Fix pow (#417)

* fix pow

* only pow with nonse

app/src/main/java/com/bitchat/android/nostr/GeohashMessageHandler.kt

@@ -78,6 +78,7 @@ class GeohashMessageHandler(
                 if (isTeleportPresence) return@launch
 
                 val senderName = repo.displayNameForNostrPubkeyUI(event.pubkey)
+                val hasNonce = try { NostrProofOfWork.hasNonce(event) } catch (_: Exception) { false }
                 val msg = BitchatMessage(
                     id = event.id,
                     sender = senderName,
@@ -88,7 +89,9 @@ class GeohashMessageHandler(
                     senderPeerID = "nostr:${event.pubkey.take(8)}",
                     mentions = null,
                     channel = "#$subscribedGeohash",
-                    powDifficulty = try { NostrProofOfWork.calculateDifficulty(event.id).takeIf { it > 0 } } catch (_: Exception) { null }
+                    powDifficulty = try {
+                        if (hasNonce) NostrProofOfWork.calculateDifficulty(event.id).takeIf { it > 0 } else null
+                    } catch (_: Exception) { null }
                 )
                 withContext(Dispatchers.Main) { messageManager.addChannelMessage("geo:$subscribedGeohash", msg) }
             } catch (e: Exception) {

app/src/main/java/com/bitchat/android/nostr/NostrProofOfWork.kt

@@ -54,6 +54,12 @@ object NostrProofOfWork {
     fun validateDifficulty(event: NostrEvent, minimumDifficulty: Int): Boolean {
         if (minimumDifficulty <= 0) return true
         
+        // Require explicit nonce tag to recognize PoW per NIP-13 intent
+        if (!hasNonce(event)) {
+            Log.w(TAG, "Event ${event.id.take(16)}... missing nonce tag; treating as no PoW")
+            return false
+        }
+        
         val actualDifficulty = calculateDifficulty(event.id)
         val committedDifficulty = getCommittedDifficulty(event)