Knuckletop Computing: The Java Ring

Aside from the different Smart Cards, a number of various devices powered by the Java Card has been introduced. Some of them have a form factor that is aimed to support a more rugged environment than traditional plastic cards.

One of the first impressive devices powered by the Java Card technology came in the form  of now famous Java Rings at the  Sun's JavaOne conference, in March 1998. The rings were issued to the conference attendees when they picked up their materials at registration. With one of these rings a user could communicate with the computers at the Hackers' Lab, help build a large fractal image at the show, or even get a cup of  their favorite coffee.

Inside the Java Ring - Java iButton

The Java Ring is an extremely secure Java-powered electronic token with a continuously running, unalterable real-time clock and rugged packaging, suitable for many applications. The jewel of the Java Ring is the Java iButton -- a  16 mm one-million transistor, single-chip trusted microcomputer with a Java virtual machine (JVM) housed in a rugged and secure stainless-steel case. Designed to be fully compatible with the Java Card 2.0 standard  the processor features a high-speed 1024-bit modular exponentiator for RSA encryption, large RAM and ROM memory capacity, and an unalterable real-time clock. The packaged module has only a single electrical contact and a ground return, conforming to the specifications of the Dallas Semiconductor 1-Wire bus. Lithium-backed non-volatile SRAM offers high read/write speed and unparalleled tamper resistance through near-instantaneous clearing of all memory when tempering is detected, a feature known as rapid zeroization. Data integrity and clock function are maintained for more than 10 years. The 16-millimeter diameter stainless steel enclosure accommodates the larger chip sizes needed for up to 128 kilobytes of high-speed nonvolatile static RAM. The small and rugged packaging of the module allows it to attach to various accessories (key fob, wallet, watch, necklace,  bracelet, etc.)

With a 32-kilobyte Java Card Environment (JCE) and I/O subsystem in mask-programmed ROM, a continuously running true-time clock, and 6 kilobytes of NVRAM memory with expansion potential up to 128 kilobytes, the Java iButton supports a true Java stack, full-length 32-bit Java integers, and garbage collection. This feature mix provides support for relatively high-end Java applets with substantial computing requirements. While the Java iButton can support the commerce models that have traditionally been the province of credit cards, its greatest promise appears to lie in its capacity to interact with Internet applications to support strong remote authentication and remotely authorized financial transactions. The use of Java promotes compatibility with these applications by providing a common language for all application programming.

Layout of the iButton Structure

Information is transferred between iButton and a PC with a momentary contact, at  up to 142K bits per second. To do that one presses iButton to the Blue Dot receptor, a $15 pipeline into PC. The Blue Dot sticks to any convenient spot on the front of a PC and is cabled to the serial or parallel port in the back.

According to the Dallas Superconductor's information, over  41 million iButtons are currently in circulation. List of the major users include the U.S. Post Office, entire truck fleet fitted with iButtons that track vehicle maintenance; Citizens of Istanbul, Turkey,  who store digital cash in the iButton, using the device as a small change purse on their mass transit system. it was also said that the U.S. Postal service has approved the cryptographic iButton as a Postal Security Device to be used in its PC Postage program that allows individuals to download postage off the Internet and print it from their own printers.