Although two other specifications also were proposed, experts expect that the one proposed by the five leading companies is likely to become the defacto industry standard (See chart.).

It was not easy nor smooth for the five companies to come to an agreement.

When the Digital Transmission Discussion Group (DTDG) started publicly accepting applications in April 1997, a total of eight firms, including PictureTel Corp., NDS and Texas Instruments Inc. of the United States, applied with eight different specifications. The four U.S. manufacturers insisted on adoption of the public key algorithm, while the four Japanese makers proposed for use of the common key algorithm.

It was not a coincidence that the two different key algorithms were proposed by the two countries.

The Japanese firms all are makers of home electric appliances, and hoped to incorporate the technology in their products. They expect the hardware to prevent the copying to be as simple and inexpensive as possible, with an aim to sell low-priced products.

The U.S. manufacturers, most of which are IC makers, opted for a more heavily burdened method to sell more advanced ICs.

The U.S. camp argued that users of the common key algorithm will be seriously harmed if the key is stolen. But the Japanese group insisted that the technology will not be for preventing piracy for commercial purposes. It will be no problem as far as general consumers refrain from copying digital contents without being aware of the illegality of the act, they said.

Toshiba Decision Helps Settle the Dispute

Toshiba decided to help settle the bogged down negotiations between the two camps. In August 1997, Toshiba gave up on the common key algorithm for the public key algorithm. It decided to make a joint proposal with Intel.

"We just wanted to avoid friction between U.S. and Japanese companies," said Hisashi Yamada, chief fellow of technology in Toshiba's Storage Media Business Group.

"Toshiba is a home electric appliance maker, but at the same time, it is also a personal computer maker. We feel it is not a wise policy for us to antagonize Intel. As for the issue of the number of circuits, we thought that semiconductor technologies will settle the issue anyway," he said.

In response to the move, the remaining three Japanese makers agreed to make a joint proposal in October 1997. At this point, the initial eight proposals were reduced to four, suggesting a major battle between the Intel-Toshiba alliance and the three Japanese makers.

The Japanese camp still could not make a decision by early 1998. As a result, the two camps settled on a compromise plan. In reality, it was the Japanese camp which finally backed down.

The common key algorithm was adopted only for recording equipment. A majority of equipment, such as set-top boxes, televisions and PCs, employs the public key algorithm.

The technology to prevent illegal copying requires a large number of circuits. The common key algorithm requires 5,000-8,000 gates, while the public key algorithm needs 10,000-20,000 gates. It is an increase of 400-1,000 percent from the initial plan of 1,000 gates.

The microchip production technology by 0.35- or 0.5-micronmeter design rule, which costs a lot, will still be mainstream in the next few years. But some observers think that makers can cut their costs by reducing the area of a microchip if they manufacture a microchip with the 0.25-micron meter design rule.

However, the Japanese camp opted for the compromise in fear of a delay in releasing products due to the failure in unifying the specification plans.

Two-bit Copy Control Information

The technology to prevent illegal copying uses the Copy Control Information (CCI). With CCI, digital contents providers can select one of four 2-bit information types: (1) Copy Free, (2) Copy Once, (3) No More Copies, and (4) Copy Never.

Equipment is expected to authenticate before transmitting data, if the receiving equipment has the technology to prevent copying of digital contents. The authentication should be carried out using either full authentication or restricted authentication.

Full authentication will be provided if both transmitting and receiving equipment have the public key. With this authentication, users can transfer all contents including those not allowed to be copied.

Under restricted authentication, users are not allowed to transmit contents on which copying is banned.

After the authentication, the digital contents are encrypted in real time and transferred. The algorithm for the encryption will be decided either on the revised Blowfish method or the M6 method developed by Hitachi.

Unified Specification to Promote Digital Market

The introduction of the unified specification to prevent illegal copying is expected to promote the digital equipment market. Manufacturers expect to record contents for digital broadcasting, such as terrestrial wave and cable television, on digital video tape recorders using the D-VHS method by the end of the year. The output terminal in compliance with IEEE1394 has a large potential market, since it also can serve as an input/output terminal for other services, including data broadcasting.

The move also is expected to increase the number of DVD titles. Currently, it is difficult for general users to copy videos generated on a DVD player on other recording media. That is because the current DVD players do not have an output terminal, and they have a capability to prevent illegal copying called Content Scrambling System.

However, the new move will enable makers to control transmission and receipt of data even though DVD players are equipped with a digital output terminal. Even film companies, which are very concerned about illegal copying, may release DVD titles in the future.

Chart: Detailed History of Technical Possibilities Examined by DTDG

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(Nikkei Electronics)