Let's be logical. Why would you need to "lock" (copy-protect) your DVD? You would need it if you distributed some content free of charge. It's pretty obvious that you have make money on that. And yet, you want some solution free of charge. Note that if such solution worked, it would prevent obtaining a copy of this content directly, even for the people who would give you the solution for free. Doesn't it tell you that it's not very likely to work.
It's more likely that doing such tricks for getting money would itself require money? Really good amount of money. No money for that? But market mechanism for such things are very different that asking a solution free of charge. One of such mechanism is called "loan", another one — "investment", both are related to financial risks.
Moreover, when you invest money, the effect can be very limited. Strictly speaking, this is plain impossible — please see Solution 1 — but you can create some hassles for some of the users, so they may give up trying to copy the content. No protection can guarantee result, it can filter out only some of the users, more likely those who would not make extra copies of the DVD. And those people will be deprived of protection of their investment. People really need reserved copies of all content, because DVD can easily be damages. As to the real pirates, your protection won't be too serious hassle. But first, think if your content is valuable enough to protect it or to break it. The idea of PIEBALDconsult to put a sticker can work better. :-)
Nevertheless, some protection does exist and widely used, but for DVD video:
http://en.wikipedia.org/wiki/List_of_Compact_Disc_and_DVD_copy_protection_schemes[
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—SA
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