How does CD-ROM copy protection work?
(2000/03/12) There are several possibilities; as yet no developers have come forward and announced what they’re doing (for obvious reasons). For anyone interested in protecting their own discs: don’t bother. Copy protection, on the whole, does not work. If you have a major application, such as a game or CAD package, you may want to consider one of the commercially licensed schemes listed later, or (heaven forbid) the use of a dongle. A simple and commonly seen technique is to increase the length of several files on the CD so that they appear to be hundreds of megabytes long. This is accomplished by setting the file length in the disc image to be much larger than it really is. The file actually overlaps with many other files. So long as the application knows the true file length, the software will work fine. If the user tries to copy the files onto their hard drive, or do a file-by-file disc copy, the attempt will fail because the CD will appear to hold a few GB of data. (In practice th
There are several possibilities; as yet no developers have come forward and announced what they’re doing (for obvious reasons). For anyone interested in protecting their own discs: don’t bother. Copy protection, on the whole, does not work. If you have a major application, such as a game or CAD package, you may want to consider one of the commercially licensed schemes listed later, or (heaven forbid) the use of a dongle. A simple and commonly seen technique is to increase the length of several files on the CD so that they appear to be hundreds of megabytes long. This is accomplished by setting the file length in the disc image to be much larger than it really is. The file actually overlaps with many other files. So long as the application knows the true file length, the software will work fine. If the user tries to copy the files onto their hard drive, or do a file-by-file disc copy, the attempt will fail because the CD will appear to hold a few GB of data. (In practice this doesn’t fo
There are several possibilities; as yet no developers have come forward and announced what they’re doing (for obvious reasons). A simple and commonly seen technique is to increase the length of several files on the CD so that they appear to be hundreds of megabytes long. This is accomplished by setting the file length in the disc image to be much larger than it really is. The file actually overlaps with many other files. So long as the application knows the true file length, the software will work fine. If the user tries to copy the files onto their hard drive, or do a file-by-file disc copy, the attempt will fail because the CD will appear to hold a few GB of data. (In practice this doesn’t foil pirates, because they always do image copies.) One possible implementation, given sufficient control over the reader and mastering software, is to write faulty data into the ECC portion of a data sector. Standard CD-ROM hardware will automatically correct the “errors”, writing a different set
