diff --git a/api/crypto/framedecryptorinterface.h b/api/crypto/framedecryptorinterface.h
index a3ff19aa3c..1c49b511f7 100644
--- a/api/crypto/framedecryptorinterface.h
+++ b/api/crypto/framedecryptorinterface.h
@@ -25,8 +25,7 @@ namespace webrtc {
 // without it. You may assume that this interface will have the same lifetime
 // as the RTPReceiver it is attached to. It must only be attached to one
 // RTPReceiver.
-// Note:
-// This interface is not ready for production use.
+// Note: This interface is not ready for production use.
 class FrameDecryptorInterface : public rtc::RefCountInterface {
  public:
   ~FrameDecryptorInterface() override {}
@@ -35,16 +34,20 @@ class FrameDecryptorInterface : public rtc::RefCountInterface {
   // be allocated to the size returned from GetOutputSize. You may assume that
   // the frames are in order if SRTP is enabled. The stream is not provided here
   // and it is up to the implementor to transport this information to the
-  // receiver if they care about it.
-  // TODO(benwright) integrate error codes
-  virtual bool Decrypt(cricket::MediaType media_type,
-                       rtc::ArrayView<const uint8_t> encrypted_frame,
-                       rtc::ArrayView<uint8_t> frame) = 0;
+  // receiver if they care about it. You must set bytes_written to how many
+  // bytes you wrote to in the frame buffer. 0 must be returned if successful
+  // all other numbers can be selected by the implementer to represent error
+  // codes.
+  virtual int Decrypt(cricket::MediaType media_type,
+                      rtc::ArrayView<const uint8_t> encrypted_frame,
+                      rtc::ArrayView<uint8_t> frame,
+                      size_t* bytes_written) = 0;
 
   // Returns the total required length in bytes for the output of the
-  // decryption.
-  virtual size_t GetOutputSize(cricket::MediaType media_type,
-                               size_t encrypted_frame_size) = 0;
+  // decryption. This can be larger than the actual number of bytes you need but
+  // must never be smaller as it informs the size of the frame buffer.
+  virtual size_t GetMaxPlaintextByteSize(cricket::MediaType media_type,
+                                         size_t encrypted_frame_size) = 0;
 };
 
 }  // namespace webrtc
diff --git a/api/crypto/frameencryptorinterface.h b/api/crypto/frameencryptorinterface.h
index 369d6b8150..a99549c572 100644
--- a/api/crypto/frameencryptorinterface.h
+++ b/api/crypto/frameencryptorinterface.h
@@ -24,25 +24,29 @@ namespace webrtc {
 // addition to the standard SRTP mechanism and is not intended to be used
 // without it. Implementations of this interface will have the same lifetime as
 // the RTPSenders it is attached to.
-// This interface is not ready for production use.
+// Note: This interface is not ready for production use.
 class FrameEncryptorInterface : public rtc::RefCountInterface {
  public:
   ~FrameEncryptorInterface() override {}
 
   // Attempts to encrypt the provided frame. You may assume the encrypted_frame
-  // will match the size returned by GetOutputSize for a give frame. You may
-  // assume that the frames will arrive in order if SRTP is enabled. The ssrc
-  // will simply identify which stream the frame is travelling on.
-  // TODO(benwright) integrate error codes.
-  virtual bool Encrypt(cricket::MediaType media_type,
-                       uint32_t ssrc,
-                       rtc::ArrayView<const uint8_t> frame,
-                       rtc::ArrayView<uint8_t> encrypted_frame) = 0;
+  // will match the size returned by GetMaxCiphertextByteSize for a give frame.
+  // You may assume that the frames will arrive in order if SRTP is enabled.
+  // The ssrc will simply identify which stream the frame is travelling on. You
+  // must set bytes_written to the number of bytes you wrote in the
+  // encrypted_frame. 0 must be returned if successful all other numbers can be
+  // selected by the implementer to represent error codes.
+  virtual int Encrypt(cricket::MediaType media_type,
+                      uint32_t ssrc,
+                      rtc::ArrayView<const uint8_t> frame,
+                      rtc::ArrayView<uint8_t> encrypted_frame,
+                      size_t* bytes_written) = 0;
 
   // Returns the total required length in bytes for the output of the
-  // encryption.
-  virtual size_t GetOutputSize(cricket::MediaType media_type,
-                               size_t frame_size) = 0;
+  // encryption. This can be larger than the actual number of bytes you need but
+  // must never be smaller as it informs the size of the encrypted_frame buffer.
+  virtual size_t GetMaxCiphertextByteSize(cricket::MediaType media_type,
+                                          size_t frame_size) = 0;
 };
 
 }  // namespace webrtc