This patch add `md5' support for emacs. It was developed for Emacs 21 but might apply to Emacs 20.x too. XEmacs already have md5 support.
Some test cases are available too.
2000-10-07 Simon Josefsson <simon@josefsson.org> * lisp.h: Export md5. * coding.h: Export Qwrite_region and Qcoding_system_error. * fns.c (Fmd5): New function. (syms_of_fns): defsubr md5. * Makefile.in (obj): Add md5.o * md5.{c,h}: New files, from glibc, by Ulrich Drepper <drepper@gnu.ai.mit.edu>.
The patch is available from here.