Merge "Updated the description for APPLICATION_ID and APPLICATION_DATA"
diff --git a/security/keymint/aidl/android/hardware/security/keymint/Tag.aidl b/security/keymint/aidl/android/hardware/security/keymint/Tag.aidl
index b28ebcb..42dfad5 100644
--- a/security/keymint/aidl/android/hardware/security/keymint/Tag.aidl
+++ b/security/keymint/aidl/android/hardware/security/keymint/Tag.aidl
@@ -504,7 +504,9 @@
* that is necessary during all uses of the key. In particular, calls to exportKey() and
* getKeyCharacteristics() must provide the same value to the clientId parameter, and calls to
* begin() must provide this tag and the same associated data as part of the inParams set. If
- * the correct data is not provided, the method must return ErrorCode::INVALID_KEY_BLOB.
+ * the correct data is not provided, the method must return ErrorCode::INVALID_KEY_BLOB. Note
+ * that a key with a zero-length APPLICATION_ID cannot have its key characteristics retrieved
+ * using getKeyCharacteristics() due to a historical limitation of the API.
*
* The content of this tag must be bound to the key cryptographically, meaning it must not be
* possible for an adversary who has access to all of the secure world secrets but does not have
@@ -525,7 +527,9 @@
* that is necessary during all uses of the key. In particular, calls to begin() and
* exportKey() must provide the same value to the appData parameter, and calls to begin must
* provide this tag and the same associated data as part of the inParams set. If the correct
- * data is not provided, the method must return ErrorCode::INVALID_KEY_BLOB.
+ * data is not provided, the method must return ErrorCode::INVALID_KEY_BLOB. Note that a key
+ * with a zero-length APPLICATION_DATA cannot have its key characteristics retrieved using
+ * getKeyCharacteristics() due to a historical limitation of the API.
*
* The content of this tag must be bound to the key cryptographically, meaning it must not be
* possible for an adversary who has access to all of the secure world secrets but does not have