diff --git a/core/api/system-current.txt b/core/api/system-current.txt
index 49204e0c2098e..2e65bf3f15c55 100644
--- a/core/api/system-current.txt
+++ b/core/api/system-current.txt
@@ -5016,6 +5016,7 @@ package android.media.tv.tuner {
   public class Descrambler implements java.lang.AutoCloseable {
     method public int addPid(int, int, @Nullable android.media.tv.tuner.filter.Filter);
     method public void close();
+    method public static boolean isValidKeyToken(@NonNull byte[]);
     method public int removePid(int, int, @Nullable android.media.tv.tuner.filter.Filter);
     method public int setKeyToken(@NonNull byte[]);
     field public static final int PID_TYPE_MMTP = 2; // 0x2
@@ -5090,7 +5091,6 @@ package android.media.tv.tuner {
     field public static final int INVALID_FIRST_MACROBLOCK_IN_SLICE = -1; // 0xffffffff
     field public static final int INVALID_FRONTEND_ID = -1; // 0xffffffff
     field public static final int INVALID_FRONTEND_SETTING_FREQUENCY = -1; // 0xffffffff
-    field @NonNull public static final byte[] INVALID_KEYTOKEN;
     field public static final int INVALID_LTS_ID = -1; // 0xffffffff
     field public static final int INVALID_MMTP_RECORD_EVENT_MPT_SEQUENCE_NUM = -1; // 0xffffffff
     field public static final int INVALID_STREAM_ID = 65535; // 0xffff
@@ -5106,6 +5106,7 @@ package android.media.tv.tuner {
     field public static final int SCAN_TYPE_AUTO = 1; // 0x1
     field public static final int SCAN_TYPE_BLIND = 2; // 0x2
     field public static final int SCAN_TYPE_UNDEFINED = 0; // 0x0
+    field @NonNull public static final byte[] VOID_KEYTOKEN;
   }
 
   public static interface Tuner.OnResourceLostListener {
diff --git a/media/java/android/media/tv/tuner/Descrambler.java b/media/java/android/media/tv/tuner/Descrambler.java
index 2217eb3a1dc11..700e7beb06c67 100644
--- a/media/java/android/media/tv/tuner/Descrambler.java
+++ b/media/java/android/media/tv/tuner/Descrambler.java
@@ -110,14 +110,16 @@ public class Descrambler implements AutoCloseable {
     }
 
     /**
-     * Set a key token to link descrambler to a key slot
+     * Set a key token to link descrambler to a key slot. Use {@link isValidKeyToken(byte[])} to
+     * validate the key token format. Invalid key token would cause no-op and return
+     * {@link Tuner.RESULT_INVALID_ARGUMENT}.
      *
      * <p>A descrambler instance can have only one key slot to link, but a key slot can hold a few
-     * keys for different purposes.
+     * keys for different purposes. {@link Tuner.VOID_KEYTOKEN} is considered valid.
      *
-     * @param keyToken the token to be used to link the key slot. Use {@link Tuner.INVALID_KEYTOKEN}
+     * @param keyToken the token to be used to link the key slot. Use {@link Tuner.VOID_KEYTOKEN}
      *        to remove the current key from descrambler. If the current keyToken comes from a
-     *        MediaCas session, use {@link Tuner.INVALID_KEYTOKEN} to remove current key before
+     *        MediaCas session, use {@link Tuner.VOID_KEYTOKEN} to remove current key before
      *        closing the MediaCas session.
      * @return result status of the operation.
      */
@@ -133,6 +135,22 @@ public class Descrambler implements AutoCloseable {
         }
     }
 
+    /**
+     * Validate the key token format as the parameter of {@link setKeyToken(byte[])}.
+     *
+     * <p>The key token is expected to be less than 128 bits.
+     *
+     * @param keyToken the token to be validated.
+     * @return true if the given key token is a valid one.
+     */
+    public static boolean isValidKeyToken(@NonNull byte[] keyToken) {
+        if (keyToken.length == 0 || keyToken.length > 16) {
+            Log.d(TAG, "Invalid key token size: " + (keyToken.length * 8) + " bit.");
+            return false;
+        }
+        return true;
+    }
+
     /**
      * Release the descrambler instance.
      */
@@ -150,18 +168,4 @@ public class Descrambler implements AutoCloseable {
             }
         }
     }
-
-    private boolean isValidKeyToken(byte[] keyToken) {
-        if (keyToken.length == 0 || keyToken.length > 16) {
-            Log.d(TAG, "Invalid key token size: " + (keyToken.length * 8) + " bit.");
-            return false;
-        }
-        for (int i = 0; i < keyToken.length; i++) {
-            if (keyToken[i] < 0) {
-                Log.d(TAG, "Invalid key token.");
-                return false;
-            }
-        }
-        return true;
-    }
 }
diff --git a/media/java/android/media/tv/tuner/Tuner.java b/media/java/android/media/tv/tuner/Tuner.java
index da14ee1f32123..d094c2cd3c631 100644
--- a/media/java/android/media/tv/tuner/Tuner.java
+++ b/media/java/android/media/tv/tuner/Tuner.java
@@ -167,13 +167,13 @@ public class Tuner implements AutoCloseable  {
     public static final int INVALID_LNB_ID =
             android.hardware.tv.tuner.V1_1.Constants.Constant.INVALID_LNB_ID;
     /**
-     * Invalid key token. It is used to remove the current key from descrambler.
+     * A void key token. It is used to remove the current key from descrambler.
      *
      * <p>If the current keyToken comes from a MediaCas session, App is recommended to
      * to use this constant to remove current key before closing MediaCas session.
      */
     @NonNull
-    public static final byte[] INVALID_KEYTOKEN =
+    public static final byte[] VOID_KEYTOKEN =
             {android.hardware.tv.tuner.V1_1.Constants.Constant.INVALID_KEYTOKEN};
 
     /** @hide */