Implement password-protected rooms with encryption

- Room creators can set/remove passwords for their rooms
- Passwords are used to derive encryption keys via PBKDF2
- All messages in password-protected rooms are encrypted with AES-GCM
- Room protection status is announced to all peers
- Password and room data persists across app launches
- Visual lock indicators for password-protected rooms
- Password prompts when joining protected rooms
- Only room creators can modify password settings
- Encrypted messages show placeholder text if password is unknown

bitchat/Protocols/BinaryProtocol.swift

@@ -180,14 +180,14 @@ extension BitchatMessage {
         var data = Data()
         
         // Message format:
-        // - Flags: 1 byte (bit 0: isRelay, bit 1: isPrivate, bit 2: hasOriginalSender, bit 3: hasRecipientNickname, bit 4: hasSenderPeerID, bit 5: hasMentions, bit 6: hasVoiceNote)
+        // - Flags: 1 byte (bit 0: isRelay, bit 1: isPrivate, bit 2: hasOriginalSender, bit 3: hasRecipientNickname, bit 4: hasSenderPeerID, bit 5: hasMentions, bit 6: hasRoom, bit 7: isEncrypted)
         // - Timestamp: 8 bytes (seconds since epoch)
         // - ID length: 1 byte
         // - ID: variable
         // - Sender length: 1 byte
         // - Sender: variable
         // - Content length: 2 bytes
-        // - Content: variable
+        // - Content: variable (or encrypted content if isEncrypted)
         // Optional fields based on flags:
         // - Original sender length + data
         // - Recipient nickname length + data
@@ -203,6 +203,7 @@ extension BitchatMessage {
         if senderPeerID != nil { flags |= 0x10 }
         if mentions != nil && !mentions!.isEmpty { flags |= 0x20 }
         if room != nil { flags |= 0x40 }
+        if isEncrypted { flags |= 0x80 }
         
         data.append(flags)
         
@@ -229,8 +230,14 @@ extension BitchatMessage {
             data.append(0)
         }
         
-        // Content
-        if let contentData = content.data(using: .utf8) {
+        // Content or encrypted content
+        if isEncrypted, let encryptedContent = encryptedContent {
+            let length = UInt16(min(encryptedContent.count, 65535))
+            // Encode length as 2 bytes, big-endian
+            data.append(UInt8((length >> 8) & 0xFF))
+            data.append(UInt8(length & 0xFF))
+            data.append(encryptedContent.prefix(Int(length)))
+        } else if let contentData = content.data(using: .utf8) {
             let length = UInt16(min(contentData.count, 65535))
             // Encode length as 2 bytes, big-endian
             data.append(UInt8((length >> 8) & 0xFF))
@@ -301,6 +308,7 @@ extension BitchatMessage {
         let hasSenderPeerID = (flags & 0x10) != 0
         let hasMentions = (flags & 0x20) != 0
         let hasRoom = (flags & 0x40) != 0
+        let isEncrypted = (flags & 0x80) != 0
         
         // Timestamp
         guard offset + 8 <= dataCopy.count else { 
@@ -347,7 +355,19 @@ extension BitchatMessage {
         guard offset + contentLength <= dataCopy.count else { 
             return nil 
         }
-        let content = String(data: dataCopy[offset..<offset+contentLength], encoding: .utf8) ?? ""
+        
+        let content: String
+        let encryptedContent: Data?
+        
+        if isEncrypted {
+            // Content is encrypted, store as Data
+            encryptedContent = dataCopy[offset..<offset+contentLength]
+            content = ""  // Empty placeholder
+        } else {
+            // Normal string content
+            content = String(data: dataCopy[offset..<offset+contentLength], encoding: .utf8) ?? ""
+            encryptedContent = nil
+        }
         offset += contentLength
         
         // Optional fields
@@ -418,7 +438,9 @@ extension BitchatMessage {
             recipientNickname: recipientNickname,
             senderPeerID: senderPeerID,
             mentions: mentions,
-            room: room
+            room: room,
+            encryptedContent: encryptedContent,
+            isEncrypted: isEncrypted
         )
         return message
     }

bitchat/Protocols/BitchatProtocol.swift

@@ -69,6 +69,7 @@ enum MessageType: UInt8 {
     case fragmentStart = 0x05
     case fragmentContinue = 0x06
     case fragmentEnd = 0x07
+    case roomAnnounce = 0x08  // Announce password-protected room status
 }
 
 // Special recipient ID for broadcast messages
@@ -134,8 +135,10 @@ struct BitchatMessage: Codable, Equatable {
     let senderPeerID: String?
     let mentions: [String]?  // Array of mentioned nicknames
     let room: String?  // Room hashtag (e.g., "#general")
+    let encryptedContent: Data?  // For password-protected rooms
+    let isEncrypted: Bool  // Flag to indicate if content is encrypted
     
-    init(sender: String, content: String, timestamp: Date, isRelay: Bool, originalSender: String? = nil, isPrivate: Bool = false, recipientNickname: String? = nil, senderPeerID: String? = nil, mentions: [String]? = nil, room: String? = nil) {
+    init(sender: String, content: String, timestamp: Date, isRelay: Bool, originalSender: String? = nil, isPrivate: Bool = false, recipientNickname: String? = nil, senderPeerID: String? = nil, mentions: [String]? = nil, room: String? = nil, encryptedContent: Data? = nil, isEncrypted: Bool = false) {
         self.id = UUID().uuidString
         self.sender = sender
         self.content = content
@@ -147,6 +150,8 @@ struct BitchatMessage: Codable, Equatable {
         self.senderPeerID = senderPeerID
         self.mentions = mentions
         self.room = room
+        self.encryptedContent = encryptedContent
+        self.isEncrypted = isEncrypted
     }
 }
 
@@ -156,6 +161,8 @@ protocol BitchatDelegate: AnyObject {
     func didDisconnectFromPeer(_ peerID: String)
     func didUpdatePeerList(_ peers: [String])
     func didReceiveRoomLeave(_ room: String, from peerID: String)
+    func didReceivePasswordProtectedRoomAnnouncement(_ room: String, isProtected: Bool, creatorID: String?)
+    func decryptRoomMessage(_ encryptedContent: Data, room: String) -> String?
     
     // Optional method to check if a fingerprint belongs to a favorite peer
     func isFavorite(fingerprint: String) -> Bool
@@ -170,4 +177,13 @@ extension BitchatDelegate {
     func didReceiveRoomLeave(_ room: String, from peerID: String) {
         // Default empty implementation
     }
+    
+    func didReceivePasswordProtectedRoomAnnouncement(_ room: String, isProtected: Bool, creatorID: String?) {
+        // Default empty implementation
+    }
+    
+    func decryptRoomMessage(_ encryptedContent: Data, room: String) -> String? {
+        // Default returns nil (unable to decrypt)
+        return nil
+    }
 }