md5pickle was documented, but not declared. it didn't work either.
(didn't archive state->len, missed out the terminating null for enc64)

Reference: /n/sources/patch/applied/md5pickle
Date: Mon Apr  5 23:18:24 CES 2004

--- /sys/src/libsec/port/md5pickle.c	Mon Apr  5 23:18:24 2004
+++ /sys/src/libsec/port/md5pickle.c	Mon Apr  5 23:18:24 2004
@@ -7,11 +7,12 @@
 	char *p;
 	int m, n;
 
-	m = 4*9+4*((s->blen+3)/3);
+	m = 17+4*9+4*((s->blen+3)/3 + 1);
 	p = malloc(m);
 	if(p == nil)
 		return p;
-	n = sprint(p, "%8.8ux %8.8ux %8.8ux %8.8ux ",
+	n = sprint(p, "%16.16ullx %8.8ux %8.8ux %8.8ux %8.8ux ",
+		s->len,
 		s->state[0], s->state[1], s->state[2],
 		s->state[3]);
 	enc64(p+n, m-n, s->buf, s->blen);
@@ -26,6 +27,7 @@
 	s = malloc(sizeof(*s));
 	if(s == nil)
 		return nil;
+	s->len = strtoull(p, &p, 16);
 	s->state[0] = strtoul(p, &p, 16);
 	s->state[1] = strtoul(p, &p, 16);
 	s->state[2] = strtoul(p, &p, 16);
--- /sys/include/libsec.h	Mon Apr  5 23:18:24 2004
+++ /sys/include/libsec.h	Mon Apr  5 23:18:24 2004
@@ -150,6 +150,8 @@
 DigestState* sha1(uchar*, ulong, uchar*, DigestState*);
 DigestState* hmac_md5(uchar*, ulong, uchar*, ulong, uchar*, DigestState*);
 DigestState* hmac_sha1(uchar*, ulong, uchar*, ulong, uchar*, DigestState*);
+char* md5pickle(MD5state*);
+MD5state* md5unpickle(char*);
 char* sha1pickle(SHA1state*);
 SHA1state* sha1unpickle(char*);