If Hollywood gets its way, future broadcasts of digital television will not only have crisp video and sound but also invisible data to block unauthorized sharing.

The "broadcast flag" is promoted by content owners as the least intrusive way to keep consumers from illegally redistributing copyright works. Digital TV technology, they say, can finally take off once popular movies and shows can be safely broadcast without fear of Internet piracy.

But critics argue the flag is the latest attempt to wrest control from consumers, stifle innovation, create inconvenience, turn tinkerers into criminals and raise prices - all for a technology that won't stop piracy anyway.

"This has to do with controlling the customary, expected uses of law-abiding consumers in their homes," said Cory Doctorow of the Electronic Frontier Foundation. "When they say 'This keeps honest people honest,' they mean 'This keeps honest people in chains.'"

Supporters say the flag would be used to limit redistribution to "personal networks," not crack down on personal copying. For example, a recorded program could be viewed at home but not sent to millions of "friends" on the Internet.

Though the flag is unlikely to be everything Hollywood hopes for or civil libertarians fear, it is under serious consideration by industry and the government and could quickly alter the landscape of copy protection.

No longer would users be trusted to take the ethical route. Rather, anyone who strays from a content creator's desires would run into a technical roadblock.

The concept mirrors a trend in "trusted" computer chips and software. The technology is designed to keep hackers out, but can also be used to restrict everyday users.

But unlike "trusted computing" initiatives, the broadcast flag would be just a mark on the content. It could still be transmitted without encryption over the airwaves.

The flag - only a few bits of information that transmit with a broadcast - would be recognized by devices that turn the signal into a viewable format. Whether a set-top box, PC card or handheld computer, the device would follow rules triggered by the flag.

If the mark is permissive or missing, a program can be freely copied and distributed. Another variant would allow copying but restrict redistribution. It's also possible that some programming - such as pay per view - could be flagged to prevent any copying whatsoever.

To ensure the flag will be recognized, the government must require compatibility among devices that receive digital signals, from set-top TV boxes to components of general-purpose computers. Such a move, critics say, could harm high-tech innovation, because the government isn't known for speed or adaptivity.

"It's one of those things that makes us both skeptical and careful about this whole activity of getting the government involved," said Joe Tasker, general counsel of the Information Technology Association of America.

Earlier this year, the Federal Communications Commission announced it would consider setting rules after representatives from the high-tech and entertainment industries reached a general consensus on the flag. Commissioners have sought comments on whether the agency has the jurisdiction to act, as well as on the technology itself.

Even if the FCC decides it doesn't have jurisdiction, key members of Congress are standing by. After all, a big payoff is at stake once the nation's TVs can receive digital broadcasts and the airwaves that now carry analog signals can be auctioned off.

Though some, including the ITAA, suggest further study, others point out that the alternative - end-to-end encryption of TV broadcasts - would render existing digital TVs useless.

The flag "doesn't disenfranchise any consumers," said Don Whiteside, vice president of legal and government affairs at Intel, which along with Mitsubishi Digital Electronics America and News Corp.'s Fox Technology Group led the Broadcast Protection Discussion Group of 70 companies that reached the consensus on the flag.

Still, critics worry that building in a single, government-mandated type of security could stifle innovation, especially if the approved technology is proprietary and secret.

If so, open-source programmers who share code to build software like the Linux operating system could find themselves prosecuted under laws barring the cracking of copyright protection schemes.

Even with such protection, the broadcast flag won't stamp out all piracy. It can be bypassed simply by converting digital signals to analog.

But it's a strong enough deterrent against casual copying to make studios comfortable, said Fritz Attaway, executive vice president of the Motion Picture Association of America.

"It will provide some level of discouragement to uploading broadcast content to the Internet and distributing it around the world," Attaway said.

Critics of the flag say it might be used to prepare the high-tech industry to accept more governmental restrictions on technology, such as when Hollywood decides it wants to also combat analog copies.

Others question its need.

High-definition video broadcasts are simply too large to be circulated online, and laws already exist to prosecute infringement, Doctorow said.

"It addresses a nonexistent problem with an insufficient technical measure at great expense to liberty and innovation," he said.