diff --git a/sdk-update/src/main/java/com/xuqm/sdk/update/UpdateSDK.kt b/sdk-update/src/main/java/com/xuqm/sdk/update/UpdateSDK.kt
index bc2f39d..d0310dd 100644
--- a/sdk-update/src/main/java/com/xuqm/sdk/update/UpdateSDK.kt
+++ b/sdk-update/src/main/java/com/xuqm/sdk/update/UpdateSDK.kt
@@ -106,15 +106,20 @@ object UpdateSDK {
      * 计算文件的 SHA-256 哈希值（小写十六进制）。
      */
     private fun computeFileHash(file: File): String {
-        val digest = MessageDigest.getInstance("SHA-256")
+        val md = MessageDigest.getInstance("SHA-256")
         file.inputStream().use { input ->
             val buffer = ByteArray(8192)
             var read: Int
             while (input.read(buffer).also { read = it } != -1) {
-                digest.update(buffer, 0, read)
+                md.update(buffer, 0, read)
             }
         }
-        return digest.joinToString("") { "%02x".format(it) }
+        val bytes = md.digest()
+        val sb = StringBuilder(bytes.size * 2)
+        for (b in bytes) {
+            sb.append(String.format("%02x", b.toInt() and 0xFF))
+        }
+        return sb.toString()
     }
 
     /**