Naming convention for .idlk files?

InDesign and InCopy avoid stepping on each other's toes by putting .idlk lock files in the same directory as files they're working on.

It's evident that the filename pattern is:

"~{lowercased filename}~{6-character string}.idlk"

Any documentation or ideas about how that 6-character string is generated? It seems to be based only on the filename-a checksum of some sort?

Thanks,

-Matt