diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 7cff831..107b6f5 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -14,6 +14,7 @@
 
 from __future__ import print_function
 
+import base64
 import collections
 import copy
 import errno
@@ -30,7 +31,6 @@
 import re
 import shlex
 import shutil
-import string
 import subprocess
 import sys
 import tempfile
@@ -190,6 +190,8 @@
     kwargs: Any additional args to be passed to subprocess.Popen(), such as env,
         stdin, etc. stdout and stderr will default to subprocess.PIPE and
         subprocess.STDOUT respectively unless caller specifies any of them.
+        universal_newlines will default to True, as most of the users in
+        releasetools expect string output.
 
   Returns:
     A subprocess.Popen object.
@@ -197,6 +199,8 @@
   if 'stdout' not in kwargs and 'stderr' not in kwargs:
     kwargs['stdout'] = subprocess.PIPE
     kwargs['stderr'] = subprocess.STDOUT
+  if 'universal_newlines' not in kwargs:
+    kwargs['universal_newlines'] = True
   # Don't log any if caller explicitly says so.
   if verbose != False:
     logger.info("  Running: \"%s\"", " ".join(args))
@@ -314,7 +318,7 @@
 
   def read_helper(fn):
     if isinstance(input_file, zipfile.ZipFile):
-      return input_file.read(fn)
+      return input_file.read(fn).decode()
     else:
       path = os.path.join(input_file, *fn.split("/"))
       try:
@@ -526,7 +530,7 @@
   # system. Other areas assume system is always at "/system" so point /system
   # at /.
   if system_root_image:
-    assert not d.has_key("/system") and d.has_key("/")
+    assert '/system' not in d and '/' in d
     d["/system"] = d["/"]
   return d
 
@@ -953,7 +957,7 @@
     # filename listed in system.map may contain an additional leading slash
     # (i.e. "//system/framework/am.jar"). Using lstrip to get consistent
     # results.
-    arcname = string.replace(entry, which, which.upper(), 1).lstrip('/')
+    arcname = entry.replace(which, which.upper(), 1).lstrip('/')
 
     # Special handling another case, where files not under /system
     # (e.g. "/sbin/charger") are packed under ROOT/ in a target_files.zip.
@@ -1223,7 +1227,7 @@
     if basename:
       installed_files.add(basename)
 
-  for line in tf_zip.read("META/apkcerts.txt").split("\n"):
+  for line in tf_zip.read('META/apkcerts.txt').decode().split('\n'):
     line = line.strip()
     if not line:
       continue
@@ -1433,6 +1437,8 @@
 
       if not first:
         print("key file %s still missing some passwords." % (self.pwfile,))
+        if sys.version_info[0] >= 3:
+          raw_input = input  # pylint: disable=redefined-builtin
         answer = raw_input("try to edit again? [y]> ").strip()
         if answer and answer[0] not in 'yY':
           raise RuntimeError("key passwords unavailable")
@@ -2185,7 +2191,7 @@
   This gives the same result as `openssl x509 -in <filename> -outform DER`.
 
   Returns:
-    The decoded certificate string.
+    The decoded certificate bytes.
   """
   cert_buffer = []
   save = False
@@ -2196,7 +2202,7 @@
       cert_buffer.append(line)
     if "--BEGIN CERTIFICATE--" in line:
       save = True
-  cert = "".join(cert_buffer).decode('base64')
+  cert = base64.b64decode("".join(cert_buffer))
   return cert
 
 
@@ -2338,7 +2344,7 @@
 
   logger.info("putting script in %s", sh_location)
 
-  output_sink(sh_location, sh)
+  output_sink(sh_location, sh.encode())
 
 
 class DynamicPartitionUpdate(object):
diff --git a/tools/releasetools/test_common.py b/tools/releasetools/test_common.py
index 11ac9f5..914e58e 100644
--- a/tools/releasetools/test_common.py
+++ b/tools/releasetools/test_common.py
@@ -579,7 +579,7 @@
   def test_ExtractPublicKey(self):
     cert = os.path.join(self.testdata_dir, 'testkey.x509.pem')
     pubkey = os.path.join(self.testdata_dir, 'testkey.pubkey.pem')
-    with open(pubkey, 'rb') as pubkey_fp:
+    with open(pubkey) as pubkey_fp:
       self.assertEqual(pubkey_fp.read(), common.ExtractPublicKey(cert))
 
   def test_ExtractPublicKey_invalidInput(self):
@@ -590,15 +590,16 @@
   def test_ExtractAvbPublicKey(self):
     privkey = os.path.join(self.testdata_dir, 'testkey.key')
     pubkey = os.path.join(self.testdata_dir, 'testkey.pubkey.pem')
-    with open(common.ExtractAvbPublicKey(privkey)) as privkey_fp, \
-        open(common.ExtractAvbPublicKey(pubkey)) as pubkey_fp:
+    with open(common.ExtractAvbPublicKey(privkey), 'rb') as privkey_fp, \
+        open(common.ExtractAvbPublicKey(pubkey), 'rb') as pubkey_fp:
       self.assertEqual(privkey_fp.read(), pubkey_fp.read())
 
   def test_ParseCertificate(self):
     cert = os.path.join(self.testdata_dir, 'testkey.x509.pem')
 
     cmd = ['openssl', 'x509', '-in', cert, '-outform', 'DER']
-    proc = common.Run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    proc = common.Run(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                      universal_newlines=False)
     expected, _ = proc.communicate()
     self.assertEqual(0, proc.returncode)
 
@@ -914,7 +915,7 @@
     target_files = common.MakeTempFile(prefix='target_files-', suffix='.zip')
     with zipfile.ZipFile(target_files, 'w') as target_files_zip:
       info_values = ''.join(
-          ['{}={}\n'.format(k, v) for k, v in sorted(info_dict.iteritems())])
+          ['{}={}\n'.format(k, v) for k, v in sorted(info_dict.items())])
       common.ZipWriteStr(target_files_zip, 'META/misc_info.txt', info_values)
 
       FSTAB_TEMPLATE = "/dev/block/system {} ext4 ro,barrier=1 defaults"
@@ -1085,7 +1086,7 @@
     loc = os.path.join(self._tempdir, prefix, name)
     if not os.path.exists(os.path.dirname(loc)):
       os.makedirs(os.path.dirname(loc))
-    with open(loc, "w+") as f:
+    with open(loc, "wb") as f:
       f.write(data)
 
   def test_full_recovery(self):
@@ -1110,7 +1111,7 @@
     validate_target_files.ValidateInstallRecoveryScript(self._tempdir,
                                                         self._info)
     # Validate 'recovery-from-boot' with bonus argument.
-    self._out_tmp_sink("etc/recovery-resource.dat", "bonus", "SYSTEM")
+    self._out_tmp_sink("etc/recovery-resource.dat", b"bonus", "SYSTEM")
     common.MakeRecoveryPatch(self._tempdir, self._out_tmp_sink,
                              recovery_image, boot_image, self._info)
     validate_target_files.ValidateInstallRecoveryScript(self._tempdir,
@@ -1118,25 +1119,30 @@
 
 
 class MockScriptWriter(object):
-  """A class that mocks edify_generator.EdifyGenerator.
-  """
+  """A class that mocks edify_generator.EdifyGenerator."""
+
   def __init__(self, enable_comments=False):
     self.lines = []
     self.enable_comments = enable_comments
+
   def Comment(self, comment):
     if self.enable_comments:
-      self.lines.append("# {}".format(comment))
+      self.lines.append('# {}'.format(comment))
+
   def AppendExtra(self, extra):
     self.lines.append(extra)
+
   def __str__(self):
-    return "\n".join(self.lines)
+    return '\n'.join(self.lines)
 
 
 class MockBlockDifference(object):
+
   def __init__(self, partition, tgt, src=None):
     self.partition = partition
     self.tgt = tgt
     self.src = src
+
   def WriteScript(self, script, _, progress=None,
                   write_verify_script=False):
     if progress:
@@ -1144,11 +1150,13 @@
     script.AppendExtra("patch({});".format(self.partition))
     if write_verify_script:
       self.WritePostInstallVerifyScript(script)
+
   def WritePostInstallVerifyScript(self, script):
     script.AppendExtra("verify({});".format(self.partition))
 
 
 class FakeSparseImage(object):
+
   def __init__(self, size):
     self.blocksize = 4096
     self.total_blocks = size // 4096
@@ -1156,12 +1164,13 @@
 
 
 class DynamicPartitionsDifferenceTest(test_utils.ReleaseToolsTestCase):
+
   @staticmethod
   def get_op_list(output_path):
     with zipfile.ZipFile(output_path) as output_zip:
-      with output_zip.open("dynamic_partitions_op_list") as op_list:
-        return [line.strip() for line in op_list.readlines()
-                if not line.startswith("#")]
+      with output_zip.open('dynamic_partitions_op_list') as op_list:
+        return [line.decode().strip() for line in op_list.readlines()
+                if not line.startswith(b'#')]
 
   def setUp(self):
     self.script = MockScriptWriter()
diff --git a/tools/releasetools/validate_target_files.py b/tools/releasetools/validate_target_files.py
index 37d5d27..5d99c99 100755
--- a/tools/releasetools/validate_target_files.py
+++ b/tools/releasetools/validate_target_files.py
@@ -44,7 +44,7 @@
   """Constructs and returns a File object. Rounds up its size if needed."""
 
   assert os.path.exists(unpacked_name)
-  with open(unpacked_name, 'r') as f:
+  with open(unpacked_name, 'rb') as f:
     file_data = f.read()
   file_size = len(file_data)
   if round_up: