Adjust PoW policy defaults (finalize 16/15/14 mapping)

bitchat.xcodeproj/project.pbxproj

@@ -7,6 +7,14 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		04657AB52E633C6A002D5BBE /* NostrPoW.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657AB42E633C6A002D5BBE /* NostrPoW.swift */; };
+		04657AB62E633C6A002D5BBE /* NostrPoW.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657AB42E633C6A002D5BBE /* NostrPoW.swift */; };
+		04657AB82E633C76002D5BBE /* PowPolicy.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657AB72E633C76002D5BBE /* PowPolicy.swift */; };
+		04657AB92E633C76002D5BBE /* PowPolicy.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657AB72E633C76002D5BBE /* PowPolicy.swift */; };
+		04657ABB2E633C94002D5BBE /* MiningAnimation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657ABA2E633C94002D5BBE /* MiningAnimation.swift */; };
+		04657ABC2E633C94002D5BBE /* MiningAnimation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657ABA2E633C94002D5BBE /* MiningAnimation.swift */; };
+		04657ABE2E633CA4002D5BBE /* NostrPoWTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657ABD2E633CA4002D5BBE /* NostrPoWTests.swift */; };
+		04657ABF2E633CA4002D5BBE /* NostrPoWTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 04657ABD2E633CA4002D5BBE /* NostrPoWTests.swift */; };
 		047502802E53A0FC0083520F /* FragmentationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0475027E2E53A0FC0083520F /* FragmentationTests.swift */; };
 		047502812E53A0FC0083520F /* FragmentationTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0475027E2E53A0FC0083520F /* FragmentationTests.swift */; };
 		047502872E5416250083520F /* Geohash.swift in Sources */ = {isa = PBXBuildFile; fileRef = 047502852E5416250083520F /* Geohash.swift */; };
@@ -197,6 +205,10 @@
 
 /* Begin PBXFileReference section */
 		03C57F452B55FD0FD8F51421 /* bitchatTests_macOS.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = bitchatTests_macOS.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
+		04657AB42E633C6A002D5BBE /* NostrPoW.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NostrPoW.swift; sourceTree = "<group>"; };
+		04657AB72E633C76002D5BBE /* PowPolicy.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PowPolicy.swift; sourceTree = "<group>"; };
+		04657ABA2E633C94002D5BBE /* MiningAnimation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MiningAnimation.swift; sourceTree = "<group>"; };
+		04657ABD2E633CA4002D5BBE /* NostrPoWTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NostrPoWTests.swift; sourceTree = "<group>"; };
 		0475027E2E53A0FC0083520F /* FragmentationTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = FragmentationTests.swift; sourceTree = "<group>"; };
 		047502852E5416250083520F /* Geohash.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Geohash.swift; sourceTree = "<group>"; };
 		047502862E5416250083520F /* LocationChannel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LocationChannel.swift; sourceTree = "<group>"; };
@@ -451,6 +463,7 @@
 		A55126E93155456CAA8D6656 /* Views */ = {
 			isa = PBXGroup;
 			children = (
+				04657ABA2E633C94002D5BBE /* MiningAnimation.swift */,
 				AA77BB13CC22DD33EE44FF57 /* VerificationViews.swift */,
 				047502B22E55FED60083520F /* GeohashPeopleList.swift */,
 				047502B32E55FED60083520F /* MeshPeerList.swift */,
@@ -489,8 +502,9 @@
 		C3D98EB3E1B455E321F519F4 /* bitchatTests */ = {
 			isa = PBXGroup;
 			children = (
-				048A4C2A2E5FCE0300162C4A /* GeohashBookmarksStoreTests.swift */,
 				D69A18D27F9A565FD6041E12 /* Info.plist */,
+				04657ABD2E633CA4002D5BBE /* NostrPoWTests.swift */,
+				048A4C2A2E5FCE0300162C4A /* GeohashBookmarksStoreTests.swift */,
 				047502912E547ACC0083520F /* LocationChannelsTests.swift */,
 				C272F137CE00FC5A96E0CC06 /* NostrProtocolTests.swift */,
 				980B109CBA72BC996455C62B /* BLEServiceTests.swift */,
@@ -526,6 +540,7 @@
 		D98A3186D7E4C72E35BDF7FE /* Services */ = {
 			isa = PBXGroup;
 			children = (
+				04657AB72E633C76002D5BBE /* PowPolicy.swift */,
 				048A4C272E5FCD6600162C4A /* GeohashBookmarksStore.swift */,
 				048A4BE62E5CCCC300162C4A /* TransportConfig.swift */,
 				AA77BB10CC22DD33EE44FF55 /* VerificationService.swift */,
@@ -550,6 +565,7 @@
 		E78C7F4B6769C0A72F5DE544 /* Nostr */ = {
 			isa = PBXGroup;
 			children = (
+				04657AB42E633C6A002D5BBE /* NostrPoW.swift */,
 				A1B2C3D44E5F60718293A4B4 /* XChaCha20Poly1305Compat.swift */,
 				049BD39B2E51DBD9001A566B /* NostrEmbeddedBitChat.swift */,
 				5F8043995007F0D84438EDD9 /* NostrIdentity.swift */,
@@ -792,15 +808,18 @@
 				749D8CF8A362B6CD0786782D /* NotificationService.swift in Sources */,
 				049BD3AF2E51ED60001A566B /* Transport.swift in Sources */,
 				E2DCF7817344F1CCDB8B7B2F /* SecureIdentityStateManager.swift in Sources */,
+				04657ABC2E633C94002D5BBE /* MiningAnimation.swift in Sources */,
 				049BD3A02E51DBF4001A566B /* Packets.swift in Sources */,
 				047502892E5416250083520F /* Geohash.swift in Sources */,
 				0475028A2E5416250083520F /* LocationChannel.swift in Sources */,
+				04657AB82E633C76002D5BBE /* PowPolicy.swift in Sources */,
 				049BD3A12E51DBF4001A566B /* PeerID.swift in Sources */,
 				049BD3942E4EC4F0001A566B /* PrivateChatManager.swift in Sources */,
 				049BD3952E4EC4F0001A566B /* AutocompleteService.swift in Sources */,
 				049BD3962E4EC4F0001A566B /* CommandProcessor.swift in Sources */,
 				D111988977C3BC246AB27FA4 /* SecureLogger.swift in Sources */,
 				8DE687D2EB5EB120868DBFB5 /* BLEService.swift in Sources */,
+				04657AB52E633C6A002D5BBE /* NostrPoW.swift in Sources */,
 				AA11BB22CC33DD44EE55FF66 /* MessageTextHelpers.swift in Sources */,
 				E0A1B2C3D4E5F6012345678B /* GeoRelayDirectory.swift in Sources */,
 			);
@@ -852,15 +871,18 @@
 				61C81ED5F679D5E973EE0C07 /* NotificationService.swift in Sources */,
 				049BD3AE2E51ED60001A566B /* Transport.swift in Sources */,
 				68C4BE564735F6E7915274A2 /* SecureIdentityStateManager.swift in Sources */,
+				04657ABB2E633C94002D5BBE /* MiningAnimation.swift in Sources */,
 				049BD3A22E51DBF4001A566B /* Packets.swift in Sources */,
 				047502872E5416250083520F /* Geohash.swift in Sources */,
 				047502882E5416250083520F /* LocationChannel.swift in Sources */,
+				04657AB92E633C76002D5BBE /* PowPolicy.swift in Sources */,
 				049BD3A32E51DBF4001A566B /* PeerID.swift in Sources */,
 				049BD3902E4EC4F0001A566B /* PrivateChatManager.swift in Sources */,
 				049BD3912E4EC4F0001A566B /* AutocompleteService.swift in Sources */,
 				049BD3922E4EC4F0001A566B /* CommandProcessor.swift in Sources */,
 				EC5241969D2550B97629EBD0 /* SecureLogger.swift in Sources */,
 				C165DD35BB8E9C327A3C2DA4 /* BLEService.swift in Sources */,
+				04657AB62E633C6A002D5BBE /* NostrPoW.swift in Sources */,
 				AA11BB22CC33DD44EE55FF67 /* MessageTextHelpers.swift in Sources */,
 				E0A1B2C3D4E5F6012345678C /* GeoRelayDirectory.swift in Sources */,
 			);
@@ -875,6 +897,7 @@
 				8F282E9CCA5AE1ECC001D2E4 /* IntegrationTests.swift in Sources */,
 				047502B12E55E8450083520F /* InputValidatorTests.swift in Sources */,
 				D727EA273CB214FC32612469 /* MockBluetoothMeshService.swift in Sources */,
+				04657ABF2E633CA4002D5BBE /* NostrPoWTests.swift in Sources */,
 				047502932E547ACC0083520F /* LocationChannelsTests.swift in Sources */,
 				048A4C2B2E5FCE0300162C4A /* GeohashBookmarksStoreTests.swift in Sources */,
 				6C803BF930E7E19BE6E99EAA /* MockBLEService.swift in Sources */,
@@ -898,6 +921,7 @@
 				686441ABC2AF83EE98E6ECF2 /* IntegrationTests.swift in Sources */,
 				047502B02E55E8450083520F /* InputValidatorTests.swift in Sources */,
 				8851F08D88C5B1DE7B9F55C6 /* MockBluetoothMeshService.swift in Sources */,
+				04657ABE2E633CA4002D5BBE /* NostrPoWTests.swift in Sources */,
 				047502922E547ACC0083520F /* LocationChannelsTests.swift in Sources */,
 				048A4C2C2E5FCE0300162C4A /* GeohashBookmarksStoreTests.swift in Sources */,
 				3849CA6D99B2D536636DF4A6 /* MockBLEService.swift in Sources */,

bitchat/Nostr/NostrPoW.swift

@@ -0,0 +1,96 @@
+import Foundation
+import CryptoKit
+import Security
+import Darwin
+
+/// NIP-13 Proof-of-Work utilities for Nostr events.
+/// - Counts leading zero bits and mines a nonce tag to meet a target.
+enum NostrPoW {
+    /// Table of leading zero bit counts for all 256 byte values.
+    private static let lzTable: [UInt8] = {
+        (0...255).map { v -> UInt8 in
+            var x = UInt8(v)
+            if x == 0 { return 8 }
+            var n: UInt8 = 0
+            while (x & 0x80) == 0 {
+                n &+= 1
+                x <<= 1
+            }
+            return n
+        }
+    }()
+
+    /// Count leading zero bits in a 32-byte hash.
+    static func leadingZeroBits(_ data: Data) -> Int {
+        var total = 0
+        for b in data {
+            let lz = Int(lzTable[Int(b)])
+            total += lz
+            if lz != 8 { break }
+        }
+        return total
+    }
+
+    /// Compute Nostr event id hash (SHA-256 over canonical serialization) for given fields.
+    private static func eventIDHash(pubkey: String, createdAt: Int, kind: Int, tags: [[String]], content: String) -> (hex: String, data: Data) {
+        let serialized: [Any] = [0, pubkey, createdAt, kind, tags, content]
+        let json = try! JSONSerialization.data(withJSONObject: serialized, options: [.withoutEscapingSlashes])
+        let digest = SHA256.hash(data: json)
+        let data = Data(digest)
+        let hex = data.map { String(format: "%02x", $0) }.joined()
+        return (hex, data)
+    }
+
+    /// Mine a NIP-13 nonce tag that satisfies the target leading-zero bits.
+    /// - Parameters:
+    ///   - pubkey: x-only hex pubkey (64-hex chars)
+    ///   - createdAt: seconds since epoch
+    ///   - kind: event kind
+    ///   - baseTags: existing tags (e.g., [ ["g", geohash], ["n", nickname], ... ])
+    ///   - content: event content
+    ///   - targetBits: required leading zero bits
+    ///   - startNonce: optional starting nonce (random if nil)
+    /// - Returns: (nonce, idHex)
+    static func mine(pubkey: String,
+                     createdAt: Int,
+                     kind: Int,
+                     baseTags: [[String]],
+                     content: String,
+                     targetBits: Int,
+                     startNonce: UInt64? = nil) -> (nonce: UInt64, idHex: String) {
+        var nonce: UInt64 = startNonce ?? randomNonce()
+        // Build a local tags buffer once to avoid reallocating unrelated tags
+        var tags = baseTags
+        tags.append(["nonce", "0", String(targetBits)])
+
+        var iter: UInt64 = 0
+        while true {
+            var solved = false
+            var idHexOut = ""
+            // Use an autorelease pool periodically to keep memory stable on iOS
+            autoreleasepool {
+                // Update nonce tag value (second element)
+                tags[tags.count - 1][1] = String(nonce)
+                let (idHex, idData) = eventIDHash(pubkey: pubkey, createdAt: createdAt, kind: kind, tags: tags, content: content)
+                if leadingZeroBits(idData) >= targetBits {
+                    solved = true
+                    idHexOut = idHex
+                }
+            }
+            if solved {
+                return (nonce, idHexOut)
+            }
+            nonce &+= 1
+            iter &+= 1
+            if iter & 0x3FFF == 0 { /* yield every ~16k iterations */ _ = sched_yield() }
+        }
+    }
+
+    private static func randomNonce() -> UInt64 {
+        var n: UInt64 = 0
+        withUnsafeMutableBytes(of: &n) { ptr in
+            _ = SecRandomCopyBytes(kSecRandomDefault, ptr.count, ptr.baseAddress!)
+        }
+        return n
+    }
+}

bitchat/Protocols/BitchatProtocol.swift

@@ -409,6 +409,8 @@ class BitchatMessage: Codable {
     let senderPeerID: String?
     let mentions: [String]?  // Array of mentioned nicknames
     var deliveryStatus: DeliveryStatus? // Delivery tracking
+    // Mining state for Nostr geohash PoW (UI hint: hide timestamp, animate)
+    var isMiningPow: Bool? // default nil/false
     
     // Cached formatted text (not included in Codable)
     private var _cachedFormattedText: [String: AttributedString] = [:]
@@ -421,13 +423,18 @@ class BitchatMessage: Codable {
         _cachedFormattedText["\(isDark)-\(isSelf)"] = text
     }
     
+    func clearCachedFormattedText() {
+        _cachedFormattedText.removeAll()
+    }
+    
     // Codable implementation
     enum CodingKeys: String, CodingKey {
         case id, sender, content, timestamp, isRelay, originalSender
         case isPrivate, recipientNickname, senderPeerID, mentions, deliveryStatus
+        case isMiningPow
     }
     
-    init(id: String? = nil, sender: String, content: String, timestamp: Date, isRelay: Bool, originalSender: String? = nil, isPrivate: Bool = false, recipientNickname: String? = nil, senderPeerID: String? = nil, mentions: [String]? = nil, deliveryStatus: DeliveryStatus? = nil) {
+    init(id: String? = nil, sender: String, content: String, timestamp: Date, isRelay: Bool, originalSender: String? = nil, isPrivate: Bool = false, recipientNickname: String? = nil, senderPeerID: String? = nil, mentions: [String]? = nil, deliveryStatus: DeliveryStatus? = nil, isMiningPow: Bool? = nil) {
         self.id = id ?? UUID().uuidString
         self.sender = sender
         self.content = content
@@ -439,6 +446,7 @@ class BitchatMessage: Codable {
         self.senderPeerID = senderPeerID
         self.mentions = mentions
         self.deliveryStatus = deliveryStatus ?? (isPrivate ? .sending : nil)
+        self.isMiningPow = isMiningPow
     }
 }
 
@@ -455,7 +463,8 @@ extension BitchatMessage: Equatable {
                lhs.recipientNickname == rhs.recipientNickname &&
                lhs.senderPeerID == rhs.senderPeerID &&
                lhs.mentions == rhs.mentions &&
-               lhs.deliveryStatus == rhs.deliveryStatus
+               lhs.deliveryStatus == rhs.deliveryStatus &&
+               (lhs.isMiningPow ?? false) == (rhs.isMiningPow ?? false)
     }
 }
 

bitchat/Services/PowPolicy.swift

@@ -0,0 +1,17 @@
+import Foundation
+
+/// Simple default policy for NIP-13 difficulty on geohash chats.
+/// Progressive by geohash precision; adjustable later by live activity.
+enum PowPolicy {
+    /// Determine target bits for a given geohash string.
+    /// Clamped to a sane range to keep UX responsive on phones.
+    static func requiredBits(forGeohash geohash: String) -> Int {
+        let precision = geohash.count
+        // Start at 13 and go down with higher precision (smaller areas)
+        switch precision {
+        case ...5: return 16
+        case 6:    return 15
+        default:   return 14
+        }
+    }
+}

bitchat/ViewModels/ChatViewModel.swift

@@ -796,6 +796,17 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             guard event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue else { return }
             if self.processedNostrEvents.contains(event.id) { return }
             self.processedNostrEvents.insert(event.id)
+            // PoW filter: require local difficulty for this geohash
+            let ghFromTag: String? = event.tags.first(where: { $0.first?.lowercased() == "g" && $0.count >= 2 })?.dropFirst().first
+            let ghValue = ghFromTag ?? ch.geohash
+            if let idData = Data(hexString: event.id) {
+                let powBits = NostrPoW.leadingZeroBits(idData)
+                let required = PowPolicy.requiredBits(forGeohash: ghValue)
+                if powBits < required {
+                    // Drop low PoW event
+                    return
+                }
+            }
             if let gh = self.currentGeohash,
                let myGeoIdentity = try? NostrIdentityBridge.deriveIdentity(forGeohash: gh),
                myGeoIdentity.publicKeyHex.lowercased() == event.pubkey.lowercased() {
@@ -813,8 +824,11 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             let key8 = "nostr:" + String(event.pubkey.prefix(TransportConfig.nostrShortKeyDisplayLength))
             self.nostrKeyMapping[key8] = event.pubkey
 
-            // Update participants last-seen for this pubkey
+            // Update participants last-seen for this pubkey with observed PoW bits
-            self.recordGeoParticipant(pubkeyHex: event.pubkey)
+            if let idData = Data(hexString: event.id) {
+                let powBits = NostrPoW.leadingZeroBits(idData)
+                self.recordGeoParticipant(pubkeyHex: event.pubkey, geohash: ch.geohash, powBits: powBits)
+            }
             
             // Track teleported tag (only our format ["t","teleport"]) for icon state
             let hasTeleportTag = event.tags.contains(where: { tag in
@@ -1320,7 +1334,11 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                 isPrivate: false,
                 recipientNickname: nil,
                 senderPeerID: localSenderPeerID,
-                mentions: mentions.isEmpty ? nil : mentions
+                mentions: mentions.isEmpty ? nil : mentions,
+                deliveryStatus: nil,
+                isMiningPow: {
+                    if case .location(_) = activeChannel { return true } else { return nil }
+                }()
             )
             
             // Add to main messages immediately for user feedback
@@ -1353,17 +1371,42 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             }
             
             if case .location(let ch) = activeChannel {
-                // Send to geohash channel via Nostr ephemeral
+                // Send to geohash channel via Nostr ephemeral with PoW
-                Task { @MainActor in
+                let msgID = message.id
+                let contentToSend = trimmed
+                Task {@MainActor in
                     do {
                         let identity = try NostrIdentityBridge.deriveIdentity(forGeohash: ch.geohash)
-                        let event = try NostrProtocol.createEphemeralGeohashEvent(
+                        let createdAt = Int(message.timestamp.timeIntervalSince1970)
-                            content: trimmed,
+                        var baseTags = [["g", ch.geohash]]
-                            geohash: ch.geohash,
+                        if !self.nickname.isEmpty { baseTags.append(["n", self.nickname]) }
-                            senderIdentity: identity,
+                        if LocationChannelManager.shared.teleported { baseTags.append(["t", "teleport"]) }
-                            nickname: self.nickname,
+                        let bits = PowPolicy.requiredBits(forGeohash: ch.geohash)
-                            teleported: LocationChannelManager.shared.teleported
+                        // Mine off the main thread
+                        let (nonce, _) = await withCheckedContinuation { (cont: CheckedContinuation<(UInt64, String), Never>) in
+                            DispatchQueue.global(qos: .utility).async {
+                                let res = NostrPoW.mine(pubkey: identity.publicKeyHex,
+                                                        createdAt: createdAt,
+                                                        kind: NostrProtocol.EventKind.ephemeralEvent.rawValue,
+                                                        baseTags: baseTags,
+                                                        content: contentToSend,
+                                                        targetBits: bits)
+                                cont.resume(returning: (res.nonce, res.idHex))
+                            }
+                        }
+                        // Build final event with nonce tag and sign
+                        var tags = baseTags
+                        tags.append(["nonce", String(nonce), String(bits)])
+                        var event = NostrEvent(
+                            pubkey: identity.publicKeyHex,
+                            createdAt: message.timestamp,
+                            kind: .ephemeralEvent,
+                            tags: tags,
+                            content: contentToSend
                         )
+                        let schnorrKey = try identity.schnorrSigningKey()
+                        event = try event.sign(with: schnorrKey)
+
                         let targetRelays = GeoRelayDirectory.shared.closestRelays(
                             toGeohash: ch.geohash,
                             count: TransportConfig.nostrGeoRelayCount
@@ -1373,12 +1416,22 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                         } else {
                             NostrRelayManager.shared.sendEvent(event, to: targetRelays)
                         }
-                        // Track ourselves as active participant
+                        // Track ourselves as active participant with PoW record
-                        self.recordGeoParticipant(pubkeyHex: identity.publicKeyHex)
+                        if let idData = Data(hexString: event.id) {
-                        SecureLogger.log("GeoTeleport: sent geo message pub=\(identity.publicKeyHex.prefix(8))… teleported=\(LocationChannelManager.shared.teleported)",
+                            let powBits = NostrPoW.leadingZeroBits(idData)
-                                        category: SecureLogger.session, level: .debug)
+                            self.recordGeoParticipant(pubkeyHex: identity.publicKeyHex, geohash: ch.geohash, powBits: powBits)
-                        // If we tagged this as teleported, also mark our pubkey in teleportedGeo for UI
+                        } else {
-                        // Only when not in our regional set (and regional list is known)
+                            self.recordGeoParticipant(pubkeyHex: identity.publicKeyHex)
+                        }
+                        SecureLogger.log("Geo: sent geo event id=\(event.id.prefix(12))… bits=\(bits) nonce=\(String(nonce))", category: SecureLogger.session, level: .debug)
+                        // Reveal timestamp / stop animation
+                        if let idx = self.messages.firstIndex(where: { $0.id == msgID }) {
+                            self.messages[idx].isMiningPow = false
+                            self.messages[idx].clearCachedFormattedText()
+                            // Trigger UI refresh so timestamp appears
+                            self.objectWillChange.send()
+                        }
+                        // If teleported and outside regional set, mark self teleported
                         let hasRegional = !LocationChannelManager.shared.availableChannels.isEmpty
                         let inRegional = LocationChannelManager.shared.availableChannels.contains { $0.geohash == ch.geohash }
                         if LocationChannelManager.shared.teleported && hasRegional && !inRegional {
@@ -1390,6 +1443,11 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                     } catch {
                         SecureLogger.log("❌ Failed to send geohash message: \(error)", category: SecureLogger.session, level: .error)
                         self.addSystemMessage("failed to send to location channel")
+                        if let idx = self.messages.firstIndex(where: { $0.id == msgID }) {
+                            self.messages[idx].isMiningPow = false
+                            self.messages[idx].clearCachedFormattedText()
+                            self.objectWillChange.send()
+                        }
                     }
                 }
             } else {
@@ -1491,6 +1549,16 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             // Deduplicate
             if self.processedNostrEvents.contains(event.id) { return }
             self.recordProcessedEvent(event.id)
+            // PoW filter for geohash events
+            let ghFromTag: String? = event.tags.first(where: { $0.first?.lowercased() == "g" && $0.count >= 2 })?.dropFirst().first
+            let ghValue = ghFromTag ?? ch.geohash
+            if let idData = Data(hexString: event.id) {
+                let powBits = NostrPoW.leadingZeroBits(idData)
+                let required = PowPolicy.requiredBits(forGeohash: ghValue)
+                if powBits < required {
+                    return
+                }
+            }
             // Log incoming tags for diagnostics
             let tagSummary = event.tags.map { "[" + $0.joined(separator: ",") + "]" }.joined(separator: ",")
             SecureLogger.log("GeoTeleport: recv pub=\(event.pubkey.prefix(8))… tags=\(tagSummary)",
@@ -1537,8 +1605,11 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             self.nostrKeyMapping[key16] = event.pubkey
             let key8 = "nostr:" + String(event.pubkey.prefix(TransportConfig.nostrShortKeyDisplayLength))
             self.nostrKeyMapping[key8] = event.pubkey
-            // Update participants last-seen for this pubkey
+            // Update participants last-seen for this pubkey with observed PoW bits
-            self.recordGeoParticipant(pubkeyHex: event.pubkey)
+            if let idData = Data(hexString: event.id) {
+                let powBits = NostrPoW.leadingZeroBits(idData)
+                self.recordGeoParticipant(pubkeyHex: event.pubkey, geohash: ch.geohash, powBits: powBits)
+            }
             
             let senderName = self.displayNameForNostrPubkey(event.pubkey)
             let content = event.content
@@ -1723,6 +1794,24 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         }
     }
 
+    // Track last observed PoW bits per participant per geohash
+    private var geoParticipantPowBits: [String: [String: Int]] = [:] // geohash -> (pubkeyLower -> bits)
+
+    private func recordGeoParticipant(pubkeyHex: String, geohash: String, powBits: Int?) {
+        let key = pubkeyHex.lowercased()
+        var map = geoParticipants[geohash] ?? [:]
+        map[key] = Date()
+        geoParticipants[geohash] = map
+        if let bits = powBits {
+            var powMap = geoParticipantPowBits[geohash] ?? [:]
+            powMap[key] = bits
+            geoParticipantPowBits[geohash] = powMap
+        }
+        if currentGeohash == geohash {
+            refreshGeohashPeople()
+        }
+    }
+
     private func refreshGeohashPeople() {
         guard let gh = currentGeohash else { geohashPeople = []; return }
         let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
@@ -1731,6 +1820,17 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         map = map.filter { $0.value >= cutoff }
         // Remove blocked Nostr pubkeys
         map = map.filter { !SecureIdentityStateManager.shared.isNostrBlocked(pubkeyHexLowercased: $0.key) }
+        // Enforce PoW threshold for peer list as well
+        let required = PowPolicy.requiredBits(forGeohash: gh)
+        let myHex: String? = (try? NostrIdentityBridge.deriveIdentity(forGeohash: gh))?.publicKeyHex.lowercased()
+        let powMap = geoParticipantPowBits[gh] ?? [:]
+        map = map.filter { (pub, _) in
+            if let bits = powMap[pub] { return bits >= required }
+            // Always allow self even if no PoW record yet
+            if let me = myHex, pub == me { return true }
+            // Otherwise, if no PoW info, hide until we see an acceptable event
+            return false
+        }
         geoParticipants[gh] = map
         // Build display list
         let people = map
@@ -1761,9 +1861,17 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
     func visibleGeohashPeople() -> [GeoPerson] {
         guard let gh = currentGeohash else { return [] }
         let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
+        let required = PowPolicy.requiredBits(forGeohash: gh)
+        let myHex: String? = (try? NostrIdentityBridge.deriveIdentity(forGeohash: gh))?.publicKeyHex.lowercased()
+        let powMap = geoParticipantPowBits[gh] ?? [:]
         let map = (geoParticipants[gh] ?? [:])
             .filter { $0.value >= cutoff }
             .filter { !SecureIdentityStateManager.shared.isNostrBlocked(pubkeyHexLowercased: $0.key) }
+            .filter { (pub, _) in
+                if let bits = powMap[pub] { return bits >= required }
+                if let me = myHex, pub == me { return true }
+                return false
+            }
         let people = map
             .map { (pub, seen) in GeoPerson(id: pub, displayName: displayNameForNostrPubkey(pub), lastSeen: seen) }
             .sorted { $0.lastSeen > $1.lastSeen }
@@ -1865,6 +1973,12 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             NostrRelayManager.shared.subscribe(filter: filter, id: subID, relayUrls: subRelays) { [weak self] event in
                 guard let self = self else { return }
                 guard event.kind == NostrProtocol.EventKind.ephemeralEvent.rawValue else { return }
+                // Enforce PoW for sampled geohashes too
+                if let idData = Data(hexString: event.id) {
+                    let powBits = NostrPoW.leadingZeroBits(idData)
+                    let required = PowPolicy.requiredBits(forGeohash: gh)
+                    if powBits < required { return }
+                }
                 // Compute current participant count (5-minute window) BEFORE updating with this event
                 let cutoff = Date().addingTimeInterval(-TransportConfig.uiRecentCutoffFiveMinutesSeconds)
                 let existingCount: Int = {
@@ -1872,7 +1986,12 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                     return map.values.filter { $0 >= cutoff }.count
                 }()
                 // Update participants for this specific geohash
-                self.recordGeoParticipant(pubkeyHex: event.pubkey, geohash: gh)
+                if let idData = Data(hexString: event.id) {
+                    let powBits = NostrPoW.leadingZeroBits(idData)
+                    self.recordGeoParticipant(pubkeyHex: event.pubkey, geohash: gh, powBits: powBits)
+                } else {
+                    self.recordGeoParticipant(pubkeyHex: event.pubkey, geohash: gh)
+                }
                 // Notify only on rising-edge: previously zero people, now someone sends a chat
                 let content = event.content.trimmingCharacters(in: .whitespacesAndNewlines)
                 guard !content.isEmpty else { return }
@@ -2667,27 +2786,7 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
                 meshService.sendMessage(screenshotMessage, mentions: [])
             case .location(let ch):
                 Task { @MainActor in
-                    do {
+                    await mineAndSendGeohashEvent(content: screenshotMessage, geohash: ch.geohash, nickname: self.nickname, teleported: LocationChannelManager.shared.teleported, createdAt: Date())
-                        let identity = try NostrIdentityBridge.deriveIdentity(forGeohash: ch.geohash)
-                        let event = try NostrProtocol.createEphemeralGeohashEvent(
-                            content: screenshotMessage,
-                            geohash: ch.geohash,
-                            senderIdentity: identity,
-                            nickname: self.nickname,
-                            teleported: LocationChannelManager.shared.teleported
-                        )
-                        let targetRelays = GeoRelayDirectory.shared.closestRelays(toGeohash: ch.geohash, count: 5)
-                        if targetRelays.isEmpty {
-                            SecureLogger.log("Geo: no geohash relays available for \(ch.geohash); not sending", category: SecureLogger.session, level: .warning)
-                        } else {
-                            NostrRelayManager.shared.sendEvent(event, to: targetRelays)
-                        }
-                        // Track ourselves as active participant
-                        self.recordGeoParticipant(pubkeyHex: identity.publicKeyHex)
-                    } catch {
-                        SecureLogger.log("❌ Failed to send geohash screenshot message: \(error)", category: SecureLogger.session, level: .error)
-                        self.addSystemMessage("failed to send to location channel")
-                    }
                 }
             }
             
@@ -3138,6 +3237,59 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         return processedContent
     }
 
+    // MARK: - Helpers for mining UI
+    @MainActor
+    func isSelfMessage(_ message: BitchatMessage) -> Bool {
+        let isSelf: Bool = {
+            if let spid = message.senderPeerID {
+                if spid == meshService.myPeerID { return true }
+                if case .location(let ch) = activeChannel,
+                   let id = try? NostrIdentityBridge.deriveIdentity(forGeohash: ch.geohash) {
+                    if spid.hasPrefix("nostr:") || spid.hasPrefix("nostr_") {
+                        let bare: String = spid.hasPrefix("nostr:") ? String(spid.dropFirst(6)) : String(spid.dropFirst(6))
+                        return bare.lowercased().hasPrefix(id.publicKeyHex.lowercased().prefix(TransportConfig.nostrShortKeyDisplayLength))
+                    }
+                }
+                return spid == meshService.myPeerID
+            }
+            if message.sender == nickname { return true }
+            if message.sender.hasPrefix(nickname + "#") { return true }
+            return false
+        }()
+        return isSelf
+    }
+
+    @MainActor
+    func baseColorForMessage(_ message: BitchatMessage, colorScheme: ColorScheme) -> Color {
+        let isDark = colorScheme == .dark
+        return isSelfMessage(message) ? .orange : peerColor(for: message, isDark: isDark)
+    }
+
+    @MainActor
+    func formatSenderPrefix(_ message: BitchatMessage, colorScheme: ColorScheme) -> AttributedString {
+        let isSelf = isSelfMessage(message)
+        let isDark = colorScheme == .dark
+        let baseColor: Color = isSelf ? .orange : peerColor(for: message, isDark: isDark)
+        let (baseName, suffix) = splitSuffix(from: message.sender)
+        var senderStyle = AttributeContainer()
+        senderStyle.foregroundColor = baseColor
+        let fontWeight: Font.Weight = isSelf ? .bold : .medium
+        senderStyle.font = .system(size: 14, weight: fontWeight, design: .monospaced)
+        if let spid = message.senderPeerID, let url = URL(string: "bitchat://user/\(spid.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) ?? spid)") {
+            senderStyle.link = url
+        }
+        var prefix = AttributedString()
+        prefix.append(AttributedString("<@").mergingAttributes(senderStyle))
+        prefix.append(AttributedString(baseName).mergingAttributes(senderStyle))
+        if !suffix.isEmpty {
+            var suffixStyle = senderStyle
+            suffixStyle.foregroundColor = baseColor.opacity(0.6)
+            prefix.append(AttributedString(suffix).mergingAttributes(suffixStyle))
+        }
+        prefix.append(AttributedString("> ").mergingAttributes(senderStyle))
+        return prefix
+    }
+    
     @MainActor
     func formatMessageAsText(_ message: BitchatMessage, colorScheme: ColorScheme) -> AttributedString {
         // Determine if this message was sent by self (mesh, geo, or DM)
@@ -3443,12 +3595,15 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
             }
             }
             
-            // Add timestamp at the end (smaller, light grey)
+            // Add timestamp at the end (hide while PoW mining)
-            let timestamp = AttributedString(" [\(formatTimestamp(message.timestamp))]")
+            let hideTimestamp = (message.isMiningPow ?? false)
-            var timestampStyle = AttributeContainer()
+            if !hideTimestamp {
-            timestampStyle.foregroundColor = Color.gray.opacity(0.7)
+                let timestamp = AttributedString(" [\(formatTimestamp(message.timestamp))]")
-            timestampStyle.font = .system(size: 10, design: .monospaced)
+                var timestampStyle = AttributeContainer()
-            result.append(timestamp.mergingAttributes(timestampStyle))
+                timestampStyle.foregroundColor = Color.gray.opacity(0.7)
+                timestampStyle.font = .system(size: 10, design: .monospaced)
+                result.append(timestamp.mergingAttributes(timestampStyle))
+            }
         } else {
             // System message
             var contentStyle = AttributeContainer()
@@ -4883,24 +5038,7 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
     func sendPublicRaw(_ content: String) {
         if case .location(let ch) = activeChannel {
             Task { @MainActor in
-                do {
+                await mineAndSendGeohashEvent(content: content, geohash: ch.geohash, nickname: self.nickname, teleported: LocationChannelManager.shared.teleported, createdAt: Date())
-                    let identity = try NostrIdentityBridge.deriveIdentity(forGeohash: ch.geohash)
-                    let event = try NostrProtocol.createEphemeralGeohashEvent(
-                        content: content,
-                        geohash: ch.geohash,
-                        senderIdentity: identity,
-                        nickname: self.nickname,
-                        teleported: LocationChannelManager.shared.teleported
-                    )
-                    let targetRelays = GeoRelayDirectory.shared.closestRelays(toGeohash: ch.geohash, count: 5)
-                    if targetRelays.isEmpty {
-                        NostrRelayManager.shared.sendEvent(event)
-                    } else {
-                        NostrRelayManager.shared.sendEvent(event, to: targetRelays)
-                    }
-                } catch {
-                    SecureLogger.log("❌ Failed to send geohash raw message: \(error)", category: SecureLogger.session, level: .error)
-                }
             }
             return
         }
@@ -4908,6 +5046,49 @@ class ChatViewModel: ObservableObject, BitchatDelegate {
         meshService.sendMessage(content, mentions: [])
     }
 
+    // MARK: - Geohash PoW helper for system/raw messages
+    @MainActor
+    private func mineAndSendGeohashEvent(content: String, geohash: String, nickname: String, teleported: Bool, createdAt: Date) async {
+        do {
+            let identity = try NostrIdentityBridge.deriveIdentity(forGeohash: geohash)
+            let createdAtSecs = Int(createdAt.timeIntervalSince1970)
+            var baseTags = [["g", geohash]]
+            if !nickname.isEmpty { baseTags.append(["n", nickname]) }
+            if teleported { baseTags.append(["t", "teleport"]) }
+            let bits = PowPolicy.requiredBits(forGeohash: geohash)
+            let (nonce, _) = await withCheckedContinuation { (cont: CheckedContinuation<(UInt64, String), Never>) in
+                DispatchQueue.global(qos: .utility).async {
+                    let res = NostrPoW.mine(pubkey: identity.publicKeyHex,
+                                            createdAt: createdAtSecs,
+                                            kind: NostrProtocol.EventKind.ephemeralEvent.rawValue,
+                                            baseTags: baseTags,
+                                            content: content,
+                                            targetBits: bits)
+                    cont.resume(returning: (res.nonce, res.idHex))
+                }
+            }
+            var tags = baseTags
+            tags.append(["nonce", String(nonce), String(bits)])
+            var event = NostrEvent(
+                pubkey: identity.publicKeyHex,
+                createdAt: createdAt,
+                kind: .ephemeralEvent,
+                tags: tags,
+                content: content
+            )
+            let key = try identity.schnorrSigningKey()
+            event = try event.sign(with: key)
+            let relays = GeoRelayDirectory.shared.closestRelays(toGeohash: geohash, count: TransportConfig.nostrGeoRelayCount)
+            if relays.isEmpty {
+                NostrRelayManager.shared.sendEvent(event)
+            } else {
+                NostrRelayManager.shared.sendEvent(event, to: relays)
+            }
+        } catch {
+            SecureLogger.log("❌ GeoPoW: failed to send event: \(error)", category: SecureLogger.session, level: .error)
+        }
+    }
+    
     // MARK: - Simplified Nostr Integration (Inlined from MessageRouter)
     
     //

bitchat/Views/ContentView.swift

@@ -303,10 +303,21 @@ struct ContentView: View {
                                     HStack(alignment: .top, spacing: 0) {
                                         let isLong = (message.content.count > TransportConfig.uiLongMessageLengthThreshold || message.content.hasVeryLongToken(threshold: TransportConfig.uiVeryLongTokenThreshold)) && cashuTokens.isEmpty
                                         let isExpanded = expandedMessageIDs.contains(message.id)
-                                        Text(viewModel.formatMessageAsText(message, colorScheme: colorScheme))
+                                        let formatted = viewModel.formatMessageAsText(message, colorScheme: colorScheme)
-                                            .fixedSize(horizontal: false, vertical: true)
+                                        let prefixAttr = viewModel.formatSenderPrefix(message, colorScheme: colorScheme)
+                                        let baseColor = viewModel.baseColorForMessage(message, colorScheme: colorScheme)
+                                        let isSelfMsg = viewModel.isSelfMessage(message)
+                                        if (message.isMiningPow ?? false) {
+                                            // Single Text combines prefix + animated body, so wrapping matches final layout
+                                            CombinedMiningText(prefix: prefixAttr, original: message.content, color: baseColor, isSelf: isSelfMsg)
                                             .lineLimit(isLong && !isExpanded ? TransportConfig.uiLongMessageLineLimit : nil)
                                             .frame(maxWidth: .infinity, alignment: .leading)
+                                        } else {
+                                            Text(formatted)
+                                                .fixedSize(horizontal: false, vertical: true)
+                                                .lineLimit(isLong && !isExpanded ? TransportConfig.uiLongMessageLineLimit : nil)
+                                                .frame(maxWidth: .infinity, alignment: .leading)
+                                        }
                                         
                                         // Delivery status indicator for private messages
                                         if message.isPrivate && message.sender == viewModel.nickname,
@@ -1387,6 +1398,53 @@ struct ContentView: View {
     
 }
 
+// MARK: - Mining UI helpers (local to ensure inclusion in target)
+fileprivate struct CombinedMiningText: View {
+    let prefix: AttributedString
+    let original: String
+    let color: Color
+    let isSelf: Bool
+    let fontSize: CGFloat = 14
+    let interval: TimeInterval = 0.06
+    @State private var display: String = ""
+    @State private var timer: Timer? = nil
+
+    private let charset: [Character] = Array("abcdefghijklmnopqrstuvwxyz0123456789@#$%&*+-")
+
+    var body: some View {
+        Text(combinedAttributed)
+            .fixedSize(horizontal: false, vertical: true)
+            .onAppear {
+                display = scramble(original)
+                timer?.invalidate()
+                timer = Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { _ in
+                    display = scramble(original)
+                }
+            }
+            .onDisappear { timer?.invalidate(); timer = nil }
+    }
+
+    private var combinedAttributed: AttributedString {
+        var res = AttributedString()
+        res.append(prefix)
+        var style = AttributeContainer()
+        style.foregroundColor = color
+        style.font = .system(size: fontSize, weight: isSelf ? .bold : .regular, design: .monospaced)
+        res.append(AttributedString(display).mergingAttributes(style))
+        return res
+    }
+
+    private func scramble(_ s: String) -> String {
+        var out = String()
+        out.reserveCapacity(s.count)
+        for ch in s {
+            if ch.isWhitespace || ch.isNewline { out.append(ch); continue }
+            out.append(charset.randomElement() ?? ch)
+        }
+        return out
+    }
+}
+
 // MARK: - Helper Views
 
 // Rounded payment chip button

bitchat/Views/MiningAnimation.swift

@@ -0,0 +1,87 @@
+import SwiftUI
+
+/// Mining body animation: scramble characters (matrix-like) until PoW completes.
+struct MiningScrambleText: View {
+    let original: String
+    let color: Color
+    let isSelf: Bool
+    let fontSize: CGFloat = 14
+    let interval: TimeInterval = 0.06
+    @State private var display: String = ""
+    @State private var timer: Timer? = nil
+
+    private let charset: [Character] = Array("abcdefghijklmnopqrstuvwxyz0123456789@#$%&*+-")
+
+    var body: some View {
+        Text(display)
+            .font(.system(size: fontSize, weight: isSelf ? .bold : .regular, design: .monospaced))
+            .foregroundColor(color)
+            .onAppear {
+                display = scramble(original)
+                timer?.invalidate()
+                timer = Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { _ in
+                    display = scramble(original)
+                }
+            }
+            .onDisappear {
+                timer?.invalidate(); timer = nil
+            }
+}
+
+/// Combined prefix+body single-Text variant to ensure identical wrapping
+struct MiningCombinedText: View {
+    let prefix: AttributedString
+    let original: String
+    let color: Color
+    let isSelf: Bool
+    let fontSize: CGFloat = 14
+    let interval: TimeInterval = 0.06
+    @State private var display: String = ""
+    @State private var timer: Timer? = nil
+
+    private let charset: [Character] = Array("abcdefghijklmnopqrstuvwxyz0123456789@#$%&*+-")
+
+    var body: some View {
+        Text(combinedAttributed)
+            .fixedSize(horizontal: false, vertical: true)
+            .onAppear {
+                display = scramble(original)
+                timer?.invalidate()
+                timer = Timer.scheduledTimer(withTimeInterval: interval, repeats: true) { _ in
+                    display = scramble(original)
+                }
+            }
+            .onDisappear { timer?.invalidate(); timer = nil }
+    }
+
+    private var combinedAttributed: AttributedString {
+        var res = AttributedString()
+        res.append(prefix)
+        var style = AttributeContainer()
+        style.foregroundColor = color
+        style.font = .system(size: fontSize, weight: isSelf ? .bold : .regular, design: .monospaced)
+        res.append(AttributedString(display).mergingAttributes(style))
+        return res
+    }
+
+    private func scramble(_ s: String) -> String {
+        var out = String()
+        out.reserveCapacity(s.count)
+        for ch in s {
+            if ch.isWhitespace || ch.isNewline { out.append(ch); continue }
+            out.append(charset.randomElement() ?? ch)
+        }
+        return out
+    }
+}
+
+    private func scramble(_ s: String) -> String {
+        var out = String()
+        out.reserveCapacity(s.count)
+        for ch in s {
+            if ch.isWhitespace || ch.isNewline { out.append(ch); continue }
+            out.append(charset.randomElement() ?? ch)
+        }
+        return out
+    }
+}

bitchatTests/Info.plist

@@ -2,17 +2,17 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
-    <key>CFBundleIdentifier</key>
+	<key>CFBundleIdentifier</key>
-    <string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
-    <key>CFBundleInfoDictionaryVersion</key>
+	<key>CFBundleInfoDictionaryVersion</key>
-    <string>6.0</string>
+	<string>6.0</string>
-    <key>CFBundleName</key>
+	<key>CFBundleName</key>
-    <string>$(PRODUCT_NAME)</string>
+	<string>$(PRODUCT_NAME)</string>
-    <key>CFBundlePackageType</key>
+	<key>CFBundlePackageType</key>
-    <string>$(PRODUCT_BUNDLE_PACKAGE_TYPE)</string>
+	<string>$(PRODUCT_BUNDLE_PACKAGE_TYPE)</string>
-    <key>CFBundleShortVersionString</key>
+	<key>CFBundleShortVersionString</key>
-    <string>1.0</string>
+	<string>1.0</string>
-    <key>CFBundleVersion</key>
+	<key>CFBundleVersion</key>
-    <string>1</string>
+	<string>1</string>
 </dict>
 </plist>

bitchatTests/NostrPoWTests.swift

@@ -0,0 +1,32 @@
+import XCTest
+import CryptoKit
+@testable import bitchat
+
+final class NostrPoWTests: XCTestCase {
+    func testLeadingZeroBits() {
+        // 0x00 -> 8, 0x00 -> 8, 0xF0 -> 0 leading zeros
+        let data = Data([0x00, 0x00, 0xF0]) + Data(repeating: 0x00, count: 29)
+        let lz = NostrPoW.leadingZeroBits(data)
+        XCTAssertEqual(lz, 16)
+    }
+
+    func testMineLowDifficulty() {
+        let pubkey = String(repeating: "a", count: 64)
+        let createdAt = Int(Date().timeIntervalSince1970)
+        let kind = 20000
+        let tags = [["g", "u4pruydqqvj"]]
+        let content = "hello"
+        let targetBits = 8 // keep it very low for test speed
+        let (nonce, idHex) = NostrPoW.mine(pubkey: pubkey, createdAt: createdAt, kind: kind, baseTags: tags, content: content, targetBits: targetBits)
+        XCTAssertGreaterThan(nonce, 0)
+        // Verify difficulty
+        let powTags = tags + [["nonce", String(nonce), String(targetBits)]]
+        // Recompute ID
+        let serialized: [Any] = [0, pubkey, createdAt, kind, powTags, content]
+        let json = try! JSONSerialization.data(withJSONObject: serialized, options: [.withoutEscapingSlashes])
+        let digest = CryptoKit.SHA256.hash(data: json)
+        let idData = Data(digest)
+        XCTAssertEqual(idHex.count, 64)
+        XCTAssertGreaterThanOrEqual(NostrPoW.leadingZeroBits(idData), targetBits)
+    }
+}