diff --git a/lightningd/.gitignore b/lightningd/.gitignore
index c9af60b4c..4168578a6 100644
--- a/lightningd/.gitignore
+++ b/lightningd/.gitignore
@@ -1 +1,2 @@
 lightningd
+lightningd_hsm
diff --git a/lightningd/Makefile b/lightningd/Makefile
index acb017553..8783a409c 100644
--- a/lightningd/Makefile
+++ b/lightningd/Makefile
@@ -4,7 +4,7 @@
 lightningd-wrongdir:
 	$(MAKE) -C .. lightningd-all
 
-lightningd-all: lightningd/lightningd
+lightningd-all: lightningd/lightningd lightningd/lightningd_hsm
 
 default: lightningd-all
 
@@ -40,6 +40,8 @@ LIGHTNINGD_HEADERS := lightningd/lightningd.h	\
 
 $(LIGHTNINGD_OBJS) $(LIGHTNINGD_LIB_OBJS): $(LIGHTNINGD_HEADERS) $(LIGHTNINGD_JSMN_HEADERS) $(BITCOIN_HEADERS) $(CORE_HEADERS) $(GEN_HEADERS) $(CCAN_HEADERS) $(DAEMON_HEADERS) $(LIBBASE58_HEADERS)
 
+include lightningd/hsm/Makefile
+
 check-source: $(LIGHTNINGD_SRC:%=check-src-include-order/%)
 check-source: $(LIGHTNINGD_LIB_SRC:%=check-src-include-order/%)
 check-source: $(LIGHTNINGD_CLI_SRC:%=check-src-include-order/%)
diff --git a/lightningd/hsm/Makefile b/lightningd/hsm/Makefile
new file mode 100644
index 000000000..d76236a7c
--- /dev/null
+++ b/lightningd/hsm/Makefile
@@ -0,0 +1,66 @@
+#! /usr/bin/make
+
+# Designed to be run one level up
+lightningd/hsm-wrongdir:
+	$(MAKE) -C .. lightningd/hsm-all
+
+default: lightningd/hsm-all
+
+# Clients use this:
+LIGHTNINGD_HSM_CLIENT_HEADERS := lightningd/hsm/client.h
+LIGHTNINGD_HSM_CLIENT_SRC := lightningd/hsm/client.c lightningd/hsm/gen_hsm_client_wire.c
+LIGHTNINGD_HSM_CLIENT_OBJS := $(LIGHTNINGD_HSM_CLIENT_SRC:.c=.o)
+
+# Control daemon uses this:
+LIGHTNINGD_HSM_CONTROL_HEADERS := lightningd/hsm/gen_hsm_control_wire.h
+LIGHTNINGD_HSM_CONTROL_SRC := lightningd/hsm/gen_hsm_control_wire.c
+LIGHTNINGD_HSM_CONTROL_OBJS := $(LIGHTNINGD_HSM_CONTROL_SRC:.c=.o)
+
+# lightningd/hsm needs these:
+LIGHTNINGD_HSM_HEADERS := lightningd/hsm/gen_hsm_client_wire.h	\
+	lightningd/hsm/gen_hsm_control_wire.h			\
+	lightningd/hsm/gen_hsm_status_wire.h
+LIGHTNINGD_HSM_SRC := lightningd/hsm/hsm.c	\
+	$(LIGHTNINGD_HSM_HEADERS:.h=.c)
+LIGHTNINGD_HSM_OBJS := $(LIGHTNINGD_HSM_SRC:.c=.o)
+
+# For checking
+LIGHTNINGD_HSM_ALLSRC_NOGEN := $(filter-out lightningd/hsm/gen_%, $(LIGHTNINGD_HSM_CLIENT_SRC) $(LIGHTNINGD_HSM_SRC))
+LIGHTNINGD_HSM_ALLHEADERS_NOGEN := $(filter-out lightningd/hsm/gen_%, $(LIGHTNINGD_HSM_CLIENT_HEADERS) $(LIGHTNINGD_HSM_HEADERS))
+
+$(LIGHTNINGD_HSM_OBJS) $(LIGHTNINGD_HSM_CLIENT_OBJS): $(CCAN_HEADERS) $(CORE_HEADERS) $(BITCOIN_HEADERS) $(GEN_HEADERS) $(WIRE_HEADERS) $(LIGHTNINGD_HSM_HEADERS) $(LIGHTNINGD_HSM_GEN_HEADERS) $(LIBBASE58_HEADERS)
+
+lightningd/hsm-all: lightningd/lightningd_hsm $(LIGHTNINGD_HSM_CLIENT_OBJS)
+
+lightningd/lightningd_hsm: $(LIGHTNINGD_HSM_OBJS) $(CORE_OBJS) $(BITCOIN_OBJS) $(WIRE_OBJS) $(CCAN_OBJS) $(LIBBASE58_OBJS) libsecp256k1.a
+	$(CC) $(CFLAGS) -o $@ $^ $(LDLIBS)
+
+lightningd/hsm/gen_hsm_client_wire.h: $(WIRE_GEN) lightningd/hsm/hsm_client_wire_csv
+	$(WIRE_GEN) --header $@ hsm_client_wire_type < lightningd/hsm/hsm_client_wire_csv > $@
+
+lightningd/hsm/gen_hsm_client_wire.c: $(WIRE_GEN) lightningd/hsm/hsm_client_wire_csv
+	$(WIRE_GEN) ${@:.c=.h} hsm_client_wire_type< lightningd/hsm/hsm_client_wire_csv > $@
+
+lightningd/hsm/gen_hsm_control_wire.h: $(WIRE_GEN) lightningd/hsm/hsm_control_wire_csv
+	$(WIRE_GEN) --header $@ hsm_control_wire_type < lightningd/hsm/hsm_control_wire_csv > $@
+
+lightningd/hsm/gen_hsm_control_wire.c: $(WIRE_GEN) lightningd/hsm/hsm_control_wire_csv
+	$(WIRE_GEN) ${@:.c=.h} hsm_control_wire_type < lightningd/hsm/hsm_control_wire_csv > $@
+
+lightningd/hsm/gen_hsm_status_wire.h: $(WIRE_GEN) lightningd/hsm/hsm_status_wire_csv
+	$(WIRE_GEN) --header $@ hsm_status_wire_type < lightningd/hsm/hsm_status_wire_csv > $@
+
+lightningd/hsm/gen_hsm_status_wire.c: $(WIRE_GEN) lightningd/hsm/hsm_status_wire_csv
+	$(WIRE_GEN) ${@:.c=.h} hsm_status_wire_type < lightningd/hsm/hsm_status_wire_csv > $@
+
+check-source: $(LIGHTNINGD_HSM_ALLSRC_NOGEN:%=check-src-include-order/%) $(LIGHTNINGD_HSM_ALLHEADERS_NOGEN:%=check-hdr-include-order/%)
+check-source-bolt: $(LIGHTNINGD_HSM_SRC:%=bolt-check/%) $(LIGHTNINGD_HSM_HEADERS:%=bolt-check/%)
+
+check-whitespace: $(LIGHTNINGD_HSM_ALLSRC_NOGEN:%=check-whitespace/%) $(LIGHTNINGD_HSM_ALLHEADERS_NOGEN:%=check-whitespace/%)
+
+clean: lightningd/hsm-clean
+
+lightningd/hsm-clean:
+	$(RM) $(LIGHTNINGD_HSM_OBJS) gen_*
+
+-include lightningd/hsm/test/Makefile 
diff --git a/lightningd/hsm/client.c b/lightningd/hsm/client.c
new file mode 100644
index 000000000..a3d4c5588
--- /dev/null
+++ b/lightningd/hsm/client.c
@@ -0,0 +1,31 @@
+#include <lightningd/hsm/client.h>
+#include <lightningd/hsm/gen_hsm_client_wire.h>
+#include <wire/wire_sync.h>
+
+static int hsm_fd = -1;
+
+void hsm_setup(int fd)
+{
+	hsm_fd = fd;
+}
+
+bool hsm_do_ecdh(struct sha256 *ss, const struct pubkey *point)
+{
+	u8 *req = towire_hsm_ecdh_req(NULL, point), *resp;
+	size_t len;
+
+	if (!wire_sync_write(hsm_fd, req))
+		goto fail;
+	resp = wire_sync_read(req, hsm_fd);
+	if (!resp)
+		goto fail;
+	len = tal_count(resp);
+	if (!fromwire_hsm_ecdh_resp(resp, &len, ss))
+		goto fail;
+	tal_free(req);
+	return true;
+
+fail:
+	tal_free(req);
+	return false;
+}
diff --git a/lightningd/hsm/client.h b/lightningd/hsm/client.h
new file mode 100644
index 000000000..d1be785f1
--- /dev/null
+++ b/lightningd/hsm/client.h
@@ -0,0 +1,17 @@
+/* API to ask the HSM for things. */
+#ifndef LIGHTNING_LIGHTNINGD_HSM_H
+#define LIGHTNING_LIGHTNINGD_HSM_H
+#include "config.h"
+#include <ccan/endian/endian.h>
+#include <ccan/short_types/short_types.h>
+#include <stdbool.h>
+
+struct pubkey;
+struct sha256;
+
+/* Setup communication to the HSM */
+void hsm_setup(int fd);
+
+/* Do ECDH using this node id secret. */
+bool hsm_do_ecdh(struct sha256 *ss, const struct pubkey *point);
+#endif /* LIGHTNING_LIGHTNINGD_HSM_H */
diff --git a/lightningd/hsm/hsm.c b/lightningd/hsm/hsm.c
new file mode 100644
index 000000000..0c3e17dd8
--- /dev/null
+++ b/lightningd/hsm/hsm.c
@@ -0,0 +1,303 @@
+#include <bitcoin/privkey.h>
+#include <bitcoin/pubkey.h>
+#include <ccan/breakpoint/breakpoint.h>
+#include <ccan/container_of/container_of.h>
+#include <ccan/crypto/hkdf_sha256/hkdf_sha256.h>
+#include <ccan/endian/endian.h>
+#include <ccan/fdpass/fdpass.h>
+#include <ccan/io/fdpass/fdpass.h>
+#include <ccan/io/io.h>
+#include <ccan/noerr/noerr.h>
+#include <ccan/read_write_all/read_write_all.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <lightningd/hsm/client.h>
+#include <lightningd/hsm/gen_hsm_client_wire.h>
+#include <lightningd/hsm/gen_hsm_control_wire.h>
+#include <lightningd/hsm/gen_hsm_status_wire.h>
+#include <secp256k1_ecdh.h>
+#include <sodium/randombytes.h>
+#include <status.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <utils.h>
+#include <version.h>
+#include <wire/wire_io.h>
+
+/* Nobody will ever find it here! */
+static struct privkey hsm_secret;
+
+struct conn_info {
+	struct io_plan *(*received_req)(struct io_conn *, struct conn_info *);
+	u8 *in;
+	u8 *out;
+	int out_fd;
+};
+
+struct client {
+	struct conn_info ci;
+	u64 id;
+	u8 *(*handle)(struct client *c, const tal_t *data);
+};
+
+static void node_key(struct privkey *node_secret, struct pubkey *node_id)
+{
+	u32 salt = 0;
+	struct privkey unused_s;
+	struct pubkey unused_k;
+
+	if (node_secret == NULL)
+		node_secret = &unused_s;
+	else if (node_id == NULL)
+		node_id = &unused_k;
+
+	do {
+		hkdf_sha256(node_secret, sizeof(*node_secret),
+			    &salt, sizeof(salt),
+			    &hsm_secret, sizeof(hsm_secret),
+			    "nodeid", 6);
+		salt++;
+	} while (!secp256k1_ec_pubkey_create(secp256k1_ctx, &node_id->pubkey,
+					     node_secret->secret));
+}
+
+static void conn_info_init(struct conn_info *ci,
+			   struct io_plan *(*received_req)(struct io_conn *conn,
+							   struct conn_info *ci))
+{
+	ci->received_req = received_req;
+	ci->in = ci->out = NULL;
+	ci->out_fd = -1;
+}
+
+static struct io_plan *sent_resp(struct io_conn *conn, struct conn_info *ci);
+
+/* Client operations */
+static struct io_plan *client_received_req(struct io_conn *conn,
+					   struct conn_info *ci)
+{
+	struct client *c = container_of(ci, struct client, ci);
+
+	status_trace("Client %"PRIu64": type %s len %zu",
+		     c->id,
+		     hsm_client_wire_type_name(fromwire_peektype(ci->in)),
+		     tal_count(ci->in));
+
+	ci->out = c->handle(c, ci->in);
+	if (!ci->out) {
+		status_send(towire_hsmstatus_client_bad_request(c, c->id,
+								ci->in));
+		return io_close(conn);
+	}
+	ci->in = tal_free(ci->in);
+	return io_write_wire(conn, ci->out, sent_resp, ci);
+}
+
+static struct client *new_client(const tal_t *ctx,
+				 u64 id,
+				 u8 *(*handle)(struct client *c,
+					       const tal_t *data))
+{
+	struct client *c = tal(ctx, struct client);
+	c->id = id;
+	c->handle = handle;
+	conn_info_init(&c->ci, client_received_req);
+
+	return c;
+}
+
+static u8 *handle_ecdh(struct client *c, const void *data)
+{
+	struct privkey privkey;
+	struct pubkey point;
+	struct sha256 ss;
+
+	if (!fromwire_hsm_ecdh_req(data, NULL, &point))
+		return NULL;
+
+	node_key(&privkey, NULL);
+	if (secp256k1_ecdh(secp256k1_ctx, ss.u.u8, &point.pubkey,
+			   privkey.secret) != 1)
+		return NULL;
+
+	return towire_hsm_ecdh_resp(c, &ss);
+}
+
+/* Control messages */
+static u8 *init_response(struct conn_info *control)
+{
+	struct pubkey node_id;
+	node_key(NULL, &node_id);
+	return towire_hsmctl_init_response(control, &node_id);
+}
+
+static u8 *create_new_hsm(struct conn_info *control)
+{
+	int fd = open("hsm_secret", O_CREAT|O_EXCL|O_WRONLY, 0400);
+	if (fd < 0)
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "creating: %s", strerror(errno));
+
+	randombytes_buf(&hsm_secret, sizeof(hsm_secret));
+	if (!write_all(fd, &hsm_secret, sizeof(hsm_secret))) {
+		unlink_noerr("hsm_secret");
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "writing: %s", strerror(errno));
+	}
+	if (fsync(fd) != 0) {
+		unlink_noerr("hsm_secret");
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "fsync: %s", strerror(errno));
+	}
+	if (close(fd) != 0) {
+		unlink_noerr("hsm_secret");
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "closing: %s", strerror(errno));
+	}
+	fd = open(".", O_RDONLY);
+	if (fsync(fd) != 0) {
+		unlink_noerr("hsm_secret");
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "fsyncdir: %s", strerror(errno));
+	}
+	close(fd);
+
+	return init_response(control);
+}
+
+static u8 *load_hsm(struct conn_info *control)
+{
+	int fd = open("hsm_secret", O_RDONLY);
+	if (fd < 0)
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "opening: %s", strerror(errno));
+	if (!read_all(fd, &hsm_secret, sizeof(hsm_secret)))
+		status_failed(WIRE_HSMSTATUS_INIT_FAILED,
+			      "reading: %s", strerror(errno));
+	close(fd);
+
+	return init_response(control);
+}
+
+static struct io_plan *recv_req(struct io_conn *conn, struct conn_info *ci)
+{
+	return io_read_wire(conn, ci, &ci->in, ci->received_req, ci);
+}
+
+static struct io_plan *sent_out_fd(struct io_conn *conn, struct conn_info *ci)
+{
+	ci->out_fd = -1;
+	return recv_req(conn, ci);
+}
+
+static struct io_plan *sent_resp(struct io_conn *conn, struct conn_info *ci)
+{
+	ci->out = tal_free(ci->out);
+	if (ci->out_fd != -1)
+		return io_send_fd(conn, ci->out_fd, sent_out_fd, ci);
+	return recv_req(conn, ci);
+}
+
+static struct io_plan *ecdh_client(struct io_conn *conn, struct client *c)
+{
+	tal_steal(conn, c);
+	return recv_req(conn, &c->ci);
+}
+
+static u8 *pass_hsmfd_ecdh(struct io_conn *conn,
+			   struct conn_info *control,
+			   const tal_t *data,
+			   int *fd_to_pass)
+{
+	int fds[2];
+	u64 id;
+	struct client *c;
+
+	if (!fromwire_hsmctl_hsmfd_ecdh(data, NULL, &id))
+		status_failed(WIRE_HSMSTATUS_BAD_REQUEST, "bad HSMFD_ECDH");
+
+	if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds) != 0)
+		status_failed(WIRE_HSMSTATUS_FD_FAILED,
+			      "creating fds: %s", strerror(errno));
+
+	c = new_client(control, id, handle_ecdh);
+	io_new_conn(control, fds[0], ecdh_client, c);
+
+	*fd_to_pass = fds[1];
+	return towire_hsmctl_hsmfd_ecdh_response(control);
+}
+
+static struct io_plan *control_received_req(struct io_conn *conn,
+					    struct conn_info *control)
+{
+	enum hsm_control_wire_type t = fromwire_peektype(control->in);
+
+	status_trace("Control: type %s len %zu",
+		     hsm_control_wire_type_name(t), tal_count(control->in));
+
+	switch (t) {
+	case WIRE_HSMCTL_INIT_NEW:
+		control->out = create_new_hsm(control);
+		goto send_out;
+	case WIRE_HSMCTL_INIT_LOAD:
+		control->out = load_hsm(control);
+		goto send_out;
+	case WIRE_HSMCTL_HSMFD_ECDH:
+		control->out = pass_hsmfd_ecdh(conn, control, control->in,
+					       &control->out_fd);
+		goto send_out;
+	case WIRE_HSMCTL_SHUTDOWN:
+		io_break(control);
+		return io_never(conn, control);
+
+	case WIRE_HSMCTL_INIT_RESPONSE:
+	case WIRE_HSMCTL_HSMFD_ECDH_RESPONSE:
+		break;
+	}
+
+	/* Control shouldn't give bad requests. */
+	status_failed(WIRE_HSMSTATUS_BAD_REQUEST, "%i", t);
+
+send_out:
+	if (control->out)
+		return io_write_wire(conn, control->out, sent_resp, control);
+	else
+		return sent_resp(conn, control);
+}
+
+static struct io_plan *control_init(struct io_conn *conn,
+				    struct conn_info *control)
+{
+	return recv_req(conn, control);
+}
+
+#ifndef TESTING
+int main(int argc, char *argv[])
+{
+	struct conn_info *control;
+
+	if (argc == 2 && streq(argv[1], "--version")) {
+		printf("%s\n", version());
+		exit(0);
+	}
+
+	breakpoint();
+	secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
+						 | SECP256K1_CONTEXT_SIGN);
+
+	control = tal(NULL, struct conn_info);
+	conn_info_init(control, control_received_req);
+
+	/* Stdout == status, stdin == requests */
+	status_setup(STDOUT_FILENO);
+
+	io_new_conn(control, STDIN_FILENO, control_init, control);
+	io_loop(NULL, NULL);
+
+	tal_free(control);
+	return 0;
+}
+#endif
diff --git a/lightningd/hsm/hsm_client_wire_csv b/lightningd/hsm/hsm_client_wire_csv
new file mode 100644
index 000000000..693e2991d
--- /dev/null
+++ b/lightningd/hsm/hsm_client_wire_csv
@@ -0,0 +1,5 @@
+# Give me ECDH(node-id-secret,point)
+hsm_ecdh_req,1
+hsm_ecdh_req,0,point,33
+hsm_ecdh_resp,100
+hsm_ecdh_resp,0,ss,32
diff --git a/lightningd/hsm/hsm_control_wire_csv b/lightningd/hsm/hsm_control_wire_csv
new file mode 100644
index 000000000..7224af3cc
--- /dev/null
+++ b/lightningd/hsm/hsm_control_wire_csv
@@ -0,0 +1,16 @@
+# These both respond with init_response
+hsmctl_init_new,1
+hsmctl_init_load,2
+
+hsmctl_init_response,100
+hsmctl_init_response,0,node_id,33
+
+# ECDH returns an fd.
+hsmctl_hsmfd_ecdh,3
+hsmctl_hsmfd_ecdh,0,unique_id,8
+
+# No message, just an fd.
+hsmctl_hsmfd_ecdh_response,103
+
+# Shutdown just results in an exit.
+hsmctl_shutdown,4
diff --git a/lightningd/hsm/hsm_status_wire_csv b/lightningd/hsm/hsm_status_wire_csv
new file mode 100644
index 000000000..807b5bb75
--- /dev/null
+++ b/lightningd/hsm/hsm_status_wire_csv
@@ -0,0 +1,11 @@
+# These are fatal.
+hsmstatus_init_failed,0x8000
+hsmstatus_writemsg_failed,0x8001
+hsmstatus_bad_request,0x8002
+hsmstatus_fd_failed,0x8003
+
+# Clients should not give a bad request but not the HSM's decision to crash.
+hsmstatus_client_bad_request,1
+hsmstatus_client_bad_request,0,unique-id,8
+hsmstatus_client_bad_request,8,len,2
+hsmstatus_client_bad_request,10,msg,len,u8
diff --git a/lightningd/lightningd.c b/lightningd/lightningd.c
index 3cf7844ae..e8c7015a7 100644
--- a/lightningd/lightningd.c
+++ b/lightningd/lightningd.c
@@ -94,7 +94,8 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 }
 
 static const char *daemons[] = {
-	"lightningd"
+	"lightningd",
+	"lightningd_hsm"
 };
 
 /* Check we can run them, and check their versions */