Do a better job at faking simple challenge signatures.

chromeos/dbus/proto/attestation.proto

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
 package chromeos.attestation;
 
 // The message used by the attestation service for challenge response.
 message SignedData {
   // The data which was signed.
   optional bytes data = 1;
   // The signature of the data field.
   optional bytes signature = 2;
 }