diff --git a/tools/releasetools/check_ota_package_signature.py b/tools/releasetools/check_ota_package_signature.py
new file mode 100755
index 0000000..0da61b1
--- /dev/null
+++ b/tools/releasetools/check_ota_package_signature.py
@@ -0,0 +1,161 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2016 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.
+
+"""
+Verify a given OTA package with the specifed certificate.
+"""
+
+from __future__ import print_function
+
+import argparse
+import common
+import re
+import subprocess
+import sys
+
+from hashlib import sha1
+from hashlib import sha256
+
+
+def cert_uses_sha256(cert):
+  """Check if the cert uses SHA-256 hashing algorithm."""
+
+  cmd = ['openssl', 'x509', '-text', '-noout', '-in', cert]
+  p1 = common.Run(cmd, stdout=subprocess.PIPE)
+  cert_dump, _ = p1.communicate()
+
+  algorithm = re.search(r'Signature Algorithm: ([a-zA-Z0-9]+)', cert_dump)
+  assert algorithm, "Failed to identify the signature algorithm."
+
+  assert not algorithm.group(1).startswith('ecdsa'), (
+      'This script doesn\'t support verifying ECDSA signed package yet.')
+
+  return algorithm.group(1).startswith('sha256')
+
+
+def verify_package(cert, package):
+  """Verify the given package with the certificate.
+
+  (Comments from bootable/recovery/verifier.cpp:)
+
+  An archive with a whole-file signature will end in six bytes:
+
+    (2-byte signature start) $ff $ff (2-byte comment size)
+
+  (As far as the ZIP format is concerned, these are part of the
+  archive comment.) We start by reading this footer, this tells
+  us how far back from the end we have to start reading to find
+  the whole comment.
+  """
+
+  print('Package: %s' % (package,))
+  print('Certificate: %s' % (cert,))
+
+  # Read in the package.
+  with open(package) as package_file:
+    package_bytes = package_file.read()
+
+  length = len(package_bytes)
+  assert length >= 6, "Not big enough to contain footer."
+
+  footer = [ord(x) for x in package_bytes[-6:]]
+  assert footer[2] == 0xff and footer[3] == 0xff, "Footer is wrong."
+
+  signature_start_from_end = (footer[1] << 8) + footer[0]
+  assert signature_start_from_end > 6, "Signature start is in the footer."
+
+  signature_start = length - signature_start_from_end
+
+  # Determine how much of the file is covered by the signature. This is
+  # everything except the signature data and length, which includes all of the
+  # EOCD except for the comment length field (2 bytes) and the comment data.
+  comment_len = (footer[5] << 8) + footer[4]
+  signed_len = length - comment_len - 2
+
+  print('Package length: %d' % (length,))
+  print('Comment length: %d' % (comment_len,))
+  print('Signed data length: %d' % (signed_len,))
+  print('Signature start: %d' % (signature_start,))
+
+  use_sha256 = cert_uses_sha256(cert)
+  print('Use SHA-256: %s' % (use_sha256,))
+
+  if use_sha256:
+    h = sha256()
+  else:
+    h = sha1()
+  h.update(package_bytes[:signed_len])
+  package_digest = h.hexdigest().lower()
+
+  print('Digest: %s\n' % (package_digest,))
+
+  # Get the signature from the input package.
+  signature = package_bytes[signature_start:-6]
+  sig_file = common.MakeTempFile(prefix='sig-', suffix='')
+  with open(sig_file, 'wb') as f:
+    f.write(signature)
+
+  # Parse the signature and get the hash.
+  cmd = ['openssl', 'asn1parse', '-inform', 'DER', '-in', sig_file]
+  p1 = common.Run(cmd, stdout=subprocess.PIPE)
+  sig, _ = p1.communicate()
+  assert p1.returncode == 0, "Failed to parse the signature."
+
+  digest_line = sig.strip().split('\n')[-1]
+  digest_string = digest_line.split(':')[3]
+  digest_file = common.MakeTempFile(prefix='digest-', suffix='')
+  with open(digest_file, 'wb') as f:
+    f.write(digest_string.decode('hex'))
+
+  # Verify the digest by outputing the decrypted result in ASN.1 structure.
+  decrypted_file = common.MakeTempFile(prefix='decrypted-', suffix='')
+  cmd = ['openssl', 'rsautl', '-verify', '-certin', '-inkey', cert,
+         '-in', digest_file, '-out', decrypted_file]
+  p1 = common.Run(cmd, stdout=subprocess.PIPE)
+  p1.communicate()
+  assert p1.returncode == 0, "Failed to run openssl rsautl -verify."
+
+  # Parse the output ASN.1 structure.
+  cmd = ['openssl', 'asn1parse', '-inform', 'DER', '-in', decrypted_file]
+  p1 = common.Run(cmd, stdout=subprocess.PIPE)
+  decrypted_output, _ = p1.communicate()
+  assert p1.returncode == 0, "Failed to parse the output."
+
+  digest_line = decrypted_output.strip().split('\n')[-1]
+  digest_string = digest_line.split(':')[3].lower()
+
+  # Verify that the two digest strings match.
+  assert package_digest == digest_string, "Verification failed."
+
+  # Verified successfully upon reaching here.
+  print('VERIFIED\n')
+
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument('certificate', help='The certificate to be used.')
+  parser.add_argument('package', help='The OTA package to be verified.')
+  args = parser.parse_args()
+
+  verify_package(args.certificate, args.package)
+
+
+if __name__ == '__main__':
+  try:
+    main()
+  except AssertionError as err:
+    print('\n    ERROR: %s\n' % (err,))
+    sys.exit(1)