencrypted. Other approaches to solve the problem are expensive, proprietary hardware solutions that are not interoperable with other secure telephony solutions. The strengths of the GuardVox ZRTP solution become obvious: it requires no PKI, can be adopted on many platforms and uses an open standard for encrypted calls. ZRTP is a peer-to-peer protocol that does not require a central server or PKI to establish a secure call. Endpoints exchange the keys to encrypt a call with the security status being displayed at all stages. End users then compare a Short Authentication String (SAS) to make sure that there is no man-in-the-middle (MiTM) listening in on the call. This human element in the verification process is unique to ZRTP and further raises its security and transparency. The key exchange itself takes place using either the state of the art Diffie-Hellman (DH) or military grade Elliptic Curve Diffie-Hellmann (ECDH) protocol. The call’s audio stream is encrypted using the strong Advanced Encryption Standard (AES).

Why ZRTP?

Diagram 1　Potential VPN security issues

VPN is well known as a network that uses a public telecommunication infrastructure, such as the Internet, to provide remote offices or individual users with secure access to their organization's network. It aims to avoid an expensive system of owned or leased lines that can only be used by one organization. The goal of a VPN is to provide the organization with the same, secure capabilities, but at a much lower cost. However, do you aware there is potential problem exist if the VPN gateways are configured incorrectly? As shown on Diagram 1, if Department A holds PKI1 and C holds PKI2, the connection will not be secured due to the mismatch of PKIs. Also, though Department A and B holds same PKIs, since Department B uses wireless between the router and the user's softphone/smart phone,  it is fairly easy for the attacker to eavesdrop the wireless LAN and decode the connection.  Moreover, if this connection has used WEP encryption only then the security will even get lower.

Diagram 2　ZRTP Security

ZRTP is a peer-to-peer protocol that does not require a central server or PKI to establish a secure call. Endpoints exchange the keys to encrypt a call with the security status being displayed at all stages. End users then compare a Short Authentication String (SAS) to make sure that there is no man-in-the-middle (MiTM) listening in on the call. This human element in the verification process is unique to ZRTP and further raises its security and transparency. The key exchange itself takes place using either the state of the art Diffie-Hellman (DH) or military grade Elliptic Curve Diffie-Hellmann (ECDH) protocol. The call’s audio stream is encrypted using the strong Advanced Encryption Standard (AES).

What is "self-healing" feature?

The key continuity features of ZRTP are analogous to those provided by SSH, but they differ in one respect. SSH caches public signature keys that never change, and uses a permanent private signature key that must be guarded from disclosure. If someone steals your SSH private signature key, they can impersonate you in all future sessions and mount a successful man-in-the-middle (MiTM) attack any time they want. ZRTP caches symmetric key material that is mixed into the next session's secret session key, which changes with each session. If someone steals your ZRTP shared secret cache, they only get one chance to mount a MiTM attack, in the very next session. If they miss that chance, the retained shared secret is refreshed with a new value, and the window of vulnerability heals itself, which means they are locked out of any future opportunities to mount a MiTM attack. This gives ZRTP a "self-healing" feature if any cached key material is compromised. A MiTM attacker must always be in the media path. This presents operational difficulties for the attacker in many VoIP usage scenarios, because being in the media path for every call is often harder than being in the signaling path. This creates coverage gaps in the attacker's opportunities to mount a MiTM attack. ZRTP's self-healing key continuity features are better than SSH at exploiting any temporary gaps in MiTM attack coverage. Thus, ZRTP quickly recovers from any disclosure of cached key material.  

Phil Zimmermann

Philip R. Zimmermann is the creator of Pretty Good Privacy, an email encryption software package. Before founding PGP Inc, Zimmermann was a software engineer with more than 20 years of experience, specializing in cryptography and data security, data communications, and real-time embedded systems. Zimmermann currently is consulting for a number of companies and industry organizations on matters cryptographic, and is also a Fellow at the Stanford Law School's Center for Internet and Society. Zimmermann has received numerous technical and humanitarian awards for his pioneering work in cryptography. In 2003 he was included on the Heinz Nixdorf Museums Forum Wall of Fame, and in 2001 he was inducted into the CRN Industry Hall of Fame. In 2000 InfoWorld named him one of the Top 10 Innovators in E-business.

Visit Zimmerman’s website for further information (external link).

Highlights

	Audio encryption The call’s audio stream is encrypted using the strong Advanced Encryption Standard (AES). This is very difficult for attacker to decrypt and leads user to establish safe connection.
	Self healing feature ZRTP caches symmetric key material that is mixed into the next session's secret session key, which changes with each session. If someone steals your ZRTP shared secret cache, they only get one chance to mount a MiTM attack, in the very next session. If they miss that chance, the retained shared secret is refreshed with a new value, and the window of vulnerability heals itself, which means they are locked out of any future opportunities to mount a MiTM attack. This gives ZRTP a "self-healing" feature if any cached key material is compromised.
	Military grade Elliptic Curve Diffie-Hellmann (ECDH) protocol is supported. The key exchange could be done using either the state of the art Diffie-Hellman (DH 2048bit) or military grade Elliptic Curve Diffie-Hellmann (ECDH 384bit) protocol on your demand. The Payload also can be selected between AES128bit or AES256bit.
	Security confirmation pop up Some solution would not show or requires complicated procedure to confirm whether the call is safe or not but GuardVox Phone will detect if the call is safe  and notify the user with window pop up.
	Simple authentication string The window pop up will not display once the "Verify" button has been clicked, this feature becomes very useful if the user prefer not to have the window pop up to be shown on every call. To check the security once in a while also available by doing it manually even after verification.

Detailed Specifications

Features
High quality sound, low delay buffering UPnP, STUN Support Answering Machine Click to Call Function Wideband codec DND (Do not Disturb) Function VAD (Voice Activity Detection) bidirectional noise cancellation Call History Self healing feature Security confirmation pop up	Number Auto Complete Address Book, Outlook Support Speed Dial Function Inband/RFC2833 DTMF send Multiple Codecs※ IPv6 support Calling Rules Incoming call notifications Audio encryption Military grade ECDH protocol is supported Simple authentication string * G.711u / G.711a / GSM-FR / Speex Narrowband / Speex Wideband
System Requirements  OS Windows XP / Vista / 7   CPU x86 800 MHz (1.6 GHz recommended) Memory 512MB (1 GB recommended) HDD 20 MB for program files Connection Up- and Downstream of each 80 kbps or above Other Speakers and microphone; headset or handset