fix: show real identity fingerprint (SHA-256 full format) on Android home screen

android/app/src/main/java/com/wzp/engine/WzpEngine.kt

@@ -159,6 +159,18 @@ class WzpEngine(private val callback: WzpCallback) {
     private external fun nativeWriteAudioDirect(handle: Long, buffer: java.nio.ByteBuffer, sampleCount: Int): Int
     private external fun nativeReadAudioDirect(handle: Long, buffer: java.nio.ByteBuffer, maxSamples: Int): Int
     private external fun nativeDestroy(handle: Long)
+
+    companion object {
+        init { System.loadLibrary("wzp_android") }
+
+        /** Get the identity fingerprint for a seed hex. No engine needed. */
+        @JvmStatic
+        private external fun nativeGetFingerprint(seedHex: String): String?
+
+        /** Compute the full identity fingerprint (xxxx:xxxx:...) from a seed hex string. */
+        @JvmStatic
+        fun getFingerprint(seedHex: String): String = nativeGetFingerprint(seedHex) ?: ""
+    }
     private external fun nativePingRelay(handle: Long, relay: String): String?
     private external fun nativeStartSignaling(handle: Long, relay: String, seed: String, token: String, alias: String): Int
     private external fun nativePlaceCall(handle: Long, targetFp: String): Int
@@ -208,11 +220,6 @@ class WzpEngine(private val callback: WzpCallback) {
         return nativeAnswerCall(nativeHandle, callId, mode)
     }
 
-    companion object {
-        init {
-            System.loadLibrary("wzp_android")
-        }
-    }
 }
 
 /** Integer constants matching the Rust [CallState] enum ordinals. */

android/app/src/main/java/com/wzp/ui/call/InCallScreen.kt

@@ -431,14 +431,16 @@ fun InCallScreen(
 
                 Spacer(modifier = Modifier.height(20.dp))
 
-                // Identity
+                // Identity — compute real fingerprint from seed
-                val fp = if (seedHex.length >= 16) seedHex.take(16) else ""
+                val fullFp = remember(seedHex) {
+                    if (seedHex.length >= 64) com.wzp.engine.WzpEngine.getFingerprint(seedHex) else ""
+                }
                 Row(verticalAlignment = Alignment.CenterVertically) {
-                    if (fp.isNotEmpty()) {
+                    if (fullFp.isNotEmpty()) {
-                        Identicon(fingerprint = seedHex, size = 28.dp)
+                        Identicon(fingerprint = fullFp, size = 28.dp)
                         Spacer(modifier = Modifier.width(8.dp))
                         CopyableFingerprint(
-                            fingerprint = fp.chunked(4).joinToString(":"),
+                            fingerprint = fullFp,
                             style = MaterialTheme.typography.bodySmall.copy(fontFamily = FontFamily.Monospace),
                             color = TextDim
                         )

crates/wzp-android/src/jni_bridge.rs

@@ -363,6 +363,31 @@ pub unsafe extern "system" fn Java_com_wzp_engine_WzpEngine_nativePingRelay<'a>(
         .unwrap_or(JObject::null().into_raw())
 }
 
+/// Get the identity fingerprint for a seed hex string.
+/// Returns the full fingerprint (xxxx:xxxx:...) or empty string on error.
+#[unsafe(no_mangle)]
+pub unsafe extern "system" fn Java_com_wzp_engine_WzpEngine_nativeGetFingerprint<'a>(
+    mut env: JNIEnv<'a>,
+    _class: JClass,
+    seed_hex_j: JString,
+) -> jstring {
+    let seed_hex: String = env.get_string(&seed_hex_j).map(|s| s.into()).unwrap_or_default();
+    let fp = if seed_hex.is_empty() {
+        String::new()
+    } else {
+        match wzp_crypto::Seed::from_hex(&seed_hex) {
+            Ok(seed) => {
+                let id = seed.derive_identity();
+                id.public_identity().fingerprint.to_string()
+            }
+            Err(_) => String::new(),
+        }
+    };
+    env.new_string(&fp)
+        .map(|s| s.into_raw())
+        .unwrap_or(JObject::null().into_raw())
+}
+
 // ── Direct calling JNI functions ──
 
 /// Start persistent signaling connection to relay for direct calls.