Yannick Gingras wrote: > I am wondering if there are any techniques to make a CD-Key of the like > unbreakable. Either by giving it a cancelation date and a periodic renewal > from a server or just by using self md5 signature on the resulting > executable. I know it must not be easy because the whole software piracy > problem would be resolved but there must be some way to make it really hard > to break it. Anyone have hints on this issue ? What do you mean by "CD-Key or the like" (I presume that "of" was a typo)? And what do you mean by "unbreakable"? You need to be far more explicit about the problem which you wish to solve, and about the constraints involved. Some general points: 1. For a conventional "CD key" system, where the actual CDs are mass-produced (where you have many identical CDs), and the entire system has to work offline, you cannot solve the problem of valid keys being "traded" (e.g. included along with bootleg copies of the product). If there's an online element involved, you can "tie" keys to a specific hardware configuration, as is done (AFAIK) for Windows XP's "product activation". 2. Anything which uses a symmetric cipher (or hash) is bound to be vulnerable to reverse engineering of the validation routines within the executable. 3. Ultimately, any software mechanism will be vulnerable to "cracking", i.e. modifying the software to disable or circumvent the validation checks. This can only be prevented by the use of trusted hardware (e.g. a Palladium-style system). Most significantly, the data must be supplied in a form which is only accessible by that hardware. If anyone can get at the data in a meaningful (i.e. unencrypted) form, they can extract the useful parts and discard the rest (i.e. any associated protection mechanisms). IOW, you have to "keep the genie in the bottle" at all times. If the data can be got at just once (even if it requires the use of dedicated hardware such as a bus analyser), it can then be duplicated and distributed without limit. -- Glynn Clements <glynn.clementsat_private>
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