diff --git a/crypto.c b/crypto.c
index 0b7fb526..016912fc 100644
--- a/crypto.c
+++ b/crypto.c
@@ -1,3 +1,25 @@
+/*
+Serval Distributed Numbering Architecture (DNA)
+Copyright (C) 2010-2013 Paul Gardner-Stephen
+ 
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+ 
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+ 
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*/
+
+#include "crypto_sign_edwards25519sha512batch.h"
+#include "nacl/src/crypto_sign_edwards25519sha512batch_ref/ge.h"
+
 #include "serval.h"
 #include "overlay_address.h"
 #include "crypto.h"
@@ -95,3 +117,24 @@ int crypto_sign_message(struct subscriber *source, unsigned char *content, int b
   *content_len+=sig_length;
   return ret;
 }
+
+int _crypto_sign_compute_public_key(struct __sourceloc __whence,
+				    const unsigned char *skin,
+				    const unsigned char *pk)
+{
+  IN();
+
+  unsigned char h[64];
+  ge_p3 A;
+
+  crypto_hash_sha512(h,skin,32);
+  h[0] &= 248;
+  h[31] &= 63;
+  h[31] |= 64;
+
+  ge_scalarmult_base(&A,h);
+  ge_p3_tobytes((unsigned char *)pk,&A);
+
+  RETURN(0);
+  OUT();
+}
diff --git a/rhizome_crypto.c b/rhizome_crypto.c
index 98942314..b57297d2 100644
--- a/rhizome_crypto.c
+++ b/rhizome_crypto.c
@@ -17,9 +17,6 @@ along with this program; if not, write to the Free Software
 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */
 
-#include "crypto_sign_edwards25519sha512batch.h"
-#include "nacl/src/crypto_sign_edwards25519sha512batch_ref/ge.h"
-
 #include "serval.h"
 #include "conf.h"
 #include "str.h"
@@ -358,19 +355,10 @@ int rhizome_verify_bundle_privatekey(rhizome_manifest *m,
 {
   IN();
 
-  unsigned char h[64];
-  unsigned char pk[32];
-  ge_p3 A;
+  unsigned char pk[crypto_sign_edwards25519sha512batch_PUBLICKEYBYTES];
+  if (crypto_sign_compute_public_key(sk,pk)) RETURN(-1);
+
   int i;
-
-  crypto_hash_sha512(h,sk,32);
-  h[0] &= 248;
-  h[31] &= 63;
-  h[31] |= 64;
-
-  ge_scalarmult_base(&A,h);
-  ge_p3_tobytes(pk,&A);
-
   for (i = 0;i < 32;++i) 
     if (pkin[i] != pk[i]) {
       if (m&&sk==m->cryptoSignSecret&&pkin==m->cryptoSignPublic)
diff --git a/serval.h b/serval.h
index 6e229cc9..b987917d 100644
--- a/serval.h
+++ b/serval.h
@@ -842,4 +842,9 @@ int link_state_announce_links();
 
 int generate_nonce(unsigned char *nonce,int bytes);
 
+int _crypto_sign_compute_public_key(struct __sourceloc __whence,
+				    const unsigned char *skin,
+				    const unsigned char *pk);
+#define crypto_sign_compute_public_key(skin,pk) _crypto_sign_compute_public_key(__WHENCE__,skin,pk)
+
 #endif // __SERVALD_SERVALD_H