diff --git a/meerkat-common/src/main/java/meerkat/util/BulletinBoardUtils.java b/meerkat-common/src/main/java/meerkat/util/BulletinBoardUtils.java
index 35bcd9f..9f8b322 100644
--- a/meerkat-common/src/main/java/meerkat/util/BulletinBoardUtils.java
+++ b/meerkat-common/src/main/java/meerkat/util/BulletinBoardUtils.java
@@ -18,18 +18,17 @@ public class BulletinBoardUtils {
      *         signed by all given DigitalSignatures
      *
      * @param unsignedMessage BasicMessage
-     * @param signers collection of DigitalSignature which will sign the
-     *                UnsignedBulletinBoardMessage message
+     * @param signer DigitalSignature which will sign the UnsignedBulletinBoardMessage message
      * @return BulletinBoardMessage
      */
-    public static BulletinBoardMessage signBulletinBoardMessage(UnsignedBulletinBoardMessage unsignedMessage, Collection<DigitalSignature> signers) throws SignatureException {
+    public static BulletinBoardMessage signBulletinBoardMessage(UnsignedBulletinBoardMessage unsignedMessage,
+                                                                DigitalSignature signer) throws SignatureException {
         BulletinBoardMessage.Builder bulletinBoardMessage = BulletinBoardMessage.newBuilder();
         bulletinBoardMessage.setMsg(unsignedMessage);
-        for (DigitalSignature signer : signers) {
-            signer.updateContent(unsignedMessage);
-            Crypto.Signature signature = signer.sign();
-            bulletinBoardMessage.addSig(signature);
-        }
+        signer.updateContent(unsignedMessage);
+        Crypto.Signature signature = signer.sign();
+        bulletinBoardMessage.addSig(signature);
+
         return bulletinBoardMessage.build();
     }