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Encryption of voice traffic across the public switched telephone network (PSTN) has always been of interest to a limited number of people, mainly government agencies. Specialized systems - usually customized black boxes - have been available since the 1970s for such applications.

Shrink-wrapped systems available on a near plug-in-and-use basis, however, have been few and far between. The last system this writer came across was a £850 ($1,300) system that was marketed in the early 1990s by Cellnet on its analogue cellular (TACS) network, routing calls via Cellnet's Manchester (U.K.) electronic mobile exchange (EMX).

Unfortunately, Cellnet surcharged the calls routed via its network, which meant the system was an expensive option. Added to the fact that the system only encrypted the analogue cellular side of the connection, and not the subsequent PSTN link, it was no surprise that the service simply faded away.

Against this backdrop, CopyTele's Cryptele USS-900 encryption unit is an intriguing system. Users get a modem-style black box with rear DC power-input and phone (RJ-11) in and out sockets, as well as a ninepin RS232 socket. The front of the unit has two lamps - clear and secure - and a red touch-pad switch to toggle between the two modes. Inside the unit is a Harris Citadel CCX proprietary encryption chipset that utilizes a unique 128-bit session key on each encryption. In use it allows encryption of voice, fax and PC-to-PC communications on a controllable basis.

Installing the unit is a relatively easy task, and it may be used out of the box for encrypting voice and fax traffic. PC connections, though, require the use of the Partner software, which is supplied on CD-ROM. The disk also includes an operator's manual, a quick guide and detailing installation instructions. It is also possible to flash upgrade the unit when hooked up to a PC using the latest version of the driver software.

The USS-900 works well, and communicates over the PSTN with a similar device at the other end. All communications are either streamed through the unit on a transparent basis or, when encryption is engaged using the touch-pad (both ends of the link must engage within a few seconds of each other) the proprietary encryption kicks in seamlessly.

As the encryption system is proprietary, though, Harris Corporation won't say how it works. Our analysis, however, suggests that the analogue voice channel - either human voice or the 300/9600bps simplex fax transmissions - is encrypted and superimposed on a modem sub-carrier that transmits to the other end of the PSTN connection. Where PC-to-PC communications are involved, the devices function as encrypted PSTN modems, again using the Harris Citadel chipset to encrypt the data stream.

Along with its many other features, the USS-900 is also billed as able to protect users from viruses in its PC-to-PC connection mode, although the anti-virus system also appears to be proprietary in nature.

The user configuration of the device is minimal, however. It's not possible, for example, to alter the encryption keys on the device - a basic feature of many PC encryption products. There are two ways of looking at this issue: on the one hand, the USS-900 is 'idiot-proof' and is therefore as easy to use in the field as a conventional standalone modem; on the other hand, one could accuse the supplier of creating a simplistic solution to the perennial PSTN eavesdropping problem.

CopyTele says that the USS-900 is unique in the marketplace. While this may be true, it's difficult to see what problem the unit is aiming to solve - 10 years ago, this device would have been selling like hot cakes. These days, however, communications have moved on from vanilla voice and fax communications. Email systems now support encryption drop-ins as a matter of course, and there are several reliable encryption drop-ins for products such as Microsoft Outlook.

One example of this is Pretty Good Privacy (PGP), the public key encryption system developed by Phil Zimmerman and later sold on via Network Associates. Zimmerman also invented an Internet telephony package called PGPFone, which is found in various commercial and non-commercial editions on the Internet. Essentially the PGPFone package performs like Net2Phone and other PC-to-PC Net telephony applications, allowing encrypted communications between two PC users, making use of their machine's speakers and microphone. PGPFone is low cost and performs well, working to triple-DES, CAST and Blowfish encryption standards.

Against this backdrop, the Cryptele USS-900 is a rigid solution chasing a limited number of applications. Five years ago, corporations would have taken this solution and been prepared to pay the required $750 to $995 price tag. These days, this writer is not so sure.

The problem with the USS-900 is that in order to use its facilities users must communicate with other USS-900 users on a point-to-point basis - and, within a company, that can get expensive. If users want to use the device on a conference call basis, then that is fine, but encryption add-ons already exist for telephone conferencing systems. In addition, if your organization is getting into teleconferencing to that depth, then an Internet telephony application - such as PGPFone - is an easy and low-cost answer to the problem of eavesdropping. CopyTele says that the USS-900 has been approved for export by the US Department of Commerce. Over the last 12 months, however, so have a number of other high-power encryption hardware and software-based systems.

At the end of the day, the USS-900 is a well-equipped device for a limited number of standalone applications. Most potential users will, however, find that a PC-based application or an encrypted audio-conferencing system may be more appropriate.

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