The primary technique used for this is mangling the header field storing the body size to generate an invalid value. Westwood's games seem to ignore the header information (thus allowing them to use the MIX despite the wrong header), while XCC compares the stated body size to the actual body size, and rejects the MIX if the stated body size is bigger than the actual body size.
Originally released by Saberhawk in 2005, LeechKiller is the oldest MIX protector available in the community. According to the information made public by aristurtle, LeechKiller uses a randomized header mangling technique described in his post; in addition to that, DCoder described in 2007 that LeechKiller also erases the internal reference to XCC's file index (lmd.dat) inside the mix, making it even harder to recover the contents.
It is of note that, even back then, it had already been admitted that a little bit of math would restore the MIX.
It is planned that DCoder's MIX DLL will include protection capabilities, however, this DLL has yet to be released. DCoder has stated that his tool will use the same method of protection as LeechKiller.
- Once released, the DLL will be used by LaunchBase, thus giving modders the ability to effortlessly create protected MIXs as part of the development process, without special preparation.
MIX Protector is a tool released in 2007 by VK. According to aristurtle, MIX Protector's protection is weaker than LeechKiller's, as it always increases the same position by the same value - this stands in contrast to statements by VK claiming "you can't restore it back" as well as hints towards more advanced techniques like "size cheking" [sic] and "CRC cheking" [sic].
- MIX files
- Announcement thread for LeechKiller on DeeZire
- Announcement thread for MIX Protector on RPNF
- Commentary by DCoder (on PPM)
- Commentary by DCoder (on RPNF)
- Unprotecting a protected MIX (original post on PPM)
- Unprotecting a protected MIX (formatted version on ModEnc)
- Recover Protected MIX Files using RA2YR MIX Unprotector Master
- Brief discussion on Revora about the practical use of MIX protection