diff --git a/Makefile b/Makefile
index 60666b3..04025f3 100644
--- a/Makefile
+++ b/Makefile
@@ -6,6 +6,14 @@ ARMTARGET?= -mcpu=cortex-m3 -mthumb -DSTROBE_SINGLE_THREAD=1
 #ARMCC?=clang-mp-9.0
 #ARMTARGET?= -nostdlib -ffreestanding -target arm-none-eabi -mcpu=cortex-m3 -mfloat-abi=soft  -mthumb
 
+PLATFORM != uname -s
+
+.if $(PLATFORM) == "Darwin"
+SOEXT=dylib
+.else
+.error Unsupported platform: $(PLATFORM)
+.endif
+
 PROG = lora.irr
 PROGEXT = .elf
 
@@ -86,12 +94,28 @@ CFLAGS+= -I$(STM32)/usb
 OBJS = $(SRCS:C/.c$/.o/)
 CFLAGS+= -Werror -Wall
 
+LIBLORA_TEST_SRCS= comms.c strobe.c x25519.c
+LIBLORA_TEST_OBJS= $(LIBLORA_TEST_SRCS:C/.c$/.no/)
+
+LIBLORA_TEST = liblora_test.$(SOEXT)
+$(LIBLORA_TEST): $(LIBLORA_TEST_OBJS)
+	$(CC) -shared -o $@ $(.ALLSRC)
+
+.MAIN: all
 .PHONY: all
 all: $(PROG)$(PROGEXT) $(PROG).list
 
 .PHONY: depend
-depend: $(SRCS)
-	$(ARMCC) $(ARMTARGET) $(CFLAGS) $(.ALLSRC) -MM > .depend || rm -f .depend
+depend: .arm_deps .test_deps
+
+.sinclude ".arm_deps"
+.sinclude ".test_deps"
+
+.arm_deps: $(SRCS)
+	$(ARMCC) $(ARMTARGET) $(CFLAGS) $(.ALLSRC) -MM > $@ || rm -f $@
+
+.test_deps: $(LIBLORA_TEST_SRCS)
+	$(CC) $(CFLAGS) $(.ALLSRC) -MM | sed -e 's/\.o:/\.no:/' > $@ || rm -f $@
 
 $(PROG)$(PROGEXT): $(OBJS)
 	$(ARMCC) $(ARMTARGET) -o $@ $(.ALLSRC) -T$(LINKER_SCRIPT) --specs=nosys.specs -Wl,--gc-sections -static --specs=nano.specs -Wl,--start-group -lc -lm -Wl,--end-group
@@ -104,8 +128,13 @@ runbuild: $(SRCS)
 	for i in $(.MAKEFILE_LIST) $(.ALLSRC) $$(gsed ':x; /\\$$/ { N; s/\\\n//; tx }' < .depend  | sed -e 's/^[^:]*://'); do if [ "$$i" != ".." ]; then echo $$i; fi; done | entr -d sh -c 'echo starting...; cd $(.CURDIR) && $(MAKE) $(.MAKEFLAGS) depend && $(MAKE) $(.MAKEFLAGS) all'
 
 .PHONY: runtests
-runtests: lora.py
-	ls $(.ALLSRC) | entr sh -c 'PYTHONPATH="$(.CURDIR)" python -m coverage run -m unittest lora && coverage report --omit=p/\* -m -i'
+runtests: Makefile lora_comms.py lora.py $(LIBLORA_TEST) $(LIBLORA_TEST_SRCS)
+	ls $(.ALLSRC) | entr sh -c '(cd $(.CURDIR) && $(MAKE) $(.MAKEFLAGS) $(LIBLORA_TEST)) && ((PYTHONPATH="$(.CURDIR)" python -m coverage run -m unittest lora && coverage report --omit=p/\* -m -i) 2>&1 | head -n 20)'
+
+# native objects
+.SUFFIXES: .no
+.c.no:
+	$(CC) $(CFLAGS) -c $< -o $@
 
 .c.o:
 	$(ARMCC) $(ARMTARGET) $(CFLAGS) -c $< -o $@
diff --git a/comms.c b/comms.c
new file mode 100644
index 0000000..2ae25a8
--- /dev/null
+++ b/comms.c
@@ -0,0 +1,110 @@
+#include <comms.h>
+#include <strobe_rng_init.h>
+
+static const size_t MAC_LEN = 8;
+static const size_t CHALLENGE_LEN = 16;
+static const uint8_t domain[] = "com.funkthat.lora.irrigation.shared.v0.0.1";
+
+size_t
+_strobe_state_size()
+{
+
+	return sizeof(strobe_s);
+}
+
+void
+comms_init(struct comms_state *cs, process_msgfunc_t pmf)
+{
+
+	*cs = (struct comms_state){
+		.cs_comm_state = COMMS_WAIT_REQUEST,
+		.cs_procmsg = pmf,
+	};
+
+	strobe_init(&cs->cs_start, domain, sizeof domain - 1);
+
+	/* copy starting state over to initial state */
+	cs->cs_state = cs->cs_start;
+
+}
+
+#define CONFIRMED_STR_BASE	"confirmed"
+#define CONFIRMED_STR		((const uint8_t *)CONFIRMED_STR_BASE)
+#define CONFIRMED_STR_LEN	(sizeof(CONFIRMED_STR_BASE) - 1)
+
+/*
+ * encrypted data to be processed is passed in via pbin.
+ *
+ * The pktbuf pointed to by pbout contains the buffer that a [encrypted]
+ * response will be written to.  The length needs to be updated, where 0
+ * means no reply.
+ */
+void
+comms_process(struct comms_state *cs, struct pktbuf pbin, struct pktbuf *pbout)
+{
+	uint8_t buf[64] = {};
+	struct pktbuf pbmsg, pbrep;
+	ssize_t cnt, ret, msglen;
+
+	strobe_attach_buffer(&cs->cs_state, pbin.pkt, pbin.pktlen);
+
+	cnt = strobe_get(&cs->cs_state, APP_CIPHERTEXT, buf, pbin.pktlen -
+	    MAC_LEN);
+	msglen = cnt;
+
+	cnt = strobe_get(&cs->cs_state, MAC, pbin.pkt +
+	    (pbin.pktlen - MAC_LEN), MAC_LEN);
+
+	/* XXX - cnt != MAC_LEN test case */
+
+	/*
+	 * if we have arrived here, MAC has been verified, and buf now
+	 * contains the data to operate upon.
+	 */
+
+	/* attach the buffer for output */
+	strobe_attach_buffer(&cs->cs_state, pbout->pkt, pbout->pktlen);
+
+	ret = 0;
+	switch (cs->cs_comm_state) {
+	case COMMS_WAIT_REQUEST:
+		/* XXX - reqreset check */
+
+		bare_strobe_randomize(buf, CHALLENGE_LEN);
+		ret = strobe_put(&cs->cs_state, APP_CIPHERTEXT, buf,
+		    CHALLENGE_LEN);
+		ret += strobe_put(&cs->cs_state, MAC, NULL, MAC_LEN);
+		cs->cs_comm_state = COMMS_WAIT_CONFIRM;
+		break;
+
+	case COMMS_WAIT_CONFIRM:
+		/* XXX - confirm check */
+		ret = strobe_put(&cs->cs_state, APP_CIPHERTEXT, CONFIRMED_STR,
+		    CONFIRMED_STR_LEN);
+		ret += strobe_put(&cs->cs_state, MAC, NULL, MAC_LEN);
+		cs->cs_comm_state = COMMS_PROCESS_MSGS;
+		break;
+
+	case COMMS_PROCESS_MSGS: {
+		uint8_t repbuf[pbout->pktlen - MAC_LEN];
+
+		memset(repbuf, '\x00', sizeof repbuf);
+
+		pbmsg.pkt = buf;
+		pbmsg.pktlen = msglen;
+
+		pbrep.pkt = repbuf;
+		pbrep.pktlen = sizeof repbuf;
+
+		cs->cs_procmsg(pbmsg, &pbrep);
+
+		ret = strobe_put(&cs->cs_state, APP_CIPHERTEXT, repbuf,
+		    pbrep.pktlen);
+		ret += strobe_put(&cs->cs_state, MAC, NULL, MAC_LEN);
+
+		break;
+	}
+	}
+
+	pbout->pktlen = ret;
+}
diff --git a/comms.h b/comms.h
new file mode 100644
index 0000000..e53062d
--- /dev/null
+++ b/comms.h
@@ -0,0 +1,31 @@
+#include <sys/types.h>
+#include <stdint.h>
+
+#include <strobe.h>
+
+struct pktbuf {
+	uint8_t	*pkt;
+	uint16_t pktlen;
+};
+
+/* first arg is input buffer, second arg is what will be sent as reply */
+typedef void (*process_msgfunc_t)(struct pktbuf, struct pktbuf *);
+
+enum comm_state {
+	COMMS_WAIT_REQUEST = 1,
+	COMMS_WAIT_CONFIRM,
+	COMMS_PROCESS_MSGS,
+};
+
+struct comms_state {
+	strobe_s		cs_state;
+	enum comm_state		cs_comm_state;
+	strobe_s		cs_start;	/* special starting state cache */
+
+	process_msgfunc_t	cs_procmsg;
+};
+
+size_t _strobe_state_size();
+
+void comms_init(struct comms_state *, process_msgfunc_t);
+void comms_process(struct comms_state *, struct pktbuf, struct pktbuf *);
diff --git a/lora.py b/lora.py
index 94c6ee9..f34bfa7 100644
--- a/lora.py
+++ b/lora.py
@@ -3,9 +3,12 @@ import functools
 import os
 import unittest
 
-from Strobe.Strobe import Strobe
+from Strobe.Strobe import Strobe, KeccakF
 from Strobe.Strobe import AuthenticationFailed
 
+import lora_comms
+from lora_comms import make_pktbuf
+
 domain = b'com.funkthat.lora.irrigation.shared.v0.0.1'
 
 # Response to command will be the CMD and any arguments if needed.
@@ -21,7 +24,7 @@ class LORANode(object):
 
 	def __init__(self, syncdatagram):
 		self.sd = syncdatagram
-		self.st = Strobe(domain)
+		self.st = Strobe(domain, F=KeccakF(800))
 
 	async def start(self):
 		msg = self.st.send_enc(os.urandom(16) + b'reqreset') + \
@@ -174,7 +177,7 @@ class TestLORANode(unittest.IsolatedAsyncioTestCase):
 	async def test_lora(self):
 		class TestSD(MockSyncDatagram):
 			async def runner(self):
-				l = Strobe(domain)
+				l = Strobe(domain, F=KeccakF(800))
 
 				# start handshake
 				r = await self.get()
@@ -243,4 +246,86 @@ class TestLORANode(unittest.IsolatedAsyncioTestCase):
 		self.assertTrue(tsd.sendq.empty())
 		self.assertTrue(tsd.recvq.empty())
 
-		print('done')
+	@timeout(2)
+	async def test_ccode(self):
+		_self = self
+		from ctypes import pointer, sizeof, c_uint8
+
+		# seed the RNG
+		prngseed = b'abc123'
+		lora_comms.strobe_seed_prng((c_uint8 *
+		    len(prngseed))(*prngseed), len(prngseed))
+
+		# Create the state for testing
+		commstate = lora_comms.CommsState()
+
+		# These are the expected messages and their arguments
+		exptmsgs = [
+			(CMD_WAITFOR, [ 30 ]),
+			(CMD_RUNFOR, [ 1, 50 ]),
+			(CMD_TERMINATE, [ ]),
+		]
+		def procmsg(msg, outbuf):
+			msgbuf = msg._from()
+			#print('procmsg:', repr(msg), repr(msgbuf), repr(outbuf))
+			cmd = msgbuf[0]
+			args = [ int.from_bytes(msgbuf[x:x + 4],
+			    byteorder='little') for x in range(1, len(msgbuf),
+			    4) ]
+
+			if exptmsgs[0] == (cmd, args):
+				exptmsgs.pop(0)
+				outbuf[0].pkt[0] = cmd
+				outbuf[0].pktlen = 1
+			else: #pragma: no cover
+				raise RuntimeError('cmd not found')
+
+		# wrap the callback function
+		cb = lora_comms.process_msgfunc_t(procmsg)
+
+		class CCodeSD(MockSyncDatagram):
+			async def runner(self):
+				for expectlen in [ 24, 17, 9, 9, 9 ]:
+					# get message
+					gb = await self.get()
+					r = make_pktbuf(gb)
+
+					outbytes = bytearray(64)
+					outbuf = make_pktbuf(outbytes)
+
+					# process the test message
+					lora_comms.comms_process(commstate, r,
+					    outbuf)
+
+					# make sure the reply matches length
+					_self.assertEqual(expectlen,
+					    outbuf.pktlen)
+
+					# pass the reply back
+					await self.put(outbytes[:outbuf.pktlen])
+
+		# Initialize everything
+		lora_comms.comms_init(commstate, cb)
+
+		# Create test fixture
+		tsd = CCodeSD()
+		l = LORANode(tsd)
+
+		# Send various messages
+		await l.start()
+
+		await l.waitfor(30)
+
+		await l.runfor(1, 50)
+
+		await l.terminate()
+
+		await tsd.drain()
+
+		# Make sure all messages have been processed
+		self.assertTrue(tsd.sendq.empty())
+		self.assertTrue(tsd.recvq.empty())
+
+		# Make sure all the expected messages have been
+		# processed.
+		self.assertFalse(exptmsgs)
diff --git a/lora_comms.py b/lora_comms.py
new file mode 100644
index 0000000..b2830b6
--- /dev/null
+++ b/lora_comms.py
@@ -0,0 +1,59 @@
+from ctypes import Structure, POINTER, CFUNCTYPE, pointer
+from ctypes import c_uint8, c_uint16, c_ssize_t, c_size_t, c_uint64
+from ctypes import CDLL
+
+class PktBuf(Structure):
+	_fields_ = [
+		('pkt', POINTER(c_uint8)),
+		('pktlen', c_uint16),
+	]
+
+	def _from(self):
+		return bytes(self.pkt[:self.pktlen])
+
+	def __repr__(self):
+		return 'PktBuf(pkt=%s, pktlen=%s)' % (repr(self._from()),
+		    self.pktlen)
+
+def make_pktbuf(s):
+	pb = PktBuf()
+
+	if isinstance(s, bytearray):
+		obj = s
+		pb.pkt = pointer(c_uint8.from_buffer(s))
+		#print('mp:', repr(pb.pkt))
+	else:
+		obj = (c_uint8 * len(s))(*s)
+		pb.pkt = obj
+
+	pb.pktlen = len(s)
+
+	pb._make_pktbuf_ref = (obj, s)
+
+	return pb
+
+process_msgfunc_t = CFUNCTYPE(None, PktBuf, POINTER(PktBuf))
+
+_lib = CDLL('liblora_test.dylib')
+
+_lib._strobe_state_size.restype = c_size_t
+_lib._strobe_state_size.argtypes = ()
+_strobe_state_u64_cnt = (_lib._strobe_state_size() + 7) // 8
+
+class CommsState(Structure):
+	_fields_ = [
+		# The alignment of these may be off
+		('cs_state', c_uint64 * _strobe_state_u64_cnt),
+		('cs_start', c_uint64 * _strobe_state_u64_cnt),
+		('cs_procmsg', process_msgfunc_t),
+	]
+
+for func, ret, args in [
+    ('comms_init', None, (POINTER(CommsState), process_msgfunc_t)),
+    ('comms_process', None, (POINTER(CommsState), PktBuf, POINTER(PktBuf))),
+    ('strobe_seed_prng', None, (POINTER(c_uint8), c_ssize_t)),
+    ]:
+	f = getattr(_lib, func)
+	f.restype = ret
+	f.argtypes = args
+	locals()[func] = f
diff --git a/strobe/strobe.c b/strobe/strobe.c
index fb521cc..d77749c 100644
--- a/strobe/strobe.c
+++ b/strobe/strobe.c
@@ -224,25 +224,6 @@ static ssize_t strobe_operate_0 (
         return -1;
     }
 
-    /* Read/write the control word */
-    strobe_serialized_control_t str = {
-        GET_CONTROL_TAG(flags),
-        receiving_the_length ? 0 : eswap_htole_sl(len)
-    };
-    if (!more) {
-        TRY(strobe_duplex(strobe, cwf, (uint8_t *)&str, sizeof(str.control) + length_bytes));
-    }
-    str.len = eswap_letoh_sl(str.len);
-
-    // Check received control word and length
-    if (  str.control != GET_CONTROL_TAG(flags)
-       || str.len > INT_MAX
-       || ((ssize_t)(len + str.len) > 0 && (ssize_t)str.len != len)
-    ) {
-        return -1;
-    }
-    len = str.len;
-
     if (flags & FLAG_NO_DATA) return 0;
 
     return strobe_duplex(strobe, flags, inside, len);