1 files changed, 10 insertions, 3 deletions
diff --git a/identity/java/android/security/identity/Util.java b/identity/java/android/security/identity/Util.java
index 6eefeb8f3f2a..e56bd5167906 100644
--- a/identity/java/android/security/identity/Util.java
+++ b/identity/java/android/security/identity/Util.java
@@ -16,6 +16,8 @@
 
 package android.security.identity;
 
+import android.annotation.NonNull;
+
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.security.InvalidKeyException;
@@ -28,7 +30,10 @@ import java.util.Collection;
 import javax.crypto.Mac;
 import javax.crypto.spec.SecretKeySpec;
 
-class Util {
+/**
+ * @hide
+ */
+public class Util {
     private static final String TAG = "Util";
 
     static int[] integerCollectionToArray(Collection<Integer> collection) {
@@ -91,8 +96,9 @@ class Util {
      *                     255.DigestSize, where DigestSize is the size of the underlying HMAC.
      * @return size pseudorandom bytes.
      */
-    static byte[] computeHkdf(
-            String macAlgorithm, final byte[] ikm, final byte[] salt, final byte[] info, int size) {
+    @NonNull public static byte[] computeHkdf(
+            @NonNull String macAlgorithm, @NonNull final byte[] ikm, @NonNull final byte[] salt,
+            @NonNull final byte[] info, int size) {
         Mac mac = null;
         try {
             mac = Mac.getInstance(macAlgorithm);
@@ -137,4 +143,5 @@ class Util {
         }
     }
 
+    private Util() {}
 }