diff --git a/overlay_buffer.c b/overlay_buffer.c
index 47f23169..70f45a20 100644
--- a/overlay_buffer.c
+++ b/overlay_buffer.c
@@ -413,17 +413,15 @@ void _ob_append_packed_ui64(struct __sourceloc __whence, struct overlay_buffer *
 // make sure a range of bytes is valid for reading
 static int test_offset(struct overlay_buffer *b, size_t length)
 {
-  if (b->position + length > b->sizeLimit)
-    return -1;
-  if (b->position + length > b->allocSize)
-    return -1;
-  return 0;
+  assert(length != 0);
+  size_t off = b->position + length;
+  return off <= b->sizeLimit && off <= b->allocSize;
 }
 
 // next byte without advancing
 int ob_peek(struct overlay_buffer *b)
 {
-  if (test_offset(b, 1))
+  if (!test_offset(b, 1))
     return -1;
   return b->bytes[b->position];
 }
@@ -437,8 +435,8 @@ void ob_skip(struct overlay_buffer *b, unsigned n)
 const char *ob_get_str_ptr(struct overlay_buffer *b)
 {
   const char *ret = (const char*)(b->bytes + b->position);
-  off_t ofs=0;
-  while (test_offset(b, ofs)==0){
+  off_t ofs = 0;
+  while (test_offset(b, ofs + 1)) {
     if (ret[ofs]=='\0'){
       b->position+=ofs+1;
       return ret;
@@ -450,7 +448,7 @@ const char *ob_get_str_ptr(struct overlay_buffer *b)
 
 int ob_get_bytes(struct overlay_buffer *b, unsigned char *buff, size_t len)
 {
-  if (test_offset(b, len))
+  if (!test_offset(b, len))
     return -1;
   bcopy(b->bytes + b->position, buff, len);
   b->position+=len;
@@ -459,7 +457,7 @@ int ob_get_bytes(struct overlay_buffer *b, unsigned char *buff, size_t len)
 
 unsigned char * ob_get_bytes_ptr(struct overlay_buffer *b, size_t len)
 {
-  if (test_offset(b, len))
+  if (!test_offset(b, len))
     return NULL;
   unsigned char *ret = b->bytes + b->position;
   b->position+=len;
@@ -468,7 +466,7 @@ unsigned char * ob_get_bytes_ptr(struct overlay_buffer *b, size_t len)
 
 uint32_t ob_get_ui32(struct overlay_buffer *b)
 {
-  if (test_offset(b, 4))
+  if (!test_offset(b, 4))
     return 0xFFFFFFFF; // ... unsigned
   uint32_t ret = (unsigned)b->bytes[b->position] << 24
 	| b->bytes[b->position +1] << 16
@@ -480,7 +478,7 @@ uint32_t ob_get_ui32(struct overlay_buffer *b)
 
 uint32_t ob_get_ui32_rv(struct overlay_buffer *b)
 {
-  if (test_offset(b, 4))
+  if (!test_offset(b, 4))
     return 0xFFFFFFFF; // ... unsigned
   uint32_t ret = b->bytes[b->position]
 	| b->bytes[b->position +1] << 8
@@ -492,7 +490,7 @@ uint32_t ob_get_ui32_rv(struct overlay_buffer *b)
 
 uint64_t ob_get_ui64(struct overlay_buffer *b)
 {
-  if (test_offset(b, 8))
+  if (!test_offset(b, 8))
     return 0xFFFFFFFF; // ... unsigned
   uint64_t ret = (uint64_t)b->bytes[b->position] << 56
 	| (uint64_t)b->bytes[b->position +1] << 48
@@ -508,7 +506,7 @@ uint64_t ob_get_ui64(struct overlay_buffer *b)
 
 uint64_t ob_get_ui64_rv(struct overlay_buffer *b)
 {
-  if (test_offset(b, 8))
+  if (!test_offset(b, 8))
     return 0xFFFFFFFF; // ... unsigned
   uint64_t ret = (uint64_t)b->bytes[b->position]
 	| (uint64_t)b->bytes[b->position +1] << 8
@@ -524,7 +522,7 @@ uint64_t ob_get_ui64_rv(struct overlay_buffer *b)
 
 uint16_t ob_get_ui16(struct overlay_buffer *b)
 {
-  if (test_offset(b, 2))
+  if (!test_offset(b, 2))
     return 0xFFFF; // ... unsigned
   uint16_t ret = b->bytes[b->position] << 8
 	| b->bytes[b->position +1];
@@ -534,7 +532,7 @@ uint16_t ob_get_ui16(struct overlay_buffer *b)
 
 uint16_t ob_get_ui16_rv(struct overlay_buffer *b)
 {
-  if (test_offset(b, 2))
+  if (!test_offset(b, 2))
     return 0xFFFF; // ... unsigned
   uint16_t ret = b->bytes[b->position]
 	| b->bytes[b->position +1] << 8;
@@ -574,7 +572,7 @@ uint64_t ob_get_packed_ui64(struct overlay_buffer *b)
 
 int ob_get(struct overlay_buffer *b)
 {
-  if (test_offset(b, 1))
+  if (!test_offset(b, 1))
     return -1;
   return b->bytes[b->position++];
 }
diff --git a/overlay_mdp.c b/overlay_mdp.c
index 5e4f08fa..ba4ba1a9 100644
--- a/overlay_mdp.c
+++ b/overlay_mdp.c
@@ -1235,20 +1235,16 @@ static int mdp_process_identity_request(struct socket_address *client, struct md
       switch (request.type){
 	case TYPE_PIN:
 	  {
-	    while(1){
-	      const char *pin = ob_get_str_ptr(payload);
-	      if (!pin)
-		break;
+	    const char *pin;
+	    while ((pin = ob_get_str_ptr(payload)))
 	      keyring_release_identities_by_pin(keyring, pin);
-	    }
 	  }
 	  break;
 	case TYPE_SID:
-	  while(1){
-	    const sid_t *sid=(const sid_t*)ob_get_bytes_ptr(payload,SID_SIZE);
-	    if (sid==NULL)
-	      break;
-	    keyring_release_subscriber(keyring, sid);
+	  {
+	    const sid_t *sid;
+	    while ((sid = (const sid_t *)ob_get_bytes_ptr(payload, SID_SIZE)))
+	      keyring_release_subscriber(keyring, sid);
 	  }
 	  break;
 	default:
@@ -1257,20 +1253,20 @@ static int mdp_process_identity_request(struct socket_address *client, struct md
       }
       break;
     case ACTION_UNLOCK:
-      {
-	if (request.type!=TYPE_PIN){
+      switch (request.type){
+	case TYPE_PIN:
+	  {
+	    unsigned unlock_count=0;
+	    const char *pin;
+	    while ((pin = ob_get_str_ptr(payload)))
+	      unlock_count += keyring_enter_pin(keyring, pin);
+	    if (unlock_count && directory_service)
+	      directory_registration();
+	  }
+	  break;
+	default:
 	  mdp_reply_error(client, header);
 	  return WHY("Unknown request type");
-	}
-	unsigned unlock_count=0;
-	while(1){
-	  const char *pin = ob_get_str_ptr(payload);
-	  if (!pin)
-	    break;
-	  unlock_count += keyring_enter_pin(keyring, pin);
-	}
-	if (unlock_count && directory_service)
-	  directory_registration();
       }
       break;
     default:
@@ -1303,17 +1299,17 @@ static int mdp_search_identities(struct socket_address *client, struct mdp_heade
   
   while(1){
     if (value_len){
-      DEBUGF(mdprequests, "Looking for next %s tag & value", tag);
       if (!keyring_find_public_tag_value(&it, tag, value, value_len))
 	break;
+      DEBUGF(mdprequests, "found tag=%s value=%s", tag, value);
     }else if(tag){
-      DEBUGF(mdprequests, "Looking for next %s tag", tag);
       if (!keyring_find_public_tag(&it, tag, NULL, NULL))
 	break;
+      DEBUGF(mdprequests, "found tag=%s", tag);
     }else{
-      DEBUGF(mdprequests, "Looking for next identity");
       if (!keyring_next_identity(&it))
 	break;
+      DEBUGF(mdprequests, "found identity slot=%u SID=%s", it.identity->slot, alloca_tohex_sid_t(it.identity->subscriber->sid));
     }
     unsigned char reply_payload[1200];
     size_t ofs=0;
@@ -1578,6 +1574,7 @@ static void mdp_process_packet(struct socket_address *client, struct mdp_header
 	break;
       case MDP_IDENTITY:
 	DEBUGF(mdprequests, "Processing MDP_IDENTITY from %s", alloca_socket_address(client));
+	DEBUG_dump(mdprequests, "payload", payload->bytes, payload->sizeLimit);
 	mdp_process_identity_request(client, header, payload);
 	break;
       // seach unlocked identities