Media corporations have always used the term copy protection, but critics argue that the term tends to sway the public into identifying with the publishers, who favor restriction technologies, rather than with the users. Copy prevention and copy control may be more neutral terms. "Copy protection" is a misnomer for some systems, because any number of copies can be made from an original and all of these copies will work, but only in one computer, or only with one dongle, or only with another device that cannot be easily copied.
The term is also often related to and/or confused with the concept of digital rights management. Digital rights management is a more general term because it includes all sorts of management of works, including copy restrictions. Copy protection may include measures that are not digital. A more likely description to this is "technical protection measures" (TPM), which is often defined as the use of technological tools in order to restrict the use and/or access to a work.
In the absence of copy protection, many media formats are easy to copy in their entirety using a machine (as opposed to photocopying each page of a book). This results in a situation where consumers can easily make copies of the items to give to their friends, a practice known as "casual copying". Copy protection is most commonly found on videotapes, DVDs, computer software discs, video game discs and cartridges, and some audio CDs.
Companies that choose to publish works under copy protection do so because they believe that the added expense of implementing the copy protection will be offset by even greater increases in revenue by creating a greater scarcity of casually copied media.
Opponents of copy protection argue that people who obtain free copies only use what they can get for free, and would not purchase their own copy if they were unable to obtain a free copy. Some even argue that it increases profit; people who receive a free copy of a music CD may then go and buy more of that band's music, which they would not have done otherwise.
Some publishers have avoided copy-protecting their products, on the theory that the resulting inconvenience to their users outweighs any benefit of frustrating "casual copying".
It is worth noting that from the perspective of the end user, copy protection is always a cost. In practice DRM and license managers sometimes fail, are inconvenient to use, and do not afford the user all of the legal use of the product they have purchased.
The term copy protection refers to the technology used to attempt to frustrate copying, and not to the legal remedies available to publishers or authors whose copyrights are violated. Software usage models evolve beyond node locking to floating licenses (where up to N licenses can be concurrently used across an enterprise), grid computing (where multiple computers function as one unit and so use a common license) and electronic licensing (where features can be purchased and activated online). The term license management refers to broad platforms which enable the specification, enforcement and tracking of software licenses. To safeguard copy protection and license management technologies themselves against tampering and hacking, software anti-tamper methods are used.
From a technical standpoint, it would seem theoretically impossible to completely prevent users from making copies of the media they purchase, as long as a "writer" is available that can write to blank media. The basic technical fact is that all types of media require a "player"—a CD player, DVD player, videotape player, computer, or video game console. The player has to be able to read the media in order to display it to a human. In turn, then, logically, a player could be built that first reads the media, and then writes out an exact copy of what was read, to the same type of media, or perhaps to some other format, such as a file on a hard disk. If to another disk, then the result is a carbon copy of the copy protected disc.
At a minimum, digital copy protection of non-interactive works is subject to the analog hole: regardless of any digital restrictions, if music can be heard by the human ear, it can also be recorded (at the very least, with a microphone and tape recorder); if a movie can be viewed by the human eye, it can also be recorded (at the very least, with a video camera and recorder). In practice, almost-perfect copies can typically be made by tapping into the analog output of a player (e.g. the speaker output or headphone jacks) and, once redigitized into an unprotected form, duplicated indefinitely. Copying text-based content in this way is more tedious, but the same principle applies: if it can be printed or displayed, it can also be scanned and OCRed. With basic software and some patience, these techniques can be applied by a typical computer-literate user.
Since these basic technical facts exist, it follows that a determined individual will definitely succeed in copying any media, given enough time and resources. Media publishers understand this; copy protection is not intended to stop professional operations involved in the unauthorized mass duplication of media, but rather to stop "casual copying".
Copying of information goods which are downloaded (rather than being mass-duplicated as with physical media) can be inexpensively customized for each download, and thus restricted more effectively. They can be encrypted in a fashion which is unique for each user's computer, and the decryption system can be made tamper-resistant (see also traitor tracing).
Copy protection for early home computer software, especially for games, started a long cat-and-mouse struggle between publishers and crackers. These were (and are) programmers who as a hobby would defeat copy protection on software, add their alias to the title screen, and then distribute the cracked product to the network of warez BBSes or Internet sites that specialized in distributing unauthorized copies of software.
Software copy protection schemes for early computers such as the Apple II and Commodore 64 computers were extremely varied and creative because most of the floppy disk reading and writing was controlled by software, not by hardware. The first copy protection was for cassette tapes and consisted of a loader at the beginning of the tape, which read a specially formatted section which followed.
The first protection of floppy disks consisted of changing the address marks, bit slip marks, data marks, or end of data marks for each sector. For example, Apple’s standard sector markings were:
D5 AA 96 for the address mark. That was followed by track, sector, and checksum.
DE AA EB concluded the address header with what are known as bit slip marks.
D5 AA AD was used for the data mark and the end of data mark was another DE AA EB.
Changing any of these marks required changing the software which read the floppy disk, but produced a disk that could not be copied. Some systems used complicated systems that changed the marks by track or even within a track.
By 1980 the first nibble copier, Locksmith, was introduced. These copiers reproduced copy protected floppy disks an entire track at a time, ignoring how the sectors were marked. This was harder to do than it sounds, because Apple disks did not use the index hole to mark the start of a track. Tracks could start anywhere. Nevertheless, Locksmith copied Apple II disks by taking advantage of the sync fields between sectors, which consisted of a long string of FF (hex) bytes between each sector. It found the longest string of FFs, which occurred between the last and first sectors on each track, and began writing the track in the middle of that.
Ironically, Locksmith would not copy itself. The first Locksmith measured the distance between sector 1 of each track. Copy protection engineers quickly figured out what Locksmith was doing and began to use the same technique to defeat it. Locksmith countered by introducing the ability to reproduce track alignment and prevented itself from being copied by embedding a special sequence of nibbles, that if found, would stop the copy process. Henry Roberts (CTO of Nalpeiron), a graduate student in computer science at the University of South Carolina reverse engineered Locksmith, found the sequence and distributed the information to some of the 7 or 8 people producing copy protection at the time.
For some time, Locksmith continued to defeat virtually all of the copy protection systems in existence. The next advance came from Henry Roberts thesis on software copy protection, which devised a way of replacing Apple’s sync field of FFs, with random appearing patterns of bytes. Because the graduate student had frequent copy protection discussions with Apple’s copy protection engineer, Apple developed a copy protection system which made use of this technique.
Henry Roberts then wrote a competitive program to Locksmith, Back It UP. He devised several methods for defeating that, and ultimately a method was devised for reading self sync fields directly, regardless of what nibbles they contained.
The back and forth struggle between copy protection engineers and nibble copiers continued until the Apple II became obsolete and was replaced by the IBM PC and its clones.
Floppy disks were replaced by CDs as the preferred method of distribution, and companies like Macrovision and Sony providing copy protection schemes that work by writing data to places on the CD-ROM where a CD-R drive cannot normally write. Such a scheme has been used for the Sony PlayStation and cannot be circumvented easily without the use of a modchip.
For software publishers, a less expensive method of copy protection is to write the software so that it requires some evidence from the user that they have actually purchased the software, usually by asking a question that only a user with a software manual could answer (for example, "What is the 4th word on the 6th line of page 37?"). This approach can be defeated by users who have the patience to copy the manual with a photocopier, and it also suffers from the fact that once crackers circumvent the copy protection on a piece of software, the resulting cracked product is more convenient than the original software, creating a disincentive to buying an original. As a result, user-interactive copy protection of this kind has mostly disappeared.
Other software copy protection techniques include:
Copy protection methods usually tie the installed software to a specific machine by involving some unique feature of the machine. Some machines have a serial number in ROM, while others do not, and so some other metric, such as the date and time (to the second) of initialisation of the hard disk can be used. On machines with Ethernet cards, the MAC address, which is unique and factory-assigned, is a popular surrogate for a machine serial number; however, this address is programmable on modern cards.
These schemes have all been criticized for causing problems for validly licensed users who upgrade to a new machine, or have to reinstall the software after reinitialising their hard disk. Some Internet product activation products can allow replacement copies to be issued to registered users or multiple copies to the same license.
Like all software, copy-protection software sometimes contains bugs, whose effect may be to deny access to validly licensed users. Most copy protection schemes are easy to crack, and the resulting cracked software is then more valuable than the uncracked version, because users can make additional copies.
In his 1976 Open Letter to Hobbyists, Bill Gates complained that "most of you steal your software." However, Gates initially rejected copy protection and said "It just gets in the way."
There is also the tool of software blacklisting that is used to enhance certain copy protection schemes.
During the 1980s and 1990s, computer games sold on audio cassette and floppy disks were sometimes protected with a user-interactive method that demanded the user to have the original package or a part of it, usually the manual. Copy protection was activated not at installation but every time the game was executed.
Sometimes the copy protection code was needed not at launch, but at a later point in the game. This helped the gamer to experience the game (e.g. as a demonstration) and perhaps could convince him to buy it by the time the copy protection point was reached.
Several imaginative and creative methods have been employed, in order to be both fun and hard to copy. These include:
When Sega's Dreamcast was released 9 September 1999, it came with a newer disc format, called the GD-ROM. Using a modified CD player, one could access the game functionality. Using a special swap method could allow reading a GD-ROM game through a CD-ROM just using common MIL-CD (standard CD Boot loading, commonly found on Windows Installation Discs, Linux Live CDs, and others). Sega Dreamcasts sold after October 2000 contain a newer firmware update, not allowing MIL-CD boot.
The Microsoft Xbox, has a specific function: Non-booting or non-reading from CDs and DVD-Rs as a method of game copy protection. Also, the Xbox is said to use a different DVD file system (instead of UDF). It has been theorized that the discs have a second partition that is read from the outside in (opposite current standards thus making the second partition unreadable in PC DVD drives) which give the tracks the appearance that the disc was spun backwards during manufacture. This format (and the aforementioned hardware lockouts) appears to have been inherited by its successor, the Xbox 360.
The PlayStation 2 has a map file that contains all of the exact positions and file size info of the CD in it. It is stored at a position that is beyond the file limit. The game directly calls the position at where the map file is supposed to be. This means that if the file is moved inside the limit, it's useless since the game is looking outside the limit for it. And it will not work outside of the limit, thus making any copied disc unusable without a mod chip.
Nintendo's Wii and GameCube have their own specialty format for copy protection. It is based on DVD/miniDVD (Game Cube) technology; there is a barcode on the edge of the disc. It is not readable on standard DVD-ROM Drives, although some have been able to accomplish this using a certain specific DVD-ROM drive's "debug mode."
The PSP uses the Universal Media Disc, a media format similar to a MiniDisc. It holds about 1.2 GB. Although it cannot be copied, one can make an ISO image and play it on custom firmware using a third-party utility.
The PlayStation 3 uses Blu-ray BD-ROM discs. In addition to any protection provided by the console itself, the BD-ROM format's specification allows for a ROM-Mark which cannot be duplicated by consumer-level recorders.
Companies like Macrovision provide schemes to videotape publishers making copies unusable if they were created with a normal VCR. All major videotape duplicators license Macrovision or similar technologies to copy protect video cassettes for their clients or themselves.
Starting in 1985 with the video release of "The Cotton Club", Macrovision has licensed to publishers a technology that exploits the automatic gain control feature of VCRs by adding pulses to the vertical blanking sync signal. These pulses do not affect the image a consumer sees on his TV, but do confuse the recording-level circuitry of consumer VCRs. This technology, which is aided by U.S. legislation mandating the presence of automatic gain-control circuitry in VCRs, is said to "plug the analog hole" and make VCR-to-VCR copies impossible, although an inexpensive circuit is widely available that will defeat the protection by removing the pulses. Macrovision has patented methods of defeating copy prevention, giving it a more straightforward basis to shut down manufacture of any device that descrambles it than often exists in the DRM world.
By 2000, Napster had become a popular mainstream hobby, and several music publishers responded by starting to sell some CDs with various copy protection schemes. Most of these are playback restrictions that aim to make the CD unusable in computers with CD-ROM drives, leaving only dedicated audio CD players for playback. This does not, however, prevent such a CD from being copied via analogue connections or by ripping the CD under operating systems such as Linux (which is effective since copy-protection software is generally written for Microsoft Windows), which has led critics to question the usefulness of such schemes.
CD copy protection is achieved by assuming certain feature levels in the drives: The CD Digital Audio is the oldest CD standard and forms the basic feature set beyond which dedicated audio players need no knowledge. CD-ROM drives additionally need to support mixed mode CDs (combined audio and data tracks) and multi-session CDs (multiple data recordings each superseding and incorporating data of the previous session).
The play preventions in use intentionally deviate from the standards and intentionally include malformed multisession data or similar with the purpose of confusing the CD-ROM drives to prevent correct function. Simple dedicated audio CD players would not be affected by the malformed data since these are for features they do not support — for example, an audio player will not even look for a second session containing the copy protection data.
In practice, results vary wildly. CD-ROM drives may be able to correct the malformed data and still play them to an extent that depends on the make and version of the drive. On the other hand, some audio players may be built around drives with more than the basic intelligence required for audio playback. Some car radios with CD playback, portable CD players, CD players with additional support for data CDs containing MP3 files, and DVD players have had problems with these CDs.
The deviation from the Red Book standard that defines audio CDs required the publishers of these copy-protected CDs to refrain from using the official CDDA logo on the discs or the cases. The logo is a trademark owned by Philips and Sony and licensed to identify compliant audio discs only. To prevent dissatisfied customers from returning CDs which were misrepresented as compliant audio CDs, such CDs also started to carry prominent notices on their covers.
More recently, publishers of music and movies in digital form have turned to encryption to make copying more difficult. CSS, which is used on DVDs, is a famous example of this. It is a form of copy protection that uses 40-bit encryption. Copies will not be playable since they will be missing the key, which is not writable on DVD-R or DVD-RW discs. With this technique, the work is encrypted using a key only included in the firmware of "authorized" players, which allow only "legitimate" uses of the work (usually restricted forms of playback, but no conversion or modification). The controversial Digital Millennium Copyright Act provides a legal protection for this in the US, that would make it illegal to distribute "unauthorized" players—which was supposed to eliminate the possibility of building a DVD copier. However, encryption schemes designed for mass-market standardized media such as DVD suffer from the fundamental weakness that once implemented, they can never be changed without breaking the standard. Since consumers are highly unlikely to buy new hardware for the sole purpose of preserving copy protection, manufacturers have been prevented from enhancing their DRM technology until recently, with the release of next-generation media such as HD DVD and Blu-ray Disc. This period represents more than enough time for the encryption scheme to be defeated by determined attackers. For example, the CSS encryption system used on DVD Video was broken within three years of its market release in November 1996 (see DeCSS), but has not been changed since, because doing so would immediately render all DVD players sold prior to the change incapable of reading new DVDs—this would not only provoke a furious backlash amongst consumers, but massively restrict the market that the new DVDs could be sold to. More recent DVDs have attempted to augment CSS with additional protection schemes. Most modern schemes like ARccOS Protection use tricks of the DVD format in an attempt to trip up pirating programs, though it is noted that any scheme must stay within the bounds of the DVD Video format, limiting the possible avenues of protection—and making it easier for hackers to learn the innards of the scheme and find ways around it.
The newest generations of optical disc media, HD DVD and Blu-ray Disc, attempt to address this issue. Both formats employ the Advanced Access Content System, which provides for several hundred different decryption keys (for the varying models of players to hit the market), each of which can be invalidated ("revoked") should one of the keys be compromised. Revoked keys simply will not appear on future discs, rendering the compromised players useless for future titles unless they are updated to fix the issue. For this reason, all HD-DVD players and some Blu-ray players include an ethernet port, to give them the ability to download DRM updates. Blu-ray Disc goes one step further with a separate technique called BD+, a virtual machine that can execute code included on discs to verify, authorize, revoke, and update players as the need arises. Since the protection program is on the disc rather than the player, this allows for updating protection programs within BD's working life by simply having newer programs included on newer discs.
Its a necessary evil to protect your IP; if not revenue.