diff --git a/payload_generator/generate_delta_main.cc b/payload_generator/generate_delta_main.cc
index d7d4f35..d93313f 100644
--- a/payload_generator/generate_delta_main.cc
+++ b/payload_generator/generate_delta_main.cc
@@ -29,6 +29,8 @@
 #include <brillo/flag_helper.h>
 #include <brillo/key_value_store.h>
 
+#include "update_engine/common/fake_boot_control.h"
+#include "update_engine/common/fake_hardware.h"
 #include "update_engine/common/prefs.h"
 #include "update_engine/common/terminator.h"
 #include "update_engine/common/utils.h"
@@ -179,43 +181,58 @@
 // TODO(deymo): This function is likely broken for deltas minor version 2 or
 // newer. Move this function to a new file and make the delta_performer
 // integration tests use this instead.
-void ApplyDelta(const string& in_file,
-                const string& old_kernel,
-                const string& old_rootfs,
-                const string& prefs_dir) {
+bool ApplyPayload(const string& payload_file,
+                  // Simply reuses the payload config used for payload
+                  // generation.
+                  const PayloadGenerationConfig& config) {
   LOG(INFO) << "Applying delta.";
-  LOG_IF(FATAL, old_rootfs.empty())
-      << "Must pass --old_image to apply delta.";
-  Prefs prefs;
+  FakeBootControl fake_boot_control;
+  FakeHardware fake_hardware;
+  MemoryPrefs prefs;
   InstallPlan install_plan;
-  LOG(INFO) << "Setting up preferences under: " << prefs_dir;
-  LOG_IF(ERROR, !prefs.Init(base::FilePath(prefs_dir)))
-      << "Failed to initialize preferences.";
-  // Get original checksums
-  LOG(INFO) << "Calculating original checksums";
-  ImageConfig old_image;
-  old_image.partitions.emplace_back(kLegacyPartitionNameRoot);
-  old_image.partitions.back().path = old_rootfs;
-  old_image.partitions.emplace_back(kLegacyPartitionNameKernel);
-  old_image.partitions.back().path = old_kernel;
-  CHECK(old_image.LoadImageSize());
-  for (const auto& old_part : old_image.partitions) {
-    PartitionInfo part_info;
-    CHECK(diff_utils::InitializePartitionInfo(old_part, &part_info));
+  install_plan.source_slot =
+      config.is_delta ? 0 : BootControlInterface::kInvalidSlot;
+  install_plan.target_slot = 1;
+  install_plan.payload_type =
+      config.is_delta ? InstallPayloadType::kDelta : InstallPayloadType::kFull;
+
+  for (size_t i = 0; i < config.target.partitions.size(); i++) {
     InstallPlan::Partition part;
-    part.name = old_part.name;
-    part.source_hash.assign(part_info.hash().begin(),
-                            part_info.hash().end());
-    part.source_path = old_part.path;
-    // Apply the delta in-place to the old_part.
-    part.target_path = old_part.path;
+    part.name = config.target.partitions[i].name;
+    part.target_path = config.target.partitions[i].path;
+    fake_boot_control.SetPartitionDevice(
+        part.name, install_plan.target_slot, part.target_path);
+
+    if (config.is_delta) {
+      TEST_AND_RETURN_FALSE(config.target.partitions.size() ==
+                            config.source.partitions.size());
+      PartitionInfo part_info;
+      TEST_AND_RETURN_FALSE(diff_utils::InitializePartitionInfo(
+          config.source.partitions[i], &part_info));
+      part.source_hash.assign(part_info.hash().begin(), part_info.hash().end());
+      part.source_path = config.source.partitions[i].path;
+
+      fake_boot_control.SetPartitionDevice(
+          part.name, install_plan.source_slot, part.source_path);
+    }
+
     install_plan.partitions.push_back(part);
+
+    LOG(INFO) << "Install partition:"
+              << " source: " << part.source_path
+              << " target: " << part.target_path;
+
   }
 
-  DeltaPerformer performer(
-      &prefs, nullptr, nullptr, nullptr, &install_plan, true);
+  DeltaPerformer performer(&prefs,
+                           &fake_boot_control,
+                           &fake_hardware,
+                           nullptr,
+                           &install_plan,
+                           true);  // is_interactive
+
   brillo::Blob buf(1024 * 1024);
-  int fd = open(in_file.c_str(), O_RDONLY, 0);
+  int fd = open(payload_file.c_str(), O_RDONLY, 0);
   CHECK_GE(fd, 0);
   ScopedFdCloser fd_closer(&fd);
   for (off_t offset = 0;; offset += buf.size()) {
@@ -223,11 +240,13 @@
     CHECK(utils::PReadAll(fd, buf.data(), buf.size(), offset, &bytes_read));
     if (bytes_read == 0)
       break;
-    CHECK_EQ(performer.Write(buf.data(), bytes_read), bytes_read);
+    TEST_AND_RETURN_FALSE(performer.Write(buf.data(), bytes_read));
   }
   CHECK_EQ(performer.Close(), 0);
   DeltaPerformer::ResetUpdateProgress(&prefs, false);
-  LOG(INFO) << "Done applying delta.";
+  LOG(INFO) << "Completed applying " << (config.is_delta ? "delta" : "full")
+            << " payload.";
+  return true;
 }
 
 int ExtractProperties(const string& payload_path, const string& props_file) {
@@ -289,8 +308,6 @@
   DEFINE_string(public_key, "", "Path to public key in .pem format");
   DEFINE_int32(public_key_version, -1,
                "DEPRECATED. Key-check version # of client");
-  DEFINE_string(prefs_dir, "/tmp/update_engine_prefs",
-                "Preferences directory, used with apply_delta");
   DEFINE_string(signature_size, "",
                 "Raw signature size used for hash calculation. "
                 "You may pass in multiple sizes by colon separating them. E.g. "
@@ -401,11 +418,6 @@
   if (!FLAGS_properties_file.empty()) {
     return ExtractProperties(FLAGS_in_file, FLAGS_properties_file) ? 0 : 1;
   }
-  if (!FLAGS_in_file.empty()) {
-    ApplyDelta(FLAGS_in_file, FLAGS_old_kernel, FLAGS_old_image,
-               FLAGS_prefs_dir);
-    return 0;
-  }
 
   // A payload generation was requested. Convert the flags to a
   // PayloadGenerationConfig.
@@ -488,6 +500,11 @@
     }
   }
 
+  if (!FLAGS_in_file.empty()) {
+    ApplyPayload(FLAGS_in_file, payload_config);
+    return 0;
+  }
+
   if (!FLAGS_new_postinstall_config_file.empty()) {
     LOG_IF(FATAL, FLAGS_major_version == kChromeOSMajorPayloadVersion)
         << "Postinstall config is only allowed in major version 2 or newer.";
@@ -563,11 +580,8 @@
     LOG(INFO) << "Using provided minor_version=" << FLAGS_minor_version;
   }
 
-  if (payload_config.is_delta) {
-    LOG(INFO) << "Generating delta update";
-  } else {
-    LOG(INFO) << "Generating full update";
-  }
+  LOG(INFO) << "Generating " << (payload_config.is_delta ? "delta" : "full")
+            << " update";
 
   // From this point, all the options have been parsed.
   if (!payload_config.Validate()) {
diff --git a/scripts/brillo_update_payload b/scripts/brillo_update_payload
index b139491..911d622 100755
--- a/scripts/brillo_update_payload
+++ b/scripts/brillo_update_payload
@@ -1,8 +1,20 @@
 #!/bin/bash
 
-# Copyright 2015 The Chromium OS Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
+#
+# Copyright (C) 2015 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
 
 # Script to generate a Brillo update for use by the update engine.
 #
@@ -12,14 +24,15 @@
 #  hash        generate a payload or metadata hash
 #  sign        generate a signed payload
 #  properties  generate a properties file from a payload
+#  verify      verify a payload by recreating a target image.
 #
 #  Generate command arguments:
 #  --payload             generated unsigned payload output file
 #  --source_image        if defined, generate a delta payload from the specified
 #                        image to the target_image
 #  --target_image        the target image that should be sent to clients
-#  --metadata_size_file  if defined, generate a file containing the size of the payload
-#                        metadata in bytes to the specified file
+#  --metadata_size_file  if defined, generate a file containing the size of the
+#                        payload metadata in bytes to the specified file
 #
 #  Hash command arguments:
 #  --unsigned_payload    the input unsigned payload to generate the hash from
@@ -50,6 +63,10 @@
 #  --payload                 the input signed or unsigned payload
 #  --properties_file         the output path where to write the properties, or
 #                            '-' for stdout.
+#  Verify command arguments:
+#  --payload             payload input file
+#  --source_image        verify payload to the specified source image.
+#  --target_image        the target image to verify upon.
 
 
 # Exit codes:
@@ -85,6 +102,7 @@
 for signing."
 HELP_SIGN="sign: Insert the signatures into the unsigned payload."
 HELP_PROPERTIES="properties: Extract payload properties to a file."
+HELP_VERIFY="verify: Verify a (signed) update payload."
 
 usage() {
   echo "Supported commands:"
@@ -93,6 +111,7 @@
   echo "${HELP_HASH}"
   echo "${HELP_SIGN}"
   echo "${HELP_PROPERTIES}"
+  echo "${HELP_VERIFY}"
   echo
   echo "Use: \"$0 <command> --help\" for more options."
 }
@@ -123,6 +142,11 @@
   properties)
     FLAGS_HELP="${HELP_PROPERTIES}"
     ;;
+
+  verify)
+    FLAGS_HELP="${HELP_VERIFY}"
+    ;;
+
   *)
     echo "Unrecognized command: \"${COMMAND}\"" >&2
     usage >&2
@@ -174,6 +198,15 @@
     "Path to output the extracted property files. If '-' is passed stdout will \
 be used."
 fi
+if [[ "${COMMAND}" == "verify" ]]; then
+  DEFINE_string payload "" \
+    "Path to the input payload file."
+  DEFINE_string target_image "" \
+    "Path to the target image to verify upon."
+  DEFINE_string source_image "" \
+    "Optional: Path to a source image. If specified, the delta update is \
+applied to this."
+fi
 
 DEFINE_string work_dir "${TMPDIR:-/tmp}" "Where to dump temporary files."
 
@@ -621,6 +654,87 @@
       -properties_file="${FLAGS_properties_file}"
 }
 
+validate_verify() {
+  [[ -n "${FLAGS_payload}" ]] ||
+    die "Error: you must specify an input filename with --payload FILENAME"
+
+  [[ -n "${FLAGS_target_image}" ]] ||
+    die "Error: you must specify a target image with --target_image FILENAME"
+}
+
+cmd_verify() {
+  local payload_type="delta"
+  if [[ -z "${FLAGS_source_image}" ]]; then
+    payload_type="full"
+  fi
+
+  echo "Extracting images for ${payload_type} update."
+
+  if [[ "${payload_type}" == "delta" ]]; then
+    extract_image "${FLAGS_source_image}" SRC_PARTITIONS
+  fi
+  extract_image "${FLAGS_target_image}" DST_PARTITIONS PARTITIONS_ORDER
+
+  declare -A TMP_PARTITIONS
+  for part in "${PARTITIONS_ORDER[@]}"; do
+    local tmp_part=$(create_tempfile "tmp_part.bin.XXXXXX")
+    echo "Creating temporary target partition ${tmp_part} for ${part}"
+    CLEANUP_FILES+=("${tmp_part}")
+    TMP_PARTITIONS[${part}]=${tmp_part}
+    local FILESIZE=$(stat -c%s "${DST_PARTITIONS[${part}]}")
+    echo "Truncating ${TMP_PARTITIONS[${part}]} to ${FILESIZE}"
+    truncate_file "${TMP_PARTITIONS[${part}]}" "${FILESIZE}"
+  done
+
+  echo "Verifying ${payload_type} update."
+  # Common payload args:
+  GENERATOR_ARGS=( -in_file="${FLAGS_payload}" )
+
+  local part old_partitions="" new_partitions="" partition_names=""
+  for part in "${PARTITIONS_ORDER[@]}"; do
+    if [[ -n "${partition_names}" ]]; then
+      partition_names+=":"
+      new_partitions+=":"
+      old_partitions+=":"
+    fi
+    partition_names+="${part}"
+    new_partitions+="${TMP_PARTITIONS[${part}]}"
+    old_partitions+="${SRC_PARTITIONS[${part}]:-}"
+  done
+
+  # Target image args:
+  GENERATOR_ARGS+=(
+    -partition_names="${partition_names}"
+    -new_partitions="${new_partitions}"
+  )
+
+  if [[ "${payload_type}" == "delta" ]]; then
+    # Source image args:
+    GENERATOR_ARGS+=(
+      -old_partitions="${old_partitions}"
+    )
+  fi
+
+  echo "Running delta_generator to verify ${payload_type} payload with args: \
+${GENERATOR_ARGS[@]}"
+  "${GENERATOR}" "${GENERATOR_ARGS[@]}"
+
+  if [[ $? -eq 0 ]]; then
+    echo "Done applying ${payload_type} update."
+    echo "Checking the newly generated partitions against the target partitions"
+    for part in "${PARTITIONS_ORDER[@]}"; do
+      cmp "${TMP_PARTITIONS[${part}]}" "${DST_PARTITIONS[${part}]}"
+      local not_str=""
+      if [[ $? -ne 0 ]]; then
+        not_str="in"
+      fi
+      echo "The new partition (${part}) is ${not_str}valid."
+    done
+  else
+    echo "Failed to apply ${payload_type} update."
+  fi
+}
+
 # Sanity check that the real generator exists:
 GENERATOR="$(which delta_generator || true)"
 [[ -x "${GENERATOR}" ]] || die "can't find delta_generator"
@@ -638,4 +752,7 @@
   properties) validate_properties
               cmd_properties
               ;;
+  verify) validate_verify
+          cmd_verify
+          ;;
 esac