diff --git a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
index cade76d..87eaf96 100644
--- a/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
+++ b/biometrics/fingerprint/aidl/aidl_api/android.hardware.biometrics.fingerprint/current/android/hardware/biometrics/fingerprint/ISession.aidl
@@ -34,7 +34,7 @@
 package android.hardware.biometrics.fingerprint;
 @VintfStability
 interface ISession {
-  void generateChallenge(in int cookie, in int timeoutSec);
+  void generateChallenge(in int cookie);
   void revokeChallenge(in int cookie, in long challenge);
   android.hardware.biometrics.common.ICancellationSignal enroll(in int cookie, in android.hardware.keymaster.HardwareAuthToken hat);
   android.hardware.biometrics.common.ICancellationSignal authenticate(in int cookie, in long operationId);
diff --git a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
index ab7930d..ef2e6fc 100644
--- a/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
+++ b/biometrics/fingerprint/aidl/android/hardware/biometrics/fingerprint/ISession.aidl
@@ -61,7 +61,7 @@
      *      to allow addition of biometric enrollments.
      * To secure this path, the following path is taken:
      *   1) Upon user requesting fingerprint enroll, the framework requests
-     *      IFingerprint#generateChallenge
+     *      ISession#generateChallenge
      *   2) Framework sends the challenge to the credential subsystem, and upon credential
      *      confirmation, a HAT is created, containing the challenge in the "challenge" field.
      *   3) Framework sends the HAT to the HAL, e.g. ISession#enroll.
@@ -69,10 +69,9 @@
      *   5) Implementation now has confidence that the user entered their credential to allow
      *      biometric enrollment.
      *
-     * Note that the interface allows multiple in-flight challenges. For example, invoking
-     * generateChallenge(0, 0, timeoutSec, cb) twice does not invalidate the first challenge. The
-     * challenge is invalidated only when:
-     *   1) The provided timeout expires, or
+     * Note that this interface allows multiple in-flight challenges. Invoking generateChallenge
+     * twice does not invalidate the first challenge. The challenge is invalidated only when:
+     *   1) Its lifespan exceeds the HAL's internal challenge timeout
      *   2) IFingerprint#revokeChallenge is invoked
      *
      * For example, the following is a possible table of valid challenges:
@@ -86,9 +85,8 @@
      * ----------------------------------------------
      *
      * @param cookie A unique number identifying this operation
-     * @param timeoutSec Duration for which the challenge is valid for
      */
-    void generateChallenge(in int cookie, in int timeoutSec);
+    void generateChallenge(in int cookie);
 
     /**
      * revokeChallenge:
@@ -117,7 +115,7 @@
      *
      * Before capturing fingerprint data, the implementation must first verify the authenticity and
      * integrity of the provided HardwareAuthToken. In addition, it must check that the challenge
-     * within the provided HardwareAuthToken is valid. See IFingerprint#generateChallenge. If any of
+     * within the provided HardwareAuthToken is valid. See ISession#generateChallenge. If any of
      * the above checks fail, the framework must be notified via ISessionCallback#onError and the
      * HAL must notify the framework when it returns to the idle state. See
      * Error::UNABLE_TO_PROCESS.
diff --git a/biometrics/fingerprint/aidl/default/Session.cpp b/biometrics/fingerprint/aidl/default/Session.cpp
index f6a0314..9e6ac77 100644
--- a/biometrics/fingerprint/aidl/default/Session.cpp
+++ b/biometrics/fingerprint/aidl/default/Session.cpp
@@ -60,13 +60,13 @@
     return mCurrentState == SessionState::CLOSED;
 }
 
-ndk::ScopedAStatus Session::generateChallenge(int32_t cookie, int32_t timeoutSec) {
+ndk::ScopedAStatus Session::generateChallenge(int32_t cookie) {
     LOG(INFO) << "generateChallenge";
     scheduleStateOrCrash(SessionState::GENERATING_CHALLENGE);
 
-    mWorker->schedule(Callable::from([this, cookie, timeoutSec] {
+    mWorker->schedule(Callable::from([this, cookie] {
         enterStateOrCrash(cookie, SessionState::GENERATING_CHALLENGE);
-        mEngine->generateChallengeImpl(mCb.get(), timeoutSec);
+        mEngine->generateChallengeImpl(mCb.get());
         enterIdling(cookie);
     }));
 
diff --git a/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h b/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h
index 9343316..42e1aa5 100644
--- a/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h
+++ b/biometrics/fingerprint/aidl/default/include/FakeFingerprintEngine.h
@@ -22,7 +22,7 @@
 
 class FakeFingerprintEngine {
   public:
-    void generateChallengeImpl(ISessionCallback* cb, int32_t /*timeoutSec*/) {
+    void generateChallengeImpl(ISessionCallback* cb) {
         LOG(INFO) << "generateChallengeImpl";
         cb->onChallengeGenerated(0 /* challenge */);
     }
@@ -73,4 +73,4 @@
     }
 };
 
-}  // namespace aidl::android::hardware::biometrics::fingerprint
\ No newline at end of file
+}  // namespace aidl::android::hardware::biometrics::fingerprint
diff --git a/biometrics/fingerprint/aidl/default/include/Session.h b/biometrics/fingerprint/aidl/default/include/Session.h
index adda831..d2f0c19 100644
--- a/biometrics/fingerprint/aidl/default/include/Session.h
+++ b/biometrics/fingerprint/aidl/default/include/Session.h
@@ -32,7 +32,7 @@
     Session(int sensorId, int userId, std::shared_ptr<ISessionCallback> cb,
             FakeFingerprintEngine* engine, WorkerThread* worker);
 
-    ndk::ScopedAStatus generateChallenge(int32_t cookie, int32_t timeoutSec) override;
+    ndk::ScopedAStatus generateChallenge(int32_t cookie) override;
 
     ndk::ScopedAStatus revokeChallenge(int32_t cookie, int64_t challenge) override;