diff --git a/payload_generator/generate_delta_main.cc b/payload_generator/generate_delta_main.cc
index 5924f06..9c3655a 100644
--- a/payload_generator/generate_delta_main.cc
+++ b/payload_generator/generate_delta_main.cc
@@ -35,7 +35,6 @@
 #include "update_engine/payload_generator/delta_diff_utils.h"
 #include "update_engine/payload_generator/payload_generation_config.h"
 #include "update_engine/payload_generator/payload_signer.h"
-#include "update_engine/payload_verifier.h"
 #include "update_engine/prefs.h"
 #include "update_engine/terminator.h"
 #include "update_engine/update_metadata.pb.h"
@@ -184,7 +183,7 @@
       << "Must pass --in_file to verify signed payload.";
   LOG_IF(FATAL, public_key.empty())
       << "Must pass --public_key to verify signed payload.";
-  CHECK(PayloadVerifier::VerifySignedPayload(in_file, public_key));
+  CHECK(PayloadSigner::VerifySignedPayload(in_file, public_key));
   LOG(INFO) << "Done verifying signed payload.";
 }
 
diff --git a/payload_generator/payload_file.cc b/payload_generator/payload_file.cc
index 670027b..15dd35e 100644
--- a/payload_generator/payload_file.cc
+++ b/payload_generator/payload_file.cc
@@ -25,7 +25,6 @@
 #include "update_engine/omaha_hash_calculator.h"
 #include "update_engine/payload_constants.h"
 #include "update_engine/payload_generator/annotated_operation.h"
-#include "update_engine/payload_generator/delta_diff_generator.h"
 #include "update_engine/payload_generator/delta_diff_utils.h"
 #include "update_engine/payload_generator/payload_signer.h"
 
@@ -101,7 +100,7 @@
 bool PayloadFile::WritePayload(const string& payload_file,
                                const string& data_blobs_path,
                                const string& private_key_path,
-                               uint64_t* medatata_size_out) {
+                               uint64_t* metadata_size_out) {
   // Reorder the data blobs with the manifest_.
   string ordered_blobs_path;
   TEST_AND_RETURN_FALSE(utils::MakeTempFile(
@@ -167,13 +166,17 @@
     TEST_AND_RETURN_FALSE(
         PayloadSigner::SignatureBlobLength(vector<string>(1, private_key_path),
                                            &signature_blob_length));
-    AddSignatureOp(next_blob_offset, signature_blob_length, &manifest_);
+    PayloadSigner::AddSignatureOp(next_blob_offset, signature_blob_length,
+                                  &manifest_);
   }
 
   // Serialize protobuf
   string serialized_manifest;
   TEST_AND_RETURN_FALSE(manifest_.AppendToString(&serialized_manifest));
 
+  uint64_t metadata_size =
+      sizeof(kDeltaMagic) + 2 * sizeof(uint64_t) + serialized_manifest.size();
+
   LOG(INFO) << "Writing final delta file header...";
   DirectFileWriter writer;
   TEST_AND_RETURN_FALSE_ERRNO(writer.Open(payload_file.c_str(),
@@ -195,6 +198,7 @@
     // Write metadata signature size.
     uint32_t zero = htobe32(0);
     TEST_AND_RETURN_FALSE(writer.Write(&zero, sizeof(zero)));
+    metadata_size += sizeof(zero);
   }
 
   // Write protobuf
@@ -231,9 +235,8 @@
                                        signature_blob.size()));
   }
 
-  *medatata_size_out =
-      sizeof(kDeltaMagic) + 2 * sizeof(uint64_t) + serialized_manifest.size();
-  ReportPayloadUsage(*medatata_size_out);
+  ReportPayloadUsage(metadata_size);
+  *metadata_size_out = metadata_size;
   return true;
 }
 
@@ -317,24 +320,4 @@
           100.0, static_cast<intmax_t>(total_size), "", "<total>");
 }
 
-void AddSignatureOp(uint64_t signature_blob_offset,
-                    uint64_t signature_blob_length,
-                    DeltaArchiveManifest* manifest) {
-  LOG(INFO) << "Making room for signature in file";
-  manifest->set_signatures_offset(signature_blob_offset);
-  LOG(INFO) << "set? " << manifest->has_signatures_offset();
-  // Add a dummy op at the end to appease older clients
-  InstallOperation* dummy_op = manifest->add_kernel_install_operations();
-  dummy_op->set_type(InstallOperation::REPLACE);
-  dummy_op->set_data_offset(signature_blob_offset);
-  manifest->set_signatures_offset(signature_blob_offset);
-  dummy_op->set_data_length(signature_blob_length);
-  manifest->set_signatures_size(signature_blob_length);
-  Extent* dummy_extent = dummy_op->add_dst_extents();
-  // Tell the dummy op to write this data to a big sparse hole
-  dummy_extent->set_start_block(kSparseHole);
-  dummy_extent->set_num_blocks((signature_blob_length + kBlockSize - 1) /
-                               kBlockSize);
-}
-
 }  // namespace chromeos_update_engine
diff --git a/payload_generator/payload_file.h b/payload_generator/payload_file.h
index b586d73..51584d6 100644
--- a/payload_generator/payload_file.h
+++ b/payload_generator/payload_file.h
@@ -52,7 +52,7 @@
   bool WritePayload(const std::string& payload_file,
                     const std::string& data_blobs_path,
                     const std::string& private_key_path,
-                    uint64_t* medatata_size_out);
+                    uint64_t* metadata_size_out);
 
  private:
   FRIEND_TEST(PayloadFileTest, ReorderBlobsTest);
@@ -98,12 +98,6 @@
   std::vector<Partition> part_vec_;
 };
 
-// Adds a dummy operation that points to a signature blob located at the
-// specified offset/length.
-void AddSignatureOp(uint64_t signature_blob_offset,
-                    uint64_t signature_blob_length,
-                    DeltaArchiveManifest* manifest);
-
 }  // namespace chromeos_update_engine
 
 #endif  // UPDATE_ENGINE_PAYLOAD_GENERATOR_PAYLOAD_FILE_H_
diff --git a/payload_generator/payload_signer.cc b/payload_generator/payload_signer.cc
index 25ead8a..f5cd02e 100644
--- a/payload_generator/payload_signer.cc
+++ b/payload_generator/payload_signer.cc
@@ -24,7 +24,10 @@
 #include <brillo/data_encoding.h>
 #include <openssl/pem.h>
 
+#include "update_engine/delta_performer.h"
 #include "update_engine/omaha_hash_calculator.h"
+#include "update_engine/payload_constants.h"
+#include "update_engine/payload_generator/delta_diff_generator.h"
 #include "update_engine/payload_generator/payload_file.h"
 #include "update_engine/payload_verifier.h"
 #include "update_engine/subprocess.h"
@@ -83,9 +86,10 @@
   // Loads the payload.
   brillo::Blob payload;
   DeltaArchiveManifest manifest;
-  uint64_t metadata_size;
-  TEST_AND_RETURN_FALSE(PayloadVerifier::LoadPayload(
-      payload_path, &payload, &manifest, &metadata_size));
+  uint64_t metadata_size, major_version;
+  uint32_t metadata_signature_size;
+  TEST_AND_RETURN_FALSE(PayloadSigner::LoadPayload(payload_path, &payload,
+      &manifest, &major_version, &metadata_size, &metadata_signature_size));
 
   // Is there already a signature op in place?
   if (manifest.has_signatures_size()) {
@@ -103,9 +107,9 @@
     LOG(INFO) << "Matching signature sizes already present.";
   } else {
     // Updates the manifest to include the signature operation.
-    AddSignatureOp(payload.size() - metadata_size,
-                   signature_blob_size,
-                   &manifest);
+    PayloadSigner::AddSignatureOp(payload.size() - metadata_size,
+                                  signature_blob_size,
+                                  &manifest);
 
     // Updates the payload to include the new manifest.
     string serialized_manifest;
@@ -134,6 +138,99 @@
 }
 }  // namespace
 
+void PayloadSigner::AddSignatureOp(uint64_t signature_blob_offset,
+                                   uint64_t signature_blob_length,
+                                   DeltaArchiveManifest* manifest) {
+  LOG(INFO) << "Making room for signature in file";
+  manifest->set_signatures_offset(signature_blob_offset);
+  LOG(INFO) << "set? " << manifest->has_signatures_offset();
+  // Add a dummy op at the end to appease older clients
+  InstallOperation* dummy_op = manifest->add_kernel_install_operations();
+  dummy_op->set_type(InstallOperation::REPLACE);
+  dummy_op->set_data_offset(signature_blob_offset);
+  manifest->set_signatures_offset(signature_blob_offset);
+  dummy_op->set_data_length(signature_blob_length);
+  manifest->set_signatures_size(signature_blob_length);
+  Extent* dummy_extent = dummy_op->add_dst_extents();
+  // Tell the dummy op to write this data to a big sparse hole
+  dummy_extent->set_start_block(kSparseHole);
+  dummy_extent->set_num_blocks((signature_blob_length + kBlockSize - 1) /
+                               kBlockSize);
+}
+
+bool PayloadSigner::LoadPayload(const std::string& payload_path,
+                                brillo::Blob* out_payload,
+                                DeltaArchiveManifest* out_manifest,
+                                uint64_t* out_major_version,
+                                uint64_t* out_metadata_size,
+                                uint32_t* out_metadata_signature_size) {
+  brillo::Blob payload;
+  TEST_AND_RETURN_FALSE(utils::ReadFile(payload_path, &payload));
+  TEST_AND_RETURN_FALSE(payload.size() >=
+                        DeltaPerformer::kMaxPayloadHeaderSize);
+  const uint8_t* read_pointer = payload.data();
+  TEST_AND_RETURN_FALSE(
+      memcmp(read_pointer, kDeltaMagic, sizeof(kDeltaMagic)) == 0);
+  read_pointer += sizeof(kDeltaMagic);
+
+  uint64_t major_version;
+  memcpy(&major_version, read_pointer, sizeof(major_version));
+  read_pointer += sizeof(major_version);
+  major_version = be64toh(major_version);
+  TEST_AND_RETURN_FALSE(major_version == kChromeOSMajorPayloadVersion ||
+                        major_version == kBrilloMajorPayloadVersion);
+  if (out_major_version)
+    *out_major_version = major_version;
+
+  uint64_t manifest_size = 0;
+  memcpy(&manifest_size, read_pointer, sizeof(manifest_size));
+  read_pointer += sizeof(manifest_size);
+  manifest_size = be64toh(manifest_size);
+
+  uint32_t metadata_signature_size = 0;
+  if (major_version == kBrilloMajorPayloadVersion) {
+    memcpy(&metadata_signature_size, read_pointer,
+           sizeof(metadata_signature_size));
+    read_pointer += sizeof(metadata_signature_size);
+    metadata_signature_size = be32toh(metadata_signature_size);
+  }
+  if (out_metadata_signature_size)
+    *out_metadata_signature_size = metadata_signature_size;
+
+  *out_metadata_size = read_pointer - payload.data() + manifest_size;
+  TEST_AND_RETURN_FALSE(payload.size() >= *out_metadata_size);
+  if (out_manifest)
+    TEST_AND_RETURN_FALSE(
+        out_manifest->ParseFromArray(read_pointer, manifest_size));
+  *out_payload = std::move(payload);
+  return true;
+}
+
+bool PayloadSigner::VerifySignedPayload(const string& payload_path,
+                                        const string& public_key_path) {
+  brillo::Blob payload;
+  DeltaArchiveManifest manifest;
+  uint64_t metadata_size, major_version;
+  uint32_t metadata_signature_size;
+  TEST_AND_RETURN_FALSE(LoadPayload(payload_path, &payload, &manifest,
+      &major_version, &metadata_size, &metadata_signature_size));
+  TEST_AND_RETURN_FALSE(manifest.has_signatures_offset() &&
+                        manifest.has_signatures_size());
+  CHECK_EQ(payload.size(),
+           metadata_size + manifest.signatures_offset() +
+           manifest.signatures_size());
+  brillo::Blob signature_blob(
+      payload.begin() + metadata_size + manifest.signatures_offset(),
+      payload.end());
+  brillo::Blob hash;
+  TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfBytes(
+      payload.data(), metadata_size + manifest.signatures_offset(), &hash));
+  TEST_AND_RETURN_FALSE(PayloadVerifier::PadRSA2048SHA256Hash(&hash));
+  TEST_AND_RETURN_FALSE(PayloadVerifier::VerifySignature(
+      signature_blob, public_key_path, hash));
+  return true;
+}
+
 bool PayloadSigner::SignHash(const brillo::Blob& hash,
                              const string& private_key_path,
                              brillo::Blob* out_signature) {
diff --git a/payload_generator/payload_signer.h b/payload_generator/payload_signer.h
index 11116a3..d702ccc 100644
--- a/payload_generator/payload_signer.h
+++ b/payload_generator/payload_signer.h
@@ -32,6 +32,31 @@
 
 class PayloadSigner {
  public:
+  // Reads the payload from the given |payload_path| into the |out_payload|
+  // vector. It also parses the manifest protobuf in the payload and returns it
+  // in |out_manifest| if not null, along with the major version of the payload
+  // in |out_major_version| if not null, the size of the entire metadata in
+  // |out_metadata_size| and the size of metadata signature in
+  // |out_metadata_signature_size| if not null.
+  static bool LoadPayload(const std::string& payload_path,
+                          brillo::Blob* out_payload,
+                          DeltaArchiveManifest* out_manifest,
+                          uint64_t* out_major_version,
+                          uint64_t* out_metadata_size,
+                          uint32_t* out_metadata_signature_size);
+
+  // Returns true if the payload in |payload_path| is signed and its hash can be
+  // verified using the public key in |public_key_path| with the signature
+  // of a given version in the signature blob. Returns false otherwise.
+  static bool VerifySignedPayload(const std::string& payload_path,
+                                  const std::string& public_key_path);
+
+  // Adds a dummy operation that points to a signature blob located at the
+  // specified offset/length.
+  static void AddSignatureOp(uint64_t signature_blob_offset,
+                             uint64_t signature_blob_length,
+                             DeltaArchiveManifest* manifest);
+
   // Given a raw |hash| and a private key in |private_key_path| calculates the
   // raw signature in |out_signature|. Returns true on success, false otherwise.
   static bool SignHash(const brillo::Blob& hash,
diff --git a/payload_generator/payload_signer_unittest.cc b/payload_generator/payload_signer_unittest.cc
index 9ef6614..7763411 100644
--- a/payload_generator/payload_signer_unittest.cc
+++ b/payload_generator/payload_signer_unittest.cc
@@ -22,6 +22,7 @@
 #include <base/logging.h>
 #include <gtest/gtest.h>
 
+#include "update_engine/payload_generator/payload_file.h"
 #include "update_engine/payload_verifier.h"
 #include "update_engine/update_metadata.pb.h"
 #include "update_engine/utils.h"
@@ -119,9 +120,40 @@
     PayloadVerifier::PadRSA2048SHA256Hash(&padded_hash_data_);
   }
 
+  void DoWriteAndLoadPayloadTest(const PayloadGenerationConfig& config) {
+    PayloadFile payload;
+    payload.Init(config);
+    string payload_path;
+    EXPECT_TRUE(utils::MakeTempFile("payload.XXXXXX", &payload_path, nullptr));
+    ScopedPathUnlinker payload_path_unlinker(payload_path);
+    uint64_t metadata_size;
+    EXPECT_TRUE(
+        payload.WritePayload(payload_path, "/dev/null", "", &metadata_size));
+    brillo::Blob payload_blob;
+    DeltaArchiveManifest manifest;
+    uint64_t load_metadata_size, load_major_version;
+    EXPECT_TRUE(PayloadSigner::LoadPayload(payload_path, &payload_blob,
+        &manifest, &load_major_version, &load_metadata_size, nullptr));
+    EXPECT_EQ(utils::FileSize(payload_path), payload_blob.size());
+    EXPECT_EQ(config.major_version, load_major_version);
+    EXPECT_EQ(metadata_size, load_metadata_size);
+  }
+
   brillo::Blob padded_hash_data_{std::begin(kDataHash), std::end(kDataHash)};
 };
 
+TEST_F(PayloadSignerTest, LoadPayloadV1Test) {
+  PayloadGenerationConfig config;
+  config.major_version = kChromeOSMajorPayloadVersion;
+  DoWriteAndLoadPayloadTest(config);
+}
+
+TEST_F(PayloadSignerTest, LoadPayloadV2Test) {
+  PayloadGenerationConfig config;
+  config.major_version = kBrilloMajorPayloadVersion;
+  DoWriteAndLoadPayloadTest(config);
+}
+
 TEST_F(PayloadSignerTest, SignSimpleTextTest) {
   brillo::Blob signature_blob;
   SignSampleData(&signature_blob, {kUnittestPrivateKeyPath});