Analog hole

Analog hole

The analog hole is a fundamental and inevitable vulnerability in copy prevention schemes for noninteractive works in digital formats which can be exploited to duplicate copy-protected works that are ultimately reproduced using analog means. Once digital information is converted to a human-perceptible (analog) form - as it must be, given the analog nature of our human senses - it is a relatively simple matter to digitally recapture that analog reproduction in an unrestricted form, thereby circumventing the restrictions placed on copyrighted digitally-distributed work. Media publishers who use digital rights management (DRM), to restrict how a work can be used, perceive the necessity to make it visible and/or audible as a "hole" in the control that DRM otherwise affords them.

The term "analog hole" was first popularized by the Motion Picture Association of America and some of its members during speeches and legislative advocacy in 2002; this term later fell into disrepute within the industry after it was abbreviated to "a. hole" (which was misconstrued as an allusion to the vulgar "asshole"), thus being replaced by analog reconversion problem, analog reconversion issue and similar terms.


Although the technology for creating digital recordings from analog sources has existed for some time, it was not necessarily viewed as a "hole" until the widespread deployment of DRM in the late 1990s. It should be pointed out that this kind of duplication is not a direct digital copy, and therefore has flaws, the magnitude of which depends on the nature of the reproduction methods used. This kind of reproduction is, in many ways, similar to the initial digitization of any analog medium or performance, with all the pitfalls and benefits of such digitization. For example, bootleg films may have poor audio, or highly washed-out video. At a minimum, copy protection can be circumvented for types of material whose value is aesthetic, and does not depend on its exact digital duplication. In general, performing a digital-to-analog conversion followed by an analog-to-digital conversion results in the addition of noise in an information-theoretic sense relative to the original digital signal. This noise can be measured and quantified. Naturally, the use of high quality conversion equipment reduces the amount of noise added, to the point where such noise is essentially imperceptible to the human senses. For instance, playing a video in a DVD player and using a DVD recorder to record the output can create a high-quality copy of the video.

Regardless of any digital or software copy control mechanisms, if music can be played on speakers, it can also be recorded, at the very least, with a microphone. And just as text can be printed or displayed, it can also be scanned and recognized, at the very least, with a camera and a screen. Because of the way modern computers load programs from random access media such as CDs and DVDs, software cannot usually be copied in this manner. However, software supplied on audio cassettes (a popular format on 1980s home computers) is not random access, and can often be copied by simply recording the cassette's analogue audio signal on another cassette, without the need for a computer or any digital equipment. In the 1980s, many European radio stations experimented with free software distribution using this method called basicode, which sounded to human listeners as several minutes of apparently random beeps. Listeners recorded the beeping part of the radio programme to cassette, and then played it back in their computers' cassette drives to load software.

In 2002 and 2003, the U.S. motion picture industry publicly discussed the possibility of legislation to "close the analog hole" — most likely through regulation of digital recording devices, limiting their ability to record analog video signals that appear to be commercial audiovisual works. These proposals are discussed in the Content Protection Status Report, Consumer Broadband and Digital Television Promotion Act, and Analog Reconversion Discussion Group. Inventors of digital watermark technologies were particularly interested in this possibility because of the prospect that recording devices could be required to screen inputs for the presence of a particular watermark (and hence, presumably, their manufacturers would need to pay a patent royalty to the watermark's inventor).

The motion picture industry has also pursued several private-sector approaches to eliminating the analog hole; these might be implemented without additional legislation.

* Analog signals can be degraded in ways that interfere with or confuse some recording devices. For example, Macrovision attempts to defeat recording by VCRs by outputting a deliberately distorted signal, crippling the automatic gain control for video, causing the brightness to fluctuate wildly. While this is only supposed to happen to copies, it may, as an inadvertent side-effect, happen when viewing the original video as well. Some vendors claim to have developed equivalent techniques for preventing recording by video capture cards in personal computers. Devices exist, however, to counteract this measure.

* Manufacturers of recording devices can be required to screen analog inputs for watermarks (or Macrovision or CGMS-A) and limit recording as a condition of private contracts. For example, a manufacturer who licenses patents or trade secrets associated with a particular DRM scheme might also be obliged as a purely contractual matter to add recording limitations to digital recording products.

* Manufacturers of certain playback devices such as set-top boxes can be required, as a condition of private contracts, to allow publishers or broadcasters to disable analog outputs entirely, or to degrade the analog output quality, when particular programming is displayed. This capability is one example of Selectable Output Control. A broadcaster could then prevent all recording of a broadcast program by indicating that compliant receiving devices should refuse to output it through analog outputs at all.

In theory, it is possible to bypass all these measures by constructing a player that creates a copy of every frame and sound it plays. Although this is not within the capability of most people, many bootleggers simply shoot at the video being displayed with a video camera or use recording and playing devices that are not designed to use the protection measures.

But by far, one of the most effective ways for a publisher to defeat analog reconversion is to make the work interactive.Analog reconversion methods can copy only signals, not the rules used to generate those signals.If the rules are such that the sequence of user input has a strong effect on the output, especially in the case of a video game, analog reconversion becomes much less feasible. Put simply, watching a recorded video of someone else playing the game is not generally regarded as being equivalent to a person playing that game for himself.

Engineering vs. business and political views

The notion of "plugging the analog hole" may be based on fundamental misconceptions of the meaning of analog and digital.There is a history of business and political desires combined with core misunderstandings of technology leading to legislation and industry practices that are counterproductive or fundamentally flawed on an engineering theory level.

One example was an early law passed by the European Parliament to support DRM in response to widespread buzz about unauthorized digital music downloads being held in computer memory caches. Apparently reasoning by analogy to "caches of arms," the use of computer memory caches was outlawed. The legislators, hearing a very general piece of computer jargon (caching) associated with infringement, banned it, not realizing it was a basic digital storage technique found in most modern equipment. A BBC article describing the controversy, itself demonstrates the difficulty of explaining to legislators and the general public the aspect that every computer and most digital devices of any kind would have to be destroyed were the law to be evenly enforced. [] Far from a specialized illegality, caching is a universally used computer memory technique, leading to comparisons of this law to the classic "urban myth" [] of the Indiana Pi Bill.

A body of opinion in the engineering community puts the buzz about the "analog hole" in the same category: an impossible strategy based on fundamental misunderstandings by people who are not engineers that will not solve the stated problem but cause expense and confusion. Both "analog to digital" and "digital to analog" conversion are such basic technologies, with so many possible implementations, that the idea of being able to block conversion by these means is unrealistic. Engineers are aware of mathematical and physical principles that often begin with "It is not possible to..." which sometimes come in direct conflict with business and political goals. One does not have to be an engineer to understand that it is simply not possible to simultaneously display and conceal a signal. In particular, an audio signal must be converted to analog before it reaches the speaker.

In addition to this general principle, theory says that digital watermarking and other restrictions on the "analog hole" can be simply defeated by a variety of well-known techniques, such as dithering.

Copyright law vs. particular techniques

Copyright law has been defined in terms of general definitions of infringement in any concrete medium. This classically focused such law on whether there is infringement, rather than focus on particular engineering techniques. Detecting infringement within the social and legal system avoids a legacy of outlawing generic, universal, popular, widespread, useful, and possibly uncontrollable engineering techniques in response to specific misuses.

Consumer vs. professional equipment

In every copy-restricted medium, there are two grades of equipment: consumer, which may include copy restriction, and professional, which by necessity, allows access in a way that is above copy restriction. In most countries, the sale of professional equipment is not regulated per se, although price alone prevents most users from getting access to it. The price may not put off piracy organisations that still regard it as a good return on investment, especially as the cost of such equipment continues to drop and as direct digital piracy becomes more difficult.

ee also

* Digital rights management
* Copy protection in Japan
* Secure cryptoprocessor
* Fritz-chip
* Trusted Computing
* Digital Transition Content Security Act
* Fair use

External links

* [ Analysis of "analog hole"]
* [ A bill introduced to close the Analog hole]
* [] A weekly Podcast about gaming and discussions about Digital Rights issues in the news as it pertains to gaming.


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