Ah, finally. I've stumbled over a reference implmentation of MD5 that seems it should work fine with Java 1.1.x. It's sitting on freeVBcode.com, a strange place for Java jive, and lives in a zip with VB and a dll in C. Still, seems to work just fine.

MD5 Message Digest Algorithm for Implementing Digitial Signatures:
MD5 Message Digest Algorithm for Implementing Digitial Signatures
Version Compatibility:
Visual Basic 6
[but also Java]


More information: Various ports of the MD5 RSA Reference Implementation. This includes a VB Native Class, a C DLL (with VB wrapper), and a
java port.


Really doesn't seem all that complicated a task, now that I've finally bothered to look up the RFC and this code. Regardless, done and done.