diff --git a/ssh.c b/ssh.c
index ab6d6fbe..f4061894 100644
--- a/ssh.c
+++ b/ssh.c
@@ -691,7 +691,7 @@ struct ssh_tag {
     int v2_session_id_len;
     int v2_cbc_ignore_workaround;
     int v2_out_cipherblksize;
-    void *kex_ctx;
+    struct dh_ctx *dh_ctx;
 
     int bare_connection;
     int attempting_connshare;
@@ -5787,12 +5787,12 @@ static void do_ssh2_transport(void *vctx)
                 bombout(("unable to read mp-ints from incoming group packet"));
                 crStopV;
             }
-            ssh->kex_ctx = dh_setup_gex(s->p, s->g);
+            ssh->dh_ctx = dh_setup_gex(s->p, s->g);
             s->kex_init_value = SSH2_MSG_KEX_DH_GEX_INIT;
             s->kex_reply_value = SSH2_MSG_KEX_DH_GEX_REPLY;
         } else {
             ssh->pls.kctx = SSH2_PKTCTX_DHGROUP;
-            ssh->kex_ctx = dh_setup_group(ssh->kex);
+            ssh->dh_ctx = dh_setup_group(ssh->kex);
             s->kex_init_value = SSH2_MSG_KEXDH_INIT;
             s->kex_reply_value = SSH2_MSG_KEXDH_REPLY;
             logeventf(ssh, "Using Diffie-Hellman with standard group \"%s\"",
@@ -5805,7 +5805,7 @@ static void do_ssh2_transport(void *vctx)
          * Now generate and send e for Diffie-Hellman.
          */
         set_busy_status(ssh->frontend, BUSY_CPU); /* this can take a while */
-        s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2);
+        s->e = dh_create_e(ssh->dh_ctx, s->nbits * 2);
         s->pktout = ssh_bpp_new_pktout(ssh->bpp, s->kex_init_value);
         put_mp_ssh2(s->pktout, s->e);
         ssh_pkt_write(ssh, s->pktout);
@@ -5827,13 +5827,13 @@ static void do_ssh2_transport(void *vctx)
         }
 
         {
-            const char *err = dh_validate_f(ssh->kex_ctx, s->f);
+            const char *err = dh_validate_f(ssh->dh_ctx, s->f);
             if (err) {
                 bombout(("key exchange reply failed validation: %s", err));
                 crStopV;
             }
         }
-        s->K = dh_find_K(ssh->kex_ctx, s->f);
+        s->K = dh_find_K(ssh->dh_ctx, s->f);
 
         /* We assume everything from now on will be quick, and it might
          * involve user interaction. */
@@ -5852,7 +5852,7 @@ static void do_ssh2_transport(void *vctx)
         put_mp_ssh2(ssh->exhash, s->e);
         put_mp_ssh2(ssh->exhash, s->f);
 
-        dh_cleanup(ssh->kex_ctx);
+        dh_cleanup(ssh->dh_ctx);
         freebn(s->f);
         if (dh_is_gex(ssh->kex)) {
             freebn(s->g);
@@ -5972,9 +5972,9 @@ static void do_ssh2_transport(void *vctx)
                 bombout(("unable to read mp-ints from incoming group packet"));
                 crStopV;
             }
-            ssh->kex_ctx = dh_setup_gex(s->p, s->g);
+            ssh->dh_ctx = dh_setup_gex(s->p, s->g);
         } else {
-            ssh->kex_ctx = dh_setup_group(ssh->kex);
+            ssh->dh_ctx = dh_setup_group(ssh->kex);
             logeventf(ssh, "Using GSSAPI (with Kerberos V5) Diffie-Hellman with standard group \"%s\"",
                       ssh->kex->groupname);
         }
@@ -5983,7 +5983,7 @@ static void do_ssh2_transport(void *vctx)
                   ssh->kex->hash->text_name);
         /* Now generate e for Diffie-Hellman. */
         set_busy_status(ssh->frontend, BUSY_CPU); /* this can take a while */
-        s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2);
+        s->e = dh_create_e(ssh->dh_ctx, s->nbits * 2);
 
         if (ssh->gsslib->gsslogmsg)
             logevent(ssh->gsslib->gsslogmsg);
@@ -6137,7 +6137,7 @@ static void do_ssh2_transport(void *vctx)
                  s->gss_stat == SSH_GSS_S_CONTINUE_NEEDED ||
                  !s->complete_rcvd);
 
-        s->K = dh_find_K(ssh->kex_ctx, s->f);
+        s->K = dh_find_K(ssh->dh_ctx, s->f);
 
         /* We assume everything from now on will be quick, and it might
          * involve user interaction. */
@@ -6162,7 +6162,7 @@ static void do_ssh2_transport(void *vctx)
          * used as the MIC input.
          */
 
-        dh_cleanup(ssh->kex_ctx);
+        dh_cleanup(ssh->dh_ctx);
         freebn(s->f);
         if (dh_is_gex(ssh->kex)) {
             freebn(s->g);
@@ -6313,7 +6313,7 @@ static void do_ssh2_transport(void *vctx)
     }
 #endif
 
-    ssh->kex_ctx = NULL;
+    ssh->dh_ctx = NULL;
 
 #if 0
     debug(("Exchange hash is:\n"));
@@ -10554,7 +10554,7 @@ static const char *ssh_init(Frontend *frontend, Backend **backend_handle,
     ssh->version = 0;		       /* when not ready yet */
     ssh->s = NULL;
     ssh->kex = NULL;
-    ssh->kex_ctx = NULL;
+    ssh->dh_ctx = NULL;
     ssh->hostkey_alg = NULL;
     ssh->hostkey_str = NULL;
     ssh->exitcode = -1;
@@ -10711,8 +10711,8 @@ static void ssh_free(Backend *be)
     struct X11FakeAuth *auth;
     int need_random_unref;
 
-    if (ssh->kex_ctx)
-	dh_cleanup(ssh->kex_ctx);
+    if (ssh->dh_ctx)
+        dh_cleanup(ssh->dh_ctx);
     sfree(ssh->savedhost);
 
     while (ssh->queuelen-- > 0)
diff --git a/ssh.h b/ssh.h
index 0b2d78ec..377c0568 100644
--- a/ssh.h
+++ b/ssh.h
@@ -874,12 +874,13 @@ void diagbn(char *prefix, Bignum md);
 #endif
 
 int dh_is_gex(const struct ssh_kex *kex);
-void *dh_setup_group(const struct ssh_kex *kex);
-void *dh_setup_gex(Bignum pval, Bignum gval);
-void dh_cleanup(void *);
-Bignum dh_create_e(void *, int nbits);
-const char *dh_validate_f(void *handle, Bignum f);
-Bignum dh_find_K(void *, Bignum f);
+struct dh_ctx;
+struct dh_ctx *dh_setup_group(const struct ssh_kex *kex);
+struct dh_ctx *dh_setup_gex(Bignum pval, Bignum gval);
+void dh_cleanup(struct dh_ctx *);
+Bignum dh_create_e(struct dh_ctx *, int nbits);
+const char *dh_validate_f(struct dh_ctx *, Bignum f);
+Bignum dh_find_K(struct dh_ctx *, Bignum f);
 
 int rsa_ssh1_encrypted(const Filename *filename, char **comment);
 int rsa_ssh1_loadpub(const Filename *filename, BinarySink *bs,
diff --git a/sshdh.c b/sshdh.c
index 1c27b021..c18da320 100644
--- a/sshdh.c
+++ b/sshdh.c
@@ -187,7 +187,7 @@ int dh_is_gex(const struct ssh_kex *kex)
 /*
  * Initialise DH for a standard group.
  */
-void *dh_setup_group(const struct ssh_kex *kex)
+struct dh_ctx *dh_setup_group(const struct ssh_kex *kex)
 {
     const struct dh_extra *extra = (const struct dh_extra *)kex->extra;
     struct dh_ctx *ctx = snew(struct dh_ctx);
@@ -200,7 +200,7 @@ void *dh_setup_group(const struct ssh_kex *kex)
 /*
  * Initialise DH for a server-supplied group.
  */
-void *dh_setup_gex(Bignum pval, Bignum gval)
+struct dh_ctx *dh_setup_gex(Bignum pval, Bignum gval)
 {
     struct dh_ctx *ctx = snew(struct dh_ctx);
     ctx->p = copybn(pval);
@@ -212,9 +212,8 @@ void *dh_setup_gex(Bignum pval, Bignum gval)
 /*
  * Clean up and free a context.
  */
-void dh_cleanup(void *handle)
+void dh_cleanup(struct dh_ctx *ctx)
 {
-    struct dh_ctx *ctx = (struct dh_ctx *)handle;
     freebn(ctx->x);
     freebn(ctx->e);
     freebn(ctx->p);
@@ -239,9 +238,8 @@ void dh_cleanup(void *handle)
  * Advances in Cryptology: Proceedings of Eurocrypt '96
  * Springer-Verlag, May 1996.
  */
-Bignum dh_create_e(void *handle, int nbits)
+Bignum dh_create_e(struct dh_ctx *ctx, int nbits)
 {
-    struct dh_ctx *ctx = (struct dh_ctx *)handle;
     int i;
 
     int nbytes;
@@ -295,9 +293,8 @@ Bignum dh_create_e(void *handle, int nbits)
  * they lead to obviously weak keys that even a passive eavesdropper
  * can figure out.)
  */
-const char *dh_validate_f(void *handle, Bignum f)
+const char *dh_validate_f(struct dh_ctx *ctx, Bignum f)
 {
-    struct dh_ctx *ctx = (struct dh_ctx *)handle;
     if (bignum_cmp(f, One) <= 0) {
         return "f value received is too small";
     } else {
@@ -313,9 +310,8 @@ const char *dh_validate_f(void *handle, Bignum f)
 /*
  * DH stage 2: given a number f, compute K = f^x mod p.
  */
-Bignum dh_find_K(void *handle, Bignum f)
+Bignum dh_find_K(struct dh_ctx *ctx, Bignum f)
 {
-    struct dh_ctx *ctx = (struct dh_ctx *)handle;
     Bignum ret;
     ret = modpow(f, ctx->x, ctx->p);
     return ret;