Aiming to provide its users with the highest possible security, MyHealthChannel.com has become the first U.S. customer of the ComDot, a chip-based credit card that uses sound waves to identify its users.

To gain access to the health site, which stores one's medical history and offers advice, users simply squeeze the dot on their ID card into the microphone of their computer. The service, supplied by ComSense Technologies Ltd., a company started by veterans of the Israeli armed forces, then transmits the information to the ComSense server. The server matches it with a name and password to authenticate the user.

Each card contains a battery, a microprocessor, a speaker, and a 3-DES (Data Encryption Standard) scheme that changes the frequency of the sound wave after each use, so the site remains secure even if an eavesdropper tapes the sound. The batteries are designed to last through 10,000 squeezes. Says ComSense senior business development director Eitan Einwohner, "If you use it 10 times a day, it will last two and a half years."