diff --git a/krl.c b/krl.c
index a7f6909..89cb433 100644
--- a/krl.c
+++ b/krl.c
@@ -14,7 +14,7 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $OpenBSD: krl.c,v 1.44 2019/09/06 04:53:27 djm Exp $ */
+/* $OpenBSD: krl.c,v 1.45 2019/10/31 21:23:19 djm Exp $ */
 
 #include "includes.h"
 
@@ -813,7 +813,7 @@
 			goto out;
 
 		if ((r = sshkey_sign(sign_keys[i], &sblob, &slen,
-		    sshbuf_ptr(buf), sshbuf_len(buf), NULL, 0)) != 0)
+		    sshbuf_ptr(buf), sshbuf_len(buf), NULL, NULL, 0)) != 0)
 			goto out;
 		KRL_DBG(("%s: signature sig len %zu", __func__, slen));
 		if ((r = sshbuf_put_string(buf, sblob, slen)) != 0)
diff --git a/monitor.c b/monitor.c
index 00af44f..a884d5f 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor.c,v 1.199 2019/10/07 23:10:38 djm Exp $ */
+/* $OpenBSD: monitor.c,v 1.200 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -678,7 +678,7 @@
 
 	if ((key = get_hostkey_by_index(keyid)) != NULL) {
 		if ((r = sshkey_sign(key, &signature, &siglen, p, datlen, alg,
-		    compat)) != 0)
+		    NULL, compat)) != 0)
 			fatal("%s: sshkey_sign failed: %s",
 			    __func__, ssh_err(r));
 	} else if ((key = get_hostkey_public_by_index(keyid, ssh)) != NULL &&
diff --git a/monitor_wrap.c b/monitor_wrap.c
index 4169b76..d20dc51 100644
--- a/monitor_wrap.c
+++ b/monitor_wrap.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.c,v 1.113 2019/06/28 13:35:04 deraadt Exp $ */
+/* $OpenBSD: monitor_wrap.c,v 1.114 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
  * Copyright 2002 Markus Friedl <markus@openbsd.org>
@@ -215,7 +215,8 @@
 
 int
 mm_sshkey_sign(struct ssh *ssh, struct sshkey *key, u_char **sigp, size_t *lenp,
-    const u_char *data, size_t datalen, const char *hostkey_alg, u_int compat)
+    const u_char *data, size_t datalen, const char *hostkey_alg,
+    const char *sk_provider, u_int compat)
 {
 	struct kex *kex = *pmonitor->m_pkex;
 	struct sshbuf *m;
@@ -223,7 +224,8 @@
 	int r;
 
 	debug3("%s entering", __func__);
-
+	if (sk_provider != NULL)
+		fatal("%s: sk_provider != NULL", __func__);
 	if ((m = sshbuf_new()) == NULL)
 		fatal("%s: sshbuf_new failed", __func__);
 	if ((r = sshbuf_put_u32(m, ndx)) != 0 ||
diff --git a/monitor_wrap.h b/monitor_wrap.h
index 191277f..76330fc 100644
--- a/monitor_wrap.h
+++ b/monitor_wrap.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: monitor_wrap.h,v 1.42 2019/09/06 05:23:55 djm Exp $ */
+/* $OpenBSD: monitor_wrap.h,v 1.43 2019/10/31 21:23:19 djm Exp $ */
 
 /*
  * Copyright 2002 Niels Provos <provos@citi.umich.edu>
@@ -45,7 +45,7 @@
 DH *mm_choose_dh(int, int, int);
 #endif
 int mm_sshkey_sign(struct ssh *, struct sshkey *, u_char **, size_t *,
-    const u_char *, size_t, const char *, u_int compat);
+    const u_char *, size_t, const char *, const char *, u_int compat);
 void mm_inform_authserv(char *, char *);
 struct passwd *mm_getpwnamallow(struct ssh *, const char *);
 char *mm_auth2_read_banner(void);
diff --git a/ssh-agent.c b/ssh-agent.c
index 6bf9536..07f19c5 100644
--- a/ssh-agent.c
+++ b/ssh-agent.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-agent.c,v 1.238 2019/10/31 21:22:01 djm Exp $ */
+/* $OpenBSD: ssh-agent.c,v 1.239 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -430,12 +430,13 @@
 		if ((r = provider_sign(id->sk_provider, id->key, &signature,
 		    &slen, data, dlen, agent_decode_alg(key, flags),
 		    compat)) != 0) {
-			error("%s: sshkey_sign: %s", __func__, ssh_err(r));
+			error("%s: sign: %s", __func__, ssh_err(r));
 			goto send;
 		}
 	} else {
 		if ((r = sshkey_sign(id->key, &signature, &slen,
-		    data, dlen, agent_decode_alg(key, flags), compat)) != 0) {
+		    data, dlen, agent_decode_alg(key, flags),
+		    NULL, compat)) != 0) {
 			error("%s: sshkey_sign: %s", __func__, ssh_err(r));
 			goto send;
 		}
diff --git a/ssh-keygen.c b/ssh-keygen.c
index ad7a2b4..14bf256 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.357 2019/10/31 21:17:09 djm Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.358 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -577,8 +577,10 @@
 		error("%s: remaining bytes in key blob %d", __func__, rlen);
 
 	/* try the key */
-	if (sshkey_sign(key, &sig, &slen, data, sizeof(data), NULL, 0) != 0 ||
-	    sshkey_verify(key, sig, slen, data, sizeof(data), NULL, 0) != 0) {
+	if (sshkey_sign(key, &sig, &slen, data, sizeof(data),
+	    NULL, NULL, 0) != 0 ||
+	    sshkey_verify(key, sig, slen, data, sizeof(data),
+	    NULL, 0) != 0) {
 		sshkey_free(key);
 		free(sig);
 		return NULL;
@@ -1709,7 +1711,7 @@
 static int
 agent_signer(struct sshkey *key, u_char **sigp, size_t *lenp,
     const u_char *data, size_t datalen,
-    const char *alg, u_int compat, void *ctx)
+    const char *alg, const char *sk_provider, u_int compat, void *ctx)
 {
 	int *agent_fdp = (int *)ctx;
 
@@ -1821,11 +1823,13 @@
 
 		if (agent_fd != -1 && (ca->flags & SSHKEY_FLAG_EXT) != 0) {
 			if ((r = sshkey_certify_custom(public, ca,
-			    key_type_name, agent_signer, &agent_fd)) != 0)
+			    key_type_name, sk_provider, agent_signer,
+			    &agent_fd)) != 0)
 				fatal("Couldn't certify key %s via agent: %s",
 				    tmp, ssh_err(r));
 		} else {
-			if ((sshkey_certify(public, ca, key_type_name)) != 0)
+			if ((sshkey_certify(public, ca, key_type_name,
+			    sk_provider)) != 0)
 				fatal("Couldn't certify key %s: %s",
 				    tmp, ssh_err(r));
 		}
@@ -2507,7 +2511,7 @@
 		else
 			fprintf(stderr, "Signing file %s\n", filename);
 	}
-	if ((r = sshsig_sign_fd(signkey, NULL, fd, sig_namespace,
+	if ((r = sshsig_sign_fd(signkey, NULL, sk_provider, fd, sig_namespace,
 	    &sigbuf, signer, signer_ctx)) != 0) {
 		error("Signing %s failed: %s", filename, ssh_err(r));
 		goto out;
diff --git a/ssh-keysign.c b/ssh-keysign.c
index 6cfd5b4..d6aa636 100644
--- a/ssh-keysign.c
+++ b/ssh-keysign.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keysign.c,v 1.61 2019/10/02 00:42:30 djm Exp $ */
+/* $OpenBSD: ssh-keysign.c,v 1.62 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Copyright (c) 2002 Markus Friedl.  All rights reserved.
  *
@@ -277,8 +277,8 @@
 		    sshkey_type(key), fp ? fp : "");
 	}
 
-	if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen, NULL, 0))
-	    != 0)
+	if ((r = sshkey_sign(keys[i], &signature, &slen, data, dlen,
+	    NULL, NULL, 0)) != 0)
 		fatal("sshkey_sign failed: %s", ssh_err(r));
 	free(data);
 
diff --git a/ssh_api.c b/ssh_api.c
index 03dac09..e0b1955 100644
--- a/ssh_api.c
+++ b/ssh_api.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh_api.c,v 1.18 2019/09/13 04:36:43 dtucker Exp $ */
+/* $OpenBSD: ssh_api.c,v 1.19 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Copyright (c) 2012 Markus Friedl.  All rights reserved.
  *
@@ -54,7 +54,7 @@
  */
 int	use_privsep = 0;
 int	mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
-    u_char *, u_int, char *, u_int);
+    const u_char *, u_int, const char *, const char *, u_int);
 
 #ifdef WITH_OPENSSL
 DH	*mm_choose_dh(int, int, int);
@@ -66,7 +66,8 @@
 
 int
 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
-    u_char *data, u_int datalen, char *alg, u_int compat)
+    const u_char *data, u_int datalen, const char *alg, const char *sk_provider,
+    u_int compat)
 {
 	return (-1);
 }
@@ -568,5 +569,5 @@
     const u_char *data, size_t dlen, const char *alg)
 {
 	return sshkey_sign(privkey, signature, slen, data, dlen,
-	    alg, ssh->compat);
+	    alg, NULL, ssh->compat);
 }
diff --git a/sshconnect2.c b/sshconnect2.c
index 62f0c3e..867d463 100644
--- a/sshconnect2.c
+++ b/sshconnect2.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect2.c,v 1.309 2019/10/31 21:18:28 djm Exp $ */
+/* $OpenBSD: sshconnect2.c,v 1.310 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Damien Miller.  All rights reserved.
@@ -1178,19 +1178,8 @@
 		}
 		sign_key = prv;
 	}
-
-	if (sshkey_type_plain(sign_key->type) == KEY_ECDSA_SK) {
-		if (options.sk_provider == NULL) {
-			/* Shouldn't happen here; checked in pubkey_prepare() */
-			fatal("%s: missing SecurityKeyProvider", __func__);
-		}
-		if ((r = sshsk_ecdsa_sign(options.sk_provider, sign_key,
-		    sigp, lenp, data, datalen, compat)) != 0) {
-			debug("%s: sshsk_ecdsa_sign: %s", __func__, ssh_err(r));
-			goto out;
-		}
-	} else if ((r = sshkey_sign(sign_key, sigp, lenp, data, datalen,
-	    alg, compat)) != 0) {
+	if ((r = sshkey_sign(sign_key, sigp, lenp, data, datalen,
+	    alg, options.sk_provider, compat)) != 0) {
 		debug("%s: sshkey_sign: %s", __func__, ssh_err(r));
 		goto out;
 	}
diff --git a/sshd.c b/sshd.c
index cf7af1c..e782a99 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.538 2019/10/29 07:47:27 dtucker Exp $ */
+/* $OpenBSD: sshd.c,v 1.539 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2209,17 +2209,17 @@
 	if (use_privsep) {
 		if (privkey) {
 			if (mm_sshkey_sign(ssh, privkey, signature, slenp,
-			    data, dlen, alg, ssh->compat) < 0)
+			    data, dlen, alg, NULL, ssh->compat) < 0)
 				fatal("%s: privkey sign failed", __func__);
 		} else {
 			if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
-			    data, dlen, alg, ssh->compat) < 0)
+			    data, dlen, alg, NULL, ssh->compat) < 0)
 				fatal("%s: pubkey sign failed", __func__);
 		}
 	} else {
 		if (privkey) {
 			if (sshkey_sign(privkey, signature, slenp, data, dlen,
-			    alg, ssh->compat) < 0)
+			    alg, NULL, ssh->compat) < 0)
 				fatal("%s: privkey sign failed", __func__);
 		} else {
 			if ((r = ssh_agent_sign(auth_sock, pubkey,
diff --git a/sshkey.c b/sshkey.c
index d87fee8..4744dfb 100644
--- a/sshkey.c
+++ b/sshkey.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.c,v 1.85 2019/10/31 21:15:14 djm Exp $ */
+/* $OpenBSD: sshkey.c,v 1.86 2019/10/31 21:23:19 djm Exp $ */
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  * Copyright (c) 2008 Alexander von Gernler.  All rights reserved.
@@ -57,6 +57,7 @@
 #define SSHKEY_INTERNAL
 #include "sshkey.h"
 #include "match.h"
+#include "ssh-sk.h"
 
 #ifdef WITH_XMSS
 #include "sshkey-xmss.h"
@@ -2658,7 +2659,8 @@
 int
 sshkey_sign(struct sshkey *key,
     u_char **sigp, size_t *lenp,
-    const u_char *data, size_t datalen, const char *alg, u_int compat)
+    const u_char *data, size_t datalen,
+    const char *alg, const char *sk_provider, u_int compat)
 {
 	int was_shielded = sshkey_is_shielded(key);
 	int r2, r = SSH_ERR_INTERNAL_ERROR;
@@ -2682,6 +2684,11 @@
 	case KEY_ECDSA:
 		r = ssh_ecdsa_sign(key, sigp, lenp, data, datalen, compat);
 		break;
+	case KEY_ECDSA_SK_CERT:
+	case KEY_ECDSA_SK:
+		r = sshsk_ecdsa_sign(sk_provider, key, sigp, lenp,
+		    data, datalen, compat);
+		break;
 # endif /* OPENSSL_HAS_ECC */
 	case KEY_RSA_CERT:
 	case KEY_RSA:
@@ -2802,7 +2809,7 @@
 /* Sign a certified key, (re-)generating the signed certblob. */
 int
 sshkey_certify_custom(struct sshkey *k, struct sshkey *ca, const char *alg,
-    sshkey_certify_signer *signer, void *signer_ctx)
+    const char *sk_provider, sshkey_certify_signer *signer, void *signer_ctx)
 {
 	struct sshbuf *principals = NULL;
 	u_char *ca_blob = NULL, *sig_blob = NULL, nonce[32];
@@ -2934,7 +2941,7 @@
 
 	/* Sign the whole mess */
 	if ((ret = signer(ca, &sig_blob, &sig_len, sshbuf_ptr(cert),
-	    sshbuf_len(cert), alg, 0, signer_ctx)) != 0)
+	    sshbuf_len(cert), alg, sk_provider, 0, signer_ctx)) != 0)
 		goto out;
 	/* Check and update signature_type against what was actually used */
 	if ((ret = sshkey_get_sigtype(sig_blob, sig_len, &sigtype)) != 0)
@@ -2964,17 +2971,20 @@
 static int
 default_key_sign(struct sshkey *key, u_char **sigp, size_t *lenp,
     const u_char *data, size_t datalen,
-    const char *alg, u_int compat, void *ctx)
+    const char *alg, const char *sk_provider, u_int compat, void *ctx)
 {
 	if (ctx != NULL)
 		return SSH_ERR_INVALID_ARGUMENT;
-	return sshkey_sign(key, sigp, lenp, data, datalen, alg, compat);
+	return sshkey_sign(key, sigp, lenp, data, datalen, alg,
+	    sk_provider, compat);
 }
 
 int
-sshkey_certify(struct sshkey *k, struct sshkey *ca, const char *alg)
+sshkey_certify(struct sshkey *k, struct sshkey *ca, const char *alg,
+    const char *sk_provider)
 {
-	return sshkey_certify_custom(k, ca, alg, default_key_sign, NULL);
+	return sshkey_certify_custom(k, ca, alg, sk_provider,
+	    default_key_sign, NULL);
 }
 
 int
diff --git a/sshkey.h b/sshkey.h
index 2edcb13..1d36a24 100644
--- a/sshkey.h
+++ b/sshkey.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshkey.h,v 1.35 2019/10/31 21:15:14 djm Exp $ */
+/* $OpenBSD: sshkey.h,v 1.36 2019/10/31 21:23:19 djm Exp $ */
 
 /*
  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
@@ -189,12 +189,13 @@
     char *, size_t) __attribute__((__bounded__(__string__, 2, 3)));
 int	 sshkey_check_cert_sigtype(const struct sshkey *, const char *);
 
-int	 sshkey_certify(struct sshkey *, struct sshkey *, const char *);
+int	 sshkey_certify(struct sshkey *, struct sshkey *,
+    const char *, const char *);
 /* Variant allowing use of a custom signature function (e.g. for ssh-agent) */
 typedef int sshkey_certify_signer(struct sshkey *, u_char **, size_t *,
-    const u_char *, size_t, const char *, u_int, void *);
+    const u_char *, size_t, const char *, const char *, u_int, void *);
 int	 sshkey_certify_custom(struct sshkey *, struct sshkey *, const char *,
-    sshkey_certify_signer *, void *);
+    const char *, sshkey_certify_signer *, void *);
 
 int		 sshkey_ecdsa_nid_from_name(const char *);
 int		 sshkey_curve_name_to_nid(const char *);
@@ -223,7 +224,7 @@
 int	 sshkey_putb_plain(const struct sshkey *, struct sshbuf *);
 
 int	 sshkey_sign(struct sshkey *, u_char **, size_t *,
-    const u_char *, size_t, const char *, u_int);
+    const u_char *, size_t, const char *, const char *, u_int);
 int	 sshkey_verify(const struct sshkey *, const u_char *, size_t,
     const u_char *, size_t, const char *, u_int);
 int	 sshkey_check_sigtype(const u_char *, size_t, const char *);
diff --git a/sshsig.c b/sshsig.c
index b19cd07..8c7aba1 100644
--- a/sshsig.c
+++ b/sshsig.c
@@ -151,8 +151,9 @@
 
 static int
 sshsig_wrap_sign(struct sshkey *key, const char *hashalg,
-    const struct sshbuf *h_message, const char *sig_namespace,
-    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
+    const char *sk_provider, const struct sshbuf *h_message,
+    const char *sig_namespace, struct sshbuf **out,
+    sshsig_signer *signer, void *signer_ctx)
 {
 	int r;
 	size_t slen = 0;
@@ -184,14 +185,14 @@
 	if (signer != NULL) {
 		if ((r = signer(key, &sig, &slen,
 		    sshbuf_ptr(tosign), sshbuf_len(tosign),
-		    sign_alg, 0, signer_ctx)) != 0) {
+		    sign_alg, sk_provider, 0, signer_ctx)) != 0) {
 			error("Couldn't sign message: %s", ssh_err(r));
 			goto done;
 		}
 	} else {
 		if ((r = sshkey_sign(key, &sig, &slen,
 		    sshbuf_ptr(tosign), sshbuf_len(tosign),
-		    sign_alg, 0)) != 0) {
+		    sign_alg, sk_provider, 0)) != 0) {
 			error("Couldn't sign message: %s", ssh_err(r));
 			goto done;
 		}
@@ -425,7 +426,7 @@
 }
 
 int
-sshsig_signb(struct sshkey *key, const char *hashalg,
+sshsig_signb(struct sshkey *key, const char *hashalg, const char *sk_provider,
     const struct sshbuf *message, const char *sig_namespace,
     struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
 {
@@ -440,8 +441,8 @@
 		error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
 		goto out;
 	}
-	if ((r = sshsig_wrap_sign(key, hashalg, b, sig_namespace, out,
-	    signer, signer_ctx)) != 0)
+	if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, b,
+	    sig_namespace, out, signer, signer_ctx)) != 0)
 		goto out;
 	/* success */
 	r = 0;
@@ -551,7 +552,7 @@
 }
 
 int
-sshsig_sign_fd(struct sshkey *key, const char *hashalg,
+sshsig_sign_fd(struct sshkey *key, const char *hashalg, const char *sk_provider,
     int fd, const char *sig_namespace, struct sshbuf **out,
     sshsig_signer *signer, void *signer_ctx)
 {
@@ -566,8 +567,8 @@
 		error("%s: hash_file failed: %s", __func__, ssh_err(r));
 		return r;
 	}
-	if ((r = sshsig_wrap_sign(key, hashalg, b, sig_namespace, out,
-	    signer, signer_ctx)) != 0)
+	if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, b,
+	    sig_namespace, out, signer, signer_ctx)) != 0)
 		goto out;
 	/* success */
 	r = 0;
diff --git a/sshsig.h b/sshsig.h
index e3eeb60..487db11 100644
--- a/sshsig.h
+++ b/sshsig.h
@@ -22,7 +22,7 @@
 struct sshsigopt;
 
 typedef int sshsig_signer(struct sshkey *, u_char **, size_t *,
-    const u_char *, size_t, const char *, u_int, void *);
+    const u_char *, size_t, const char *, const char *, u_int, void *);
 
 /* Buffer-oriented API */
 
@@ -32,8 +32,9 @@
  * out is populated with the detached signature, or NULL on failure.
  */
 int sshsig_signb(struct sshkey *key, const char *hashalg,
-    const struct sshbuf *message, const char *sig_namespace,
-    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx);
+    const char *sk_provider, const struct sshbuf *message,
+    const char *sig_namespace, struct sshbuf **out,
+    sshsig_signer *signer, void *signer_ctx);
 
 /*
  * Verifies that a detached signature is valid and optionally returns key
@@ -52,8 +53,8 @@
  * out is populated with the detached signature, or NULL on failure.
  */
 int sshsig_sign_fd(struct sshkey *key, const char *hashalg,
-    int fd, const char *sig_namespace, struct sshbuf **out,
-    sshsig_signer *signer, void *signer_ctx);
+    const char *sk_provider, int fd, const char *sig_namespace,
+    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx);
 
 /*
  * Verifies that a detached signature over a file is valid and optionally