diff --git a/app/src/main/java/com/bitchat/android/util/BinaryEncodingUtils.kt b/app/src/main/java/com/bitchat/android/util/BinaryEncodingUtils.kt
index d2637403..06615332 100644
--- a/app/src/main/java/com/bitchat/android/util/BinaryEncodingUtils.kt
+++ b/app/src/main/java/com/bitchat/android/util/BinaryEncodingUtils.kt
@@ -27,7 +27,8 @@ fun String.dataFromHexString(): ByteArray? {
     if (hex.isEmpty()) {
         return ByteArray(0)
     }
-    if (hex.length % 2 != 0) {
+    // Radix parsing accepts signs and Unicode digits; encoded bytes require ASCII hex.
+    if (hex.length % 2 != 0 || hex.any { it !in '0'..'9' && it !in 'a'..'f' && it !in 'A'..'F' }) {
         return null
     }
 
diff --git a/app/src/test/java/com/bitchat/android/util/HexStringTest.kt b/app/src/test/java/com/bitchat/android/util/HexStringTest.kt
index b5b449bc..6472ede8 100644
--- a/app/src/test/java/com/bitchat/android/util/HexStringTest.kt
+++ b/app/src/test/java/com/bitchat/android/util/HexStringTest.kt
@@ -48,6 +48,13 @@ class HexStringTest {
         assertNull("0xgg".dataFromHexString())
     }
 
+    @Test
+    fun `rejects signed byte chunks and non-ascii digits`() {
+        for (invalid in listOf("0x-1", "0x+1", "-1", "+1", "00-1", "0X+100", "０１")) {
+            assertNull(invalid.dataFromHexString())
+        }
+    }
+
     @Test
     fun `round-trips with hexEncodedString`() {
         val original = byteArrayOf(0x00, 0x7f, 0xff.toByte())