diff --git a/kex.h b/kex.h
new file mode 100644
index 0000000..f9e7999
--- /dev/null
+++ b/kex.h
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2000 Markus Friedl.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *      This product includes software developed by Markus Friedl.
+ * 4. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef KEX_H
+#define KEX_H
+
+#define	KEX_DH1	"diffie-hellman-group1-sha1"
+#define KEX_DSS	"ssh-dss"
+
+enum kex_init_proposals {
+	PROPOSAL_KEX_ALGS,
+	PROPOSAL_SERVER_HOST_KEY_ALGS,
+	PROPOSAL_ENC_ALGS_CTOS,
+	PROPOSAL_ENC_ALGS_STOC,
+	PROPOSAL_MAC_ALGS_CTOS,
+	PROPOSAL_MAC_ALGS_STOC,
+	PROPOSAL_COMP_ALGS_CTOS,
+	PROPOSAL_COMP_ALGS_STOC,
+	PROPOSAL_LANG_CTOS,
+	PROPOSAL_LANG_STOC,
+	PROPOSAL_MAX
+};
+
+enum kex_modes {
+	MODE_IN,
+	MODE_OUT,
+	MODE_MAX
+};
+
+typedef struct Kex Kex;
+typedef struct Mac Mac;
+typedef struct Comp Comp;
+typedef struct Enc Enc;
+
+struct Enc {
+	int		type;
+	int		enabled;
+	int		block_size;
+	unsigned char	*key;
+	unsigned char	*iv;
+	int		key_len;
+	int		iv_len;
+	char		*name;
+};
+struct Mac {
+	EVP_MD		*md;
+	int		enabled;
+	int		mac_len;
+	unsigned char	*key;
+	int		key_len;
+	char		*name;
+};
+struct Comp {
+	int		type;
+	int		enabled;
+	char		*name;
+};
+struct Kex {
+	Enc		enc [MODE_MAX];
+	Mac		mac [MODE_MAX];
+	Comp		comp[MODE_MAX];
+	int		we_need;
+	int		server;
+	char		*name;
+	char		*hostkeyalg;
+};
+
+Buffer	*kex_init(char *myproposal[PROPOSAL_MAX]);
+DH	*new_dh_group1();
+Kex 	*kex_choose_conf(char *cprop[PROPOSAL_MAX], char *sprop[PROPOSAL_MAX], int server);
+int	kex_derive_keys(Kex *k, unsigned char *hash, BIGNUM *shared_secret);
+void	bignum_print(BIGNUM *b);
+void	packet_set_kex(Kex *k);
+
+unsigned char *
+kex_hash(
+    char *client_version_string,
+    char *server_version_string,
+    char *ckexinit, int ckexinitlen,
+    char *skexinit, int skexinitlen,
+    char *serverhostkeyblob, int sbloblen,
+    BIGNUM *client_dh_pub,
+    BIGNUM *server_dh_pub,
+    BIGNUM *shared_secret);
+
+#endif