support # channels

src/components/ConfigContext.tsx

@@ -1,6 +1,6 @@
 "use client";
 import React, { createContext, useContext, useState, useEffect, useRef, useLayoutEffect, ReactNode } from "react";
-import { getChannelIdFromKey } from "@/lib/meshcore";
+import { getChannelIdFromKey, deriveKeyFromChannelName } from "@/lib/meshcore";
 import { getRegionFriendlyNames } from "@/lib/regions";
 import Modal from "./Modal";
 
@@ -353,7 +353,19 @@ function MeshcoreKeyModal({ config, setConfig, onClose }: { config: Config, setC
                   value={key.channelName}
                   onChange={e => {
                     const updated = [...(config.meshcoreKeys || [])];
-                    updated[idx] = { ...updated[idx], channelName: e.target.value };
+                    const newChannelName = e.target.value;
+                    const updatedKey = { ...updated[idx], channelName: newChannelName };
+                    
+                    // Auto-populate private key for # channels
+                    if (newChannelName.startsWith('#') && newChannelName.length > 1) {
+                      try {
+                        updatedKey.privateKey = deriveKeyFromChannelName(newChannelName);
+                      } catch (error) {
+                        // If derivation fails, leave the key as is
+                      }
+                    }
+                    
+                    updated[idx] = updatedKey;
                     setConfig({ ...config, meshcoreKeys: updated });
                   }}
                 />
@@ -373,7 +385,7 @@ function MeshcoreKeyModal({ config, setConfig, onClose }: { config: Config, setC
                 <input
                   className={`flex-1 p-1 border rounded font-mono ${keyError ? 'border-red-500' : ''}`}
                   type="text"
-                  placeholder="Base64 or Hex Private Key"
+                  placeholder="Base64 or Hex Private Key (auto-filled for # channels)"
                   value={key.privateKey}
                   onChange={e => {
                     const updated = [...(config.meshcoreKeys || [])];

src/lib/meshcore.ts

@@ -1,6 +1,31 @@
 import { createHash, createHmac } from "crypto";
 import aesjs from "aes-js";
 
+/**
+ * Derives a 128-bit encryption key from a channel name that starts with '#'.
+ * Applies filtering: converts to lowercase and keeps only a-z, 0-9, and hyphen.
+ * Uses SHA256 hash of the filtered channel name (including '#') as ASCII bytes, 
+ * then truncates to first 128 bits (16 bytes) and returns as hex.
+ */
+export function deriveKeyFromChannelName(channelName: string): string {
+  if (!channelName.startsWith('#')) {
+    throw new Error('Channel name must start with #');
+  }
+  
+  // Apply filtering: lowercase and keep only a-z, 0-9, hyphen
+  const filteredName = '#' + channelName.slice(1)
+    .toLowerCase()
+    .replace(/[^a-z0-9-]/g, '');
+  
+  // Convert filtered channel name to ASCII bytes and hash with SHA256
+  const nameBytes = Buffer.from(filteredName, 'ascii');
+  const hash = createHash('sha256').update(nameBytes).digest();
+  
+  // Truncate to first 128 bits (16 bytes) and return as hex
+  const key128bit = hash.slice(0, 16);
+  return key128bit.toString('hex');
+}
+
 // Module-level cache for channel IDs
 const channelIdCache: Record<string, string> = {};