diff --git a/rsa/_compat.py b/rsa/_compat.py
index 39a967b..7533c36 100644
--- a/rsa/_compat.py
+++ b/rsa/_compat.py
@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Python compatibility wrappers.'''
+"""Python compatibility wrappers."""
 
 
 from __future__ import absolute_import
@@ -108,11 +108,6 @@
     Use it as a replacement for ``chr`` where you are expecting a byte
     because this will work on all current versions of Python::
 
-        >>> byte(0)
-        '\x00'
-        >>> byte(255)
-        '\xff'
-
     :param num:
         An unsigned integer between 0 and 255 (both inclusive).
     :returns:
diff --git a/rsa/bigfile.py b/rsa/bigfile.py
index 26063f1..ed3fdb9 100644
--- a/rsa/bigfile.py
+++ b/rsa/bigfile.py
@@ -13,7 +13,7 @@
 #  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.
-'''Large file support
+"""Large file support
 
     - break a file into smaller blocks, and encrypt them, and store the
       encrypted blocks in another file.
@@ -36,19 +36,19 @@
 This file format is called the VARBLOCK format, in line with the varint format
 used to denote the block sizes.
 
-'''
+"""
 
 from rsa import key, common, pkcs1, varblock
 from rsa._compat import byte
 
 def encrypt_bigfile(infile, outfile, pub_key):
-    '''Encrypts a file, writing it to 'outfile' in VARBLOCK format.
+    """Encrypts a file, writing it to 'outfile' in VARBLOCK format.
     
     :param infile: file-like object to read the cleartext from
     :param outfile: file-like object to write the crypto in VARBLOCK format to
     :param pub_key: :py:class:`rsa.PublicKey` to encrypt with
 
-    '''
+    """
 
     if not isinstance(pub_key, key.PublicKey):
         raise TypeError('Public key required, but got %r' % pub_key)
@@ -67,13 +67,13 @@
         outfile.write(crypto)
 
 def decrypt_bigfile(infile, outfile, priv_key):
-    '''Decrypts an encrypted VARBLOCK file, writing it to 'outfile'
+    """Decrypts an encrypted VARBLOCK file, writing it to 'outfile'
     
     :param infile: file-like object to read the crypto in VARBLOCK format from
     :param outfile: file-like object to write the cleartext to
     :param priv_key: :py:class:`rsa.PrivateKey` to decrypt with
 
-    '''
+    """
 
     if not isinstance(priv_key, key.PrivateKey):
         raise TypeError('Private key required, but got %r' % priv_key)
diff --git a/rsa/cli.py b/rsa/cli.py
index 012c77d..382a915 100644
--- a/rsa/cli.py
+++ b/rsa/cli.py
@@ -14,10 +14,12 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Commandline scripts.
+"""Commandline scripts.
 
 These scripts are called by the executables defined in setup.py.
-'''
+"""
+
+from __future__ import with_statement
 
 import abc
 import sys
@@ -30,7 +32,7 @@
 HASH_METHODS = sorted(rsa.pkcs1.HASH_METHODS.keys())
 
 def keygen():
-    '''Key generator.'''
+    """Key generator."""
 
     # Parse the CLI options
     parser = OptionParser(usage='usage: %prog [options] keysize',
@@ -86,7 +88,7 @@
 
 
 class CryptoOperation(object):
-    '''CLI callable that operates with input, output, and a key.'''
+    """CLI callable that operates with input, output, and a key."""
 
     __metaclass__ = abc.ABCMeta
 
@@ -112,15 +114,15 @@
 
     @abc.abstractmethod
     def perform_operation(self, indata, key, cli_args=None):
-        '''Performs the program's operation.
+        """Performs the program's operation.
 
         Implement in a subclass.
 
         :returns: the data to write to the output.
-        '''
+        """
 
     def __call__(self):
-        '''Runs the program.'''
+        """Runs the program."""
 
         (cli, cli_args) = self.parse_cli()
 
@@ -135,10 +137,10 @@
             self.write_outfile(outdata, cli.output)
 
     def parse_cli(self):
-        '''Parse the CLI options
+        """Parse the CLI options
         
         :returns: (cli_opts, cli_args)
-        '''
+        """
 
         parser = OptionParser(usage=self.usage, description=self.description)
         
@@ -160,7 +162,7 @@
         return (cli, cli_args)
 
     def read_key(self, filename, keyform):
-        '''Reads a public or private key.'''
+        """Reads a public or private key."""
 
         print >>sys.stderr, 'Reading %s key from %s' % (self.keyname, filename)
         with open(filename) as keyfile:
@@ -169,7 +171,7 @@
         return self.key_class.load_pkcs1(keydata, keyform)
     
     def read_infile(self, inname):
-        '''Read the input file'''
+        """Read the input file"""
 
         if inname:
             print >>sys.stderr, 'Reading input from %s' % inname
@@ -180,7 +182,7 @@
         return sys.stdin.read()
 
     def write_outfile(self, outdata, outname):
-        '''Write the output file'''
+        """Write the output file"""
 
         if outname:
             print >>sys.stderr, 'Writing output to %s' % outname
@@ -191,7 +193,7 @@
             sys.stdout.write(outdata)
 
 class EncryptOperation(CryptoOperation):
-    '''Encrypts a file.'''
+    """Encrypts a file."""
 
     keyname = 'public'
     description = ('Encrypts a file. The file must be shorter than the key '
@@ -203,12 +205,12 @@
 
 
     def perform_operation(self, indata, pub_key, cli_args=None):
-        '''Encrypts files.'''
+        """Encrypts files."""
 
         return rsa.encrypt(indata, pub_key)
 
 class DecryptOperation(CryptoOperation):
-    '''Decrypts a file.'''
+    """Decrypts a file."""
 
     keyname = 'private'
     description = ('Decrypts a file. The original file must be shorter than '
@@ -220,12 +222,12 @@
     key_class = rsa.PrivateKey
 
     def perform_operation(self, indata, priv_key, cli_args=None):
-        '''Decrypts files.'''
+        """Decrypts files."""
 
         return rsa.decrypt(indata, priv_key)
 
 class SignOperation(CryptoOperation):
-    '''Signs a file.'''
+    """Signs a file."""
 
     keyname = 'private'
     usage = 'usage: %%prog [options] private_key hash_method'
@@ -241,7 +243,7 @@
             'to stdout if this option is not present.')
 
     def perform_operation(self, indata, priv_key, cli_args):
-        '''Decrypts files.'''
+        """Decrypts files."""
 
         hash_method = cli_args[1]
         if hash_method not in HASH_METHODS:
@@ -251,7 +253,7 @@
         return rsa.sign(indata, priv_key, hash_method)
 
 class VerifyOperation(CryptoOperation):
-    '''Verify a signature.'''
+    """Verify a signature."""
 
     keyname = 'public'
     usage = 'usage: %%prog [options] private_key signature_file'
@@ -265,7 +267,7 @@
     has_output = False
 
     def perform_operation(self, indata, pub_key, cli_args):
-        '''Decrypts files.'''
+        """Decrypts files."""
 
         signature_file = cli_args[1]
         
@@ -281,7 +283,7 @@
 
 
 class BigfileOperation(CryptoOperation):
-    '''CryptoOperation that doesn't read the entire file into memory.'''
+    """CryptoOperation that doesn't read the entire file into memory."""
 
     def __init__(self):
         CryptoOperation.__init__(self)
@@ -289,13 +291,13 @@
         self.file_objects = []
 
     def __del__(self):
-        '''Closes any open file handles.'''
+        """Closes any open file handles."""
 
         for fobj in self.file_objects:
             fobj.close()
 
     def __call__(self):
-        '''Runs the program.'''
+        """Runs the program."""
 
         (cli, cli_args) = self.parse_cli()
 
@@ -310,7 +312,7 @@
         self.perform_operation(infile, outfile, key, cli_args)
 
     def get_infile(self, inname):
-        '''Returns the input file object'''
+        """Returns the input file object"""
 
         if inname:
             print >>sys.stderr, 'Reading input from %s' % inname
@@ -323,7 +325,7 @@
         return fobj
 
     def get_outfile(self, outname):
-        '''Returns the output file object'''
+        """Returns the output file object"""
 
         if outname:
             print >>sys.stderr, 'Will write output to %s' % outname
@@ -336,7 +338,7 @@
         return fobj
 
 class EncryptBigfileOperation(BigfileOperation):
-    '''Encrypts a file to VARBLOCK format.'''
+    """Encrypts a file to VARBLOCK format."""
 
     keyname = 'public'
     description = ('Encrypts a file to an encrypted VARBLOCK file. The file '
@@ -347,12 +349,12 @@
     operation_progressive = 'encrypting'
 
     def perform_operation(self, infile, outfile, pub_key, cli_args=None):
-        '''Encrypts files to VARBLOCK.'''
+        """Encrypts files to VARBLOCK."""
 
         return rsa.bigfile.encrypt_bigfile(infile, outfile, pub_key)
 
 class DecryptBigfileOperation(BigfileOperation):
-    '''Decrypts a file in VARBLOCK format.'''
+    """Decrypts a file in VARBLOCK format."""
 
     keyname = 'private'
     description = ('Decrypts an encrypted VARBLOCK file that was encrypted '
@@ -363,7 +365,7 @@
     key_class = rsa.PrivateKey
 
     def perform_operation(self, infile, outfile, priv_key, cli_args=None):
-        '''Decrypts a VARBLOCK file.'''
+        """Decrypts a VARBLOCK file."""
 
         return rsa.bigfile.decrypt_bigfile(infile, outfile, priv_key)
 
diff --git a/rsa/common.py b/rsa/common.py
index 11e52ec..5730ac3 100644
--- a/rsa/common.py
+++ b/rsa/common.py
@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Common functionality shared by several modules.'''
+"""Common functionality shared by several modules."""
 
 
 def bit_size(num):
@@ -61,29 +61,14 @@
 
 
 def _bit_size(number):
-    '''Returns the number of bits required to hold a specific long number.
-
-    >>> bit_size(1023)
-    10
-    >>> bit_size(1024)
-    11
-    >>> bit_size(1025)
-    11
-
-    >>> bit_size(1 << 1024)
-    1025
-    >>> bit_size((1 << 1024) + 1)
-    1025
-    >>> bit_size((1 << 1024) - 1)
-    1024
-
-    '''
-
+    """
+    Returns the number of bits required to hold a specific long number.
+    """
     if number < 0:
         raise ValueError('Only nonnegative numbers possible: %s' % number)
 
     if number == 0:
-        return 1
+        return 0
     
     # This works, even with very large numbers. When using math.log(number, 2),
     # you'll get rounding errors and it'll fail.
@@ -99,15 +84,9 @@
     """Returns the number of bytes required to hold a specific long number.
     
     The number of bytes is rounded up.
-
-    >>> byte_size(1 << 1023)
-    128
-    >>> byte_size((1 << 1024) - 1)
-    128
-    >>> byte_size(1 << 1024)
-    129
     """
-
+    if number == 0:
+        return 0
     # Does not perform floating-point division and uses built-in divmod
     # operator.
     quanta, mod = divmod(bit_size(number), 8)
@@ -140,13 +119,13 @@
     return (a, lx, ly)                 #Return only positive values
 
 def inverse(x, n):
-    '''Returns x^-1 (mod n)
+    """Returns x^-1 (mod n)
     
     >>> inverse(7, 4)
     3
     >>> (inverse(143, 4) * 143) % 4
     1
-    '''
+    """
 
     (divider, inv, _) = extended_gcd(x, n)
 
@@ -157,7 +136,7 @@
 
 
 def crt(a_values, modulo_values):
-    '''Chinese Remainder Theorem.
+    """Chinese Remainder Theorem.
 
     Calculates x such that x = a[i] (mod m[i]) for each i.
 
@@ -174,7 +153,7 @@
 
     >>> crt([2, 3, 0], [7, 11, 15])
     135
-    '''
+    """
 
     m = 1
     x = 0 
diff --git a/rsa/core.py b/rsa/core.py
index fbc108a..27d829e 100644
--- a/rsa/core.py
+++ b/rsa/core.py
@@ -13,11 +13,11 @@
 #  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.
-'''Core mathematical operations.
+"""Core mathematical operations.
 
 This is the actual core RSA implementation, which is only defined
 mathematically on integers.
-'''
+"""
 
 
 from rsa._compat import is_integer
diff --git a/rsa/key.py b/rsa/key.py
index facde8e..dc4465d 100644
--- a/rsa/key.py
+++ b/rsa/key.py
@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''RSA key generation code.
+"""RSA key generation code.
 
 Create new keys with the newkeys() function. It will give you a PublicKey and a
 PrivateKey object.
@@ -23,7 +23,7 @@
 late as possible, such that other functionality will remain working in absence
 of pyasn1.
 
-'''
+"""
 
 import logging
 from rsa._compat import b
@@ -35,11 +35,11 @@
 log = logging.getLogger(__name__)
 
 class AbstractKey(object):
-    '''Abstract superclass for private and public keys.'''
+    """Abstract superclass for private and public keys."""
 
     @classmethod
     def load_pkcs1(cls, keyfile, format='PEM'):
-        r'''Loads a key in PKCS#1 DER or PEM format.
+        r"""Loads a key in PKCS#1 DER or PEM format.
 
         :param keyfile: contents of a DER- or PEM-encoded file that contains
             the public key.
@@ -47,7 +47,7 @@
 
         :return: a PublicKey object
 
-        '''
+        """
 
         methods = {
             'PEM': cls._load_pkcs1_pem,
@@ -63,12 +63,12 @@
         return method(keyfile)
 
     def save_pkcs1(self, format='PEM'):
-        '''Saves the public key in PKCS#1 DER or PEM format.
+        """Saves the public key in PKCS#1 DER or PEM format.
 
         :param format: the format to save; 'PEM' or 'DER'
         :returns: the DER- or PEM-encoded public key.
 
-        '''
+        """
 
         methods = {
             'PEM': self._save_pkcs1_pem,
@@ -84,7 +84,7 @@
         return method()
 
 class PublicKey(AbstractKey):
-    '''Represents a public RSA key.
+    """Represents a public RSA key.
 
     This key is also known as the 'encryption key'. It contains the 'n' and 'e'
     values.
@@ -105,7 +105,7 @@
     >>> key['e']
     3
 
-    '''
+    """
 
     __slots__ = ('n', 'e')
 
@@ -133,7 +133,7 @@
 
     @classmethod
     def _load_pkcs1_der(cls, keyfile):
-        r'''Loads a key in PKCS#1 DER format.
+        r"""Loads a key in PKCS#1 DER format.
 
         @param keyfile: contents of a DER-encoded file that contains the public
             key.
@@ -150,7 +150,7 @@
         >>> PublicKey._load_pkcs1_der(der)
         PublicKey(2367317549, 65537)
 
-        '''
+        """
 
         from pyasn1.codec.der import decoder
         (priv, _) = decoder.decode(keyfile)
@@ -165,10 +165,10 @@
         return cls(*as_ints)
 
     def _save_pkcs1_der(self):
-        '''Saves the public key in PKCS#1 DER format.
+        """Saves the public key in PKCS#1 DER format.
 
         @returns: the DER-encoded public key.
-        '''
+        """
 
         from pyasn1.type import univ, namedtype
         from pyasn1.codec.der import encoder
@@ -188,7 +188,7 @@
 
     @classmethod
     def _load_pkcs1_pem(cls, keyfile):
-        '''Loads a PKCS#1 PEM-encoded public key file.
+        """Loads a PKCS#1 PEM-encoded public key file.
 
         The contents of the file before the "-----BEGIN RSA PUBLIC KEY-----" and
         after the "-----END RSA PUBLIC KEY-----" lines is ignored.
@@ -196,22 +196,22 @@
         @param keyfile: contents of a PEM-encoded file that contains the public
             key.
         @return: a PublicKey object
-        '''
+        """
 
         der = rsa.pem.load_pem(keyfile, 'RSA PUBLIC KEY')
         return cls._load_pkcs1_der(der)
 
     def _save_pkcs1_pem(self):
-        '''Saves a PKCS#1 PEM-encoded public key file.
+        """Saves a PKCS#1 PEM-encoded public key file.
 
         @return: contents of a PEM-encoded file that contains the public key.
-        '''
+        """
 
         der = self._save_pkcs1_der()
         return rsa.pem.save_pem(der, 'RSA PUBLIC KEY')
 
 class PrivateKey(AbstractKey):
-    '''Represents a private RSA key.
+    """Represents a private RSA key.
 
     This key is also known as the 'decryption key'. It contains the 'n', 'e',
     'd', 'p', 'q' and other values.
@@ -242,7 +242,7 @@
     >>> pk.coef
     8
 
-    '''
+    """
 
     __slots__ = ('n', 'e', 'd', 'p', 'q', 'exp1', 'exp2', 'coef')
 
@@ -296,7 +296,7 @@
 
     @classmethod
     def _load_pkcs1_der(cls, keyfile):
-        r'''Loads a key in PKCS#1 DER format.
+        r"""Loads a key in PKCS#1 DER format.
 
         @param keyfile: contents of a DER-encoded file that contains the private
             key.
@@ -313,7 +313,7 @@
         >>> PrivateKey._load_pkcs1_der(der)
         PrivateKey(3727264081, 65537, 3349121513, 65063, 57287)
 
-        '''
+        """
 
         from pyasn1.codec.der import decoder
         (priv, _) = decoder.decode(keyfile)
@@ -340,10 +340,10 @@
         return cls(*as_ints)
 
     def _save_pkcs1_der(self):
-        '''Saves the private key in PKCS#1 DER format.
+        """Saves the private key in PKCS#1 DER format.
 
         @returns: the DER-encoded private key.
-        '''
+        """
 
         from pyasn1.type import univ, namedtype
         from pyasn1.codec.der import encoder
@@ -377,7 +377,7 @@
 
     @classmethod
     def _load_pkcs1_pem(cls, keyfile):
-        '''Loads a PKCS#1 PEM-encoded private key file.
+        """Loads a PKCS#1 PEM-encoded private key file.
 
         The contents of the file before the "-----BEGIN RSA PRIVATE KEY-----" and
         after the "-----END RSA PRIVATE KEY-----" lines is ignored.
@@ -385,22 +385,22 @@
         @param keyfile: contents of a PEM-encoded file that contains the private
             key.
         @return: a PrivateKey object
-        '''
+        """
 
         der = rsa.pem.load_pem(keyfile, b('RSA PRIVATE KEY'))
         return cls._load_pkcs1_der(der)
 
     def _save_pkcs1_pem(self):
-        '''Saves a PKCS#1 PEM-encoded private key file.
+        """Saves a PKCS#1 PEM-encoded private key file.
 
         @return: contents of a PEM-encoded file that contains the private key.
-        '''
+        """
 
         der = self._save_pkcs1_der()
         return rsa.pem.save_pem(der, b('RSA PRIVATE KEY'))
 
 def find_p_q(nbits, getprime_func=rsa.prime.getprime, accurate=True):
-    ''''Returns a tuple of two different primes of nbits bits each.
+    """'Returns a tuple of two different primes of nbits bits each.
     
     The resulting p * q has exacty 2 * nbits bits, and the returned p and q
     will not be equal.
@@ -428,7 +428,7 @@
     >>> common.bit_size(p * q) > 240
     True
     
-    '''
+    """
     
     total_bits = nbits * 2
 
@@ -445,11 +445,11 @@
     q = getprime_func(qbits)
 
     def is_acceptable(p, q):
-        '''Returns True iff p and q are acceptable:
+        """Returns True iff p and q are acceptable:
             
             - p and q differ
             - (p * q) has the right nr of bits (when accurate=True)
-        '''
+        """
 
         if p == q:
             return False
diff --git a/rsa/parallel.py b/rsa/parallel.py
index 82042c8..8c03f79 100644
--- a/rsa/parallel.py
+++ b/rsa/parallel.py
@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Functions for parallel computation on multiple cores.
+"""Functions for parallel computation on multiple cores.
 
 Introduced in Python-RSA 3.1.
 
@@ -22,7 +22,7 @@
 
     Requires Python 2.6 or newer.
 
-'''
+"""
 
 import multiprocessing as mp
 
diff --git a/rsa/pem.py b/rsa/pem.py
index 0875ec3..b632ceb 100644
--- a/rsa/pem.py
+++ b/rsa/pem.py
@@ -14,18 +14,18 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Functions that load and write PEM-encoded files.'''
+"""Functions that load and write PEM-encoded files."""
 
 import base64
 from rsa._compat import b, is_bytes
 
 def _markers(pem_marker):
-    '''Returns the start and end PEM markers
+    """Returns the start and end PEM markers
 
     >>> _markers('RSA PRIVATE KEY')
     ('-----BEGIN RSA PRIVATE KEY-----', '-----END RSA PRIVATE KEY-----')
 
-    '''
+    """
 
     if is_bytes(pem_marker):
         pem_marker = pem_marker.decode('utf-8')
@@ -34,7 +34,7 @@
             b('-----END %s-----' % pem_marker))
 
 def load_pem(contents, pem_marker):
-    '''Loads a PEM file.
+    """Loads a PEM file.
 
     @param contents: the contents of the file to interpret
     @param pem_marker: the marker of the PEM content, such as 'RSA PRIVATE KEY'
@@ -46,7 +46,7 @@
     @raise ValueError: when the content is invalid, for example when the start
         marker cannot be found.
 
-    '''
+    """
 
     (pem_start, pem_end) = _markers(pem_marker)
 
@@ -96,7 +96,7 @@
 
 
 def save_pem(contents, pem_marker):
-    '''Saves a PEM file.
+    """Saves a PEM file.
 
     @param contents: the contents to encode in PEM format
     @param pem_marker: the marker of the PEM content, such as 'RSA PRIVATE KEY'
@@ -105,7 +105,7 @@
 
     @return the base64-encoded content between the start and end markers.
 
-    '''
+    """
 
     (pem_start, pem_end) = _markers(pem_marker)
 
diff --git a/rsa/pkcs1.py b/rsa/pkcs1.py
index 8c6d290..4c92111 100644
--- a/rsa/pkcs1.py
+++ b/rsa/pkcs1.py
@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Functions for PKCS#1 version 1.5 encryption and signing
+"""Functions for PKCS#1 version 1.5 encryption and signing
 
 This module implements certain functionality from PKCS#1 version 1.5. For a
 very clear example, read http://www.di-mgt.com.au/rsa_alg.html#pkcs1schemes
@@ -26,7 +26,7 @@
 The exceptions that are raised contain the Python traceback information, which
 can be used to deduce where in the process the failure occurred. DO NOT PASS
 SUCH INFORMATION to your users.
-'''
+"""
 
 import hashlib
 import os
@@ -52,16 +52,16 @@
 }
 
 class CryptoError(Exception):
-    '''Base class for all exceptions in this module.'''
+    """Base class for all exceptions in this module."""
 
 class DecryptionError(CryptoError):
-    '''Raised when decryption fails.'''
+    """Raised when decryption fails."""
 
 class VerificationError(CryptoError):
-    '''Raised when verification fails.'''
+    """Raised when verification fails."""
  
 def _pad_for_encryption(message, target_length):
-    r'''Pads the message for encryption, returning the padded message.
+    r"""Pads the message for encryption, returning the padded message.
     
     :return: 00 02 RANDOM_DATA 00 MESSAGE
     
@@ -73,7 +73,7 @@
     >>> block[-6:]
     '\x00hello'
 
-    '''
+    """
 
     max_msglength = target_length - 11
     msglength = len(message)
@@ -107,7 +107,7 @@
     
 
 def _pad_for_signing(message, target_length):
-    r'''Pads the message for signing, returning the padded message.
+    r"""Pads the message for signing, returning the padded message.
     
     The padding is always a repetition of FF bytes.
     
@@ -123,7 +123,7 @@
     >>> block[2:-6]
     '\xff\xff\xff\xff\xff\xff\xff\xff'
     
-    '''
+    """
 
     max_msglength = target_length - 11
     msglength = len(message)
@@ -141,7 +141,7 @@
     
     
 def encrypt(message, pub_key):
-    '''Encrypts the given message using PKCS#1 v1.5
+    """Encrypts the given message using PKCS#1 v1.5
     
     :param message: the message to encrypt. Must be a byte string no longer than
         ``k-11`` bytes, where ``k`` is the number of bytes needed to encode
@@ -160,7 +160,7 @@
     >>> len(crypto) == common.byte_size(pub_key.n)
     True
     
-    '''
+    """
     
     keylength = common.byte_size(pub_key.n)
     padded = _pad_for_encryption(message, keylength)
@@ -172,7 +172,7 @@
     return block
 
 def decrypt(crypto, priv_key):
-    r'''Decrypts the given message using PKCS#1 v1.5
+    r"""Decrypts the given message using PKCS#1 v1.5
     
     The decryption is considered 'failed' when the resulting cleartext doesn't
     start with the bytes 00 02, or when the 00 byte between the padding and
@@ -220,7 +220,7 @@
     ...
     DecryptionError: Decryption failed
 
-    '''
+    """
     
     blocksize = common.byte_size(priv_key.n)
     encrypted = transform.bytes2int(crypto)
@@ -240,7 +240,7 @@
     return cleartext[sep_idx+1:]
     
 def sign(message, priv_key, hash):
-    '''Signs the message with the private key.
+    """Signs the message with the private key.
 
     Hashes the message, then signs the hash with the given key. This is known
     as a "detached signature", because the message itself isn't altered.
@@ -255,7 +255,7 @@
     :raise OverflowError: if the private key is too small to contain the
         requested hash.
 
-    '''
+    """
 
     # Get the ASN1 code for this hash method
     if hash not in HASH_ASN1:
@@ -277,7 +277,7 @@
     return block
 
 def verify(message, signature, pub_key):
-    '''Verifies that the signature matches the message.
+    """Verifies that the signature matches the message.
     
     The hash method is detected automatically from the signature.
     
@@ -296,7 +296,7 @@
         key. It's only a tiny bit of information, but every bit makes cracking
         the keys easier.
 
-    '''
+    """
     
     blocksize = common.byte_size(pub_key.n)
     encrypted = transform.bytes2int(signature)
@@ -322,7 +322,7 @@
         raise VerificationError('Verification failed')
 
 def _hash(message, method_name):
-    '''Returns the message digest.
+    """Returns the message digest.
     
     :param message: the signed message. Can be an 8-bit string or a file-like
         object. If ``message`` has a ``read()`` method, it is assumed to be a
@@ -330,7 +330,7 @@
     :param method_name: the hash method, must be a key of
         :py:const:`HASH_METHODS`.
     
-    '''
+    """
 
     if method_name not in HASH_METHODS:
         raise ValueError('Invalid hash method: %s' % method_name)
@@ -350,7 +350,7 @@
 
 
 def _find_method_hash(method_hash):
-    '''Finds the hash method and the hash itself.
+    """Finds the hash method and the hash itself.
     
     :param method_hash: ASN1 code for the hash method concatenated with the
         hash itself.
@@ -360,7 +360,7 @@
     
     :raise VerificationFailed: when the hash method cannot be found
 
-    '''
+    """
 
     for (hashname, asn1code) in HASH_ASN1.items():
         if not method_hash.startswith(asn1code):
diff --git a/rsa/prime.py b/rsa/prime.py
index 4dc190c..141d3df 100644
--- a/rsa/prime.py
+++ b/rsa/prime.py
@@ -14,11 +14,11 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Numerical functions related to primes.
+"""Numerical functions related to primes.
 
 Implementation based on the book Algorithm Design by Michael T. Goodrich and
 Roberto Tamassia, 2002.
-'''
+"""
 
 __all__ = [ 'getprime', 'are_relatively_prime']
 
diff --git a/rsa/randnum.py b/rsa/randnum.py
index 275da0f..f6494d8 100644
--- a/rsa/randnum.py
+++ b/rsa/randnum.py
@@ -14,7 +14,7 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Functions for generating random numbers.'''
+"""Functions for generating random numbers."""
 
 # Source inspired by code by Yesudeep Mangalapilly <yesudeep@gmail.com>
 
@@ -24,11 +24,11 @@
 from rsa._compat import byte
 
 def read_random_bits(nbits):
-    '''Reads 'nbits' random bits.
+    """Reads 'nbits' random bits.
 
     If nbits isn't a whole number of bytes, an extra byte will be appended with
     only the lower bits set.
-    '''
+    """
 
     nbytes, rbits = divmod(nbits, 8)
 
diff --git a/rsa/transform.py b/rsa/transform.py
index 7dba2e0..9ba2fe7 100644
--- a/rsa/transform.py
+++ b/rsa/transform.py
@@ -14,10 +14,10 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Data transformation functions.
+"""Data transformation functions.
 
 From bytes to a number, number to bytes, etc.
-'''
+"""
 
 from __future__ import absolute_import
 
@@ -64,22 +64,6 @@
 
     @throws OverflowError when block_size is given and the number takes up more
         bytes than fit into the block.
-
-    >>> _int2bytes(123456789)
-    b'\x07[\xcd\x15'
-    >>> bytes2int(int2bytes(123456789))
-    123456789
-
-    >>> _int2bytes(123456789, 6)
-    b'\x00\x00\x07[\xcd\x15'
-    >>> bytes2int(int2bytes(123456789, 128))
-    123456789
-
-    >>> _int2bytes(123456789, 3)
-    Traceback (most recent call last):
-    ...
-    OverflowError: Needed 4 bytes for number, but block size is 3
-
     """
     # Type checking
     if not is_integer(number):
diff --git a/rsa/util.py b/rsa/util.py
index db6944e..b6df049 100644
--- a/rsa/util.py
+++ b/rsa/util.py
@@ -14,7 +14,9 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
-'''Utility functions.'''
+"""Utility functions."""
+
+from __future__ import with_statement
 
 import sys
 from optparse import OptionParser
@@ -22,7 +24,7 @@
 import rsa.key
 
 def private_to_public():
-    '''Reads a private key and outputs the corresponding public key.'''
+    """Reads a private key and outputs the corresponding public key."""
 
     # Parse the CLI options
     parser = OptionParser(usage='usage: %prog [options]',
diff --git a/rsa/varblock.py b/rsa/varblock.py
index 51e04fc..d5a342b 100644
--- a/rsa/varblock.py
+++ b/rsa/varblock.py
@@ -13,7 +13,7 @@
 #  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.
-'''VARBLOCK file support
+"""VARBLOCK file support
 
 The VARBLOCK file format is as follows, where || denotes byte concatenation:
 
@@ -30,13 +30,13 @@
 This file format is called the VARBLOCK format, in line with the varint format
 used to denote the block sizes.
 
-'''
+"""
 from rsa._compat import byte
 
 VARBLOCK_VERSION = 1
 
 def read_varint(infile):
-    '''Reads a varint from the file.
+    """Reads a varint from the file.
 
     When the first byte to be read indicates EOF, (0, 0) is returned. When an
     EOF occurs when at least one byte has been read, an EOFError exception is
@@ -45,7 +45,7 @@
     @param infile: the file-like object to read from. It should have a read()
         method.
     @returns (varint, length), the read varint and the number of read bytes.
-    '''
+    """
 
     varint = 0
     read_bytes = 0
@@ -67,12 +67,12 @@
             return (varint, read_bytes)
 
 def write_varint(outfile, value):
-    '''Writes a varint to a file.
+    """Writes a varint to a file.
 
     @param outfile: the file-like object to write to. It should have a write()
         method.
     @returns the number of written bytes.
-    '''
+    """
 
     # there is a big difference between 'write the value 0' (this case) and
     # 'there is nothing left to write' (the false-case of the while loop)
@@ -96,12 +96,12 @@
 
 
 def yield_varblocks(infile):
-    '''Generator, yields each block in the input file.
+    """Generator, yields each block in the input file.
     
     @param infile: file to read, is expected to have the VARBLOCK format as
         described in the module's docstring.
     @yields the contents of each block.
-    '''
+    """
 
     # Check the version number
     first_char = infile.read(1)
@@ -130,11 +130,11 @@
         yield block
 
 def yield_fixedblocks(infile, blocksize):
-    '''Generator, yields each block of ``blocksize`` bytes in the input file.
+    """Generator, yields each block of ``blocksize`` bytes in the input file.
 
     :param infile: file to read and separate in blocks.
     :returns: a generator that yields the contents of each block
-    '''
+    """
 
     while True:
         block = infile.read(blocksize)
diff --git a/speed.sh b/speed.sh
index 02aeb25..a57a527 100755
--- a/speed.sh
+++ b/speed.sh
@@ -1,6 +1,9 @@
 #!/bin/sh
 
 echo "int2bytes speed test"
+echo "pypy"
+pypy -mtimeit -s'from rsa.transform import int2bytes; n = 1<<4096' 'int2bytes(n)'
+pypy -mtimeit -s'from rsa.transform import _int2bytes; n = 1<<4096' '_int2bytes(n)'
 echo "python2.5"
 python2.5 -mtimeit -s'from rsa.transform import int2bytes; n = 1<<4096' 'int2bytes(n)'
 python2.5 -mtimeit -s'from rsa.transform import _int2bytes; n = 1<<4096' '_int2bytes(n)'
@@ -13,9 +16,6 @@
 echo "python3.2"
 python3 -mtimeit -s'from rsa.transform import int2bytes; n = 1<<4096' 'int2bytes(n)'
 python3 -mtimeit -s'from rsa.transform import _int2bytes; n = 1<<4096' '_int2bytes(n)'
-echo "pypy"
-pypy -mtimeit -s'from rsa.transform import int2bytes; n = 1<<4096' 'int2bytes(n)'
-pypy -mtimeit -s'from rsa.transform import _int2bytes; n = 1<<4096' '_int2bytes(n)'
 
 echo "bit_size speed test"
 echo "python2.5"
diff --git a/tests/test_bigfile.py b/tests/test_bigfile.py
index 974da8b..9e3a864 100644
--- a/tests/test_bigfile.py
+++ b/tests/test_bigfile.py
@@ -1,4 +1,4 @@
-'''Tests block operations.'''
+"""Tests block operations."""
 from rsa._compat import b
 
 try:
diff --git a/tests/test_common.py b/tests/test_common.py
new file mode 100644
index 0000000..bad24f8
--- /dev/null
+++ b/tests/test_common.py
@@ -0,0 +1,50 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+import unittest2
+import struct
+from rsa._compat import byte, b
+from rsa.common import byte_size, bit_size, _bit_size
+
+
+class Test_byte(unittest2.TestCase):
+    def test_values(self):
+        self.assertEqual(byte(0), b('\x00'))
+        self.assertEqual(byte(255), b('\xff'))
+
+    def test_struct_error_when_out_of_bounds(self):
+        self.assertRaises(struct.error, byte, 256)
+        self.assertRaises(struct.error, byte, -1)
+
+
+class Test_byte_size(unittest2.TestCase):
+    def test_values(self):
+        self.assertEqual(byte_size(1 << 1023), 128)
+        self.assertEqual(byte_size((1 << 1024) - 1), 128)
+        self.assertEqual(byte_size(1 << 1024), 129)
+
+    def test_zero(self):
+        self.assertEqual(byte_size(0), 0)
+
+    def test_bad_type(self):
+        self.assertRaises(TypeError, byte_size, [])
+        self.assertRaises(TypeError, byte_size, ())
+        self.assertRaises(TypeError, byte_size, dict())
+        self.assertRaises(TypeError, byte_size, "")
+        self.assertRaises(TypeError, byte_size, None)
+
+class Test_bit_size(unittest2.TestCase):
+    def test_values(self):
+        self.assertEqual(bit_size(1023), 10)
+        self.assertEqual(bit_size(1024), 11)
+        self.assertEqual(bit_size(1025), 11)
+        self.assertEqual(bit_size(1 << 1024), 1025)
+        self.assertEqual(bit_size((1 << 1024) + 1), 1025)
+        self.assertEqual(bit_size((1 << 1024) - 1), 1024)
+
+        self.assertEqual(_bit_size(1023), 10)
+        self.assertEqual(_bit_size(1024), 11)
+        self.assertEqual(_bit_size(1025), 11)
+        self.assertEqual(_bit_size(1 << 1024), 1025)
+        self.assertEqual(_bit_size((1 << 1024) + 1), 1025)
+        self.assertEqual(_bit_size((1 << 1024) - 1), 1024)
diff --git a/tests/test_integers.py b/tests/test_integers.py
index 0a712aa..c73be2c 100644
--- a/tests/test_integers.py
+++ b/tests/test_integers.py
@@ -1,4 +1,4 @@
-'''Tests integer operations.'''
+"""Tests integer operations."""
 
 import unittest2
 
diff --git a/tests/test_load_save_keys.py b/tests/test_load_save_keys.py
index fc1a1aa..30bbb21 100644
--- a/tests/test_load_save_keys.py
+++ b/tests/test_load_save_keys.py
@@ -1,4 +1,4 @@
-'''Unittest for saving and loading keys.'''
+"""Unittest for saving and loading keys."""
 
 import base64
 import unittest2
@@ -12,7 +12,7 @@
 B64PUB_DER = b('MAwCBQDeKYlRAgMBAAE=')
 PUBLIC_DER = base64.decodestring(B64PUB_DER)
 
-PRIVATE_PEM = b('''
+PRIVATE_PEM = b("""
 -----BEGIN CONFUSING STUFF-----
 Cruft before the key
 
@@ -24,15 +24,15 @@
 
 Stuff after the key
 -----END CONFUSING STUFF-----
-''' % B64PRIV_DER.decode("utf-8"))
+""" % B64PRIV_DER.decode("utf-8"))
 
-CLEAN_PRIVATE_PEM = b('''\
+CLEAN_PRIVATE_PEM = b("""\
 -----BEGIN RSA PRIVATE KEY-----
 %s
 -----END RSA PRIVATE KEY-----
-''' % B64PRIV_DER.decode("utf-8"))
+""" % B64PRIV_DER.decode("utf-8"))
 
-PUBLIC_PEM = b('''
+PUBLIC_PEM = b("""
 -----BEGIN CONFUSING STUFF-----
 Cruft before the key
 
@@ -44,20 +44,20 @@
 
 Stuff after the key
 -----END CONFUSING STUFF-----
-''' % B64PUB_DER.decode("utf-8"))
+""" % B64PUB_DER.decode("utf-8"))
 
-CLEAN_PUBLIC_PEM = b('''\
+CLEAN_PUBLIC_PEM = b("""\
 -----BEGIN RSA PUBLIC KEY-----
 %s
 -----END RSA PUBLIC KEY-----
-''' % B64PUB_DER.decode("utf-8"))
+""" % B64PUB_DER.decode("utf-8"))
 
 
 class DerTest(unittest2.TestCase):
-    '''Test saving and loading DER keys.'''
+    """Test saving and loading DER keys."""
 
     def test_load_private_key(self):
-        '''Test loading private DER keys.'''
+        """Test loading private DER keys."""
 
         key = rsa.key.PrivateKey.load_pkcs1(PRIVATE_DER, 'DER')
         expected = rsa.key.PrivateKey(3727264081, 65537, 3349121513, 65063, 57287)
@@ -65,7 +65,7 @@
         self.assertEqual(expected, key)
 
     def test_save_private_key(self):
-        '''Test saving private DER keys.'''
+        """Test saving private DER keys."""
 
         key = rsa.key.PrivateKey(3727264081, 65537, 3349121513, 65063, 57287)
         der = key.save_pkcs1('DER')
@@ -73,7 +73,7 @@
         self.assertEqual(PRIVATE_DER, der)
 
     def test_load_public_key(self):
-        '''Test loading public DER keys.'''
+        """Test loading public DER keys."""
 
         key = rsa.key.PublicKey.load_pkcs1(PUBLIC_DER, 'DER')
         expected = rsa.key.PublicKey(3727264081, 65537)
@@ -81,7 +81,7 @@
         self.assertEqual(expected, key)
 
     def test_save_public_key(self):
-        '''Test saving public DER keys.'''
+        """Test saving public DER keys."""
 
         key = rsa.key.PublicKey(3727264081, 65537)
         der = key.save_pkcs1('DER')
@@ -89,11 +89,11 @@
         self.assertEqual(PUBLIC_DER, der)
 
 class PemTest(unittest2.TestCase):
-    '''Test saving and loading PEM keys.'''
+    """Test saving and loading PEM keys."""
 
 
     def test_load_private_key(self):
-        '''Test loading private PEM files.'''
+        """Test loading private PEM files."""
 
         key = rsa.key.PrivateKey.load_pkcs1(PRIVATE_PEM, 'PEM')
         expected = rsa.key.PrivateKey(3727264081, 65537, 3349121513, 65063, 57287)
@@ -101,7 +101,7 @@
         self.assertEqual(expected, key)
 
     def test_save_private_key(self):
-        '''Test saving private PEM files.'''
+        """Test saving private PEM files."""
 
         key = rsa.key.PrivateKey(3727264081, 65537, 3349121513, 65063, 57287)
         pem = key.save_pkcs1('PEM')
@@ -109,7 +109,7 @@
         self.assertEqual(CLEAN_PRIVATE_PEM, pem)
 
     def test_load_public_key(self):
-        '''Test loading public PEM files.'''
+        """Test loading public PEM files."""
 
         key = rsa.key.PublicKey.load_pkcs1(PUBLIC_PEM, 'PEM')
         expected = rsa.key.PublicKey(3727264081, 65537)
@@ -117,7 +117,7 @@
         self.assertEqual(expected, key)
 
     def test_save_public_key(self):
-        '''Test saving public PEM files.'''
+        """Test saving public PEM files."""
 
         key = rsa.key.PublicKey(3727264081, 65537)
         pem = key.save_pkcs1('PEM')
diff --git a/tests/test_pkcs1.py b/tests/test_pkcs1.py
index 55098e2..5d2fbad 100644
--- a/tests/test_pkcs1.py
+++ b/tests/test_pkcs1.py
@@ -1,4 +1,4 @@
-'''Tests string operations.'''
+"""Tests string operations."""
 
 import struct
 import unittest2
@@ -40,9 +40,9 @@
                           self.priv)
 
     def test_randomness(self):
-        '''Encrypting the same message twice should result in different
+        """Encrypting the same message twice should result in different
         cryptos.
-        '''
+        """
         
         message = struct.pack('>IIII', 0, 0, 0, 1)
         encrypted1 = pkcs1.encrypt(message, self.pub)
@@ -56,7 +56,7 @@
         (self.pub, self.priv) = rsa.newkeys(512)
 
     def test_sign_verify(self):
-        '''Test happy flow of sign and verify'''
+        """Test happy flow of sign and verify"""
         
         message = b('je moeder')
         print("\tMessage:   %r" % message)
@@ -67,14 +67,14 @@
         pkcs1.verify(message, signature, self.pub)
 
     def test_alter_message(self):
-        '''Altering the message should let the verification fail.'''
+        """Altering the message should let the verification fail."""
         
         signature = pkcs1.sign(b('je moeder'), self.priv, 'SHA-256')
         self.assertRaises(pkcs1.VerificationError, pkcs1.verify,
                           b('mijn moeder'), signature, self.pub)
 
     def test_sign_different_key(self):
-        '''Signing with another key should let the verification fail.'''
+        """Signing with another key should let the verification fail."""
         
         (otherpub, _) = rsa.newkeys(512)
         
@@ -84,7 +84,7 @@
                           message, signature, otherpub)
 
     def test_multiple_signings(self):
-        '''Signing the same message twice should return the same signatures.'''
+        """Signing the same message twice should return the same signatures."""
         
         message = struct.pack('>IIII', 0, 0, 0, 1)
         signature1 = pkcs1.sign(message, self.priv, 'SHA-1')
diff --git a/tests/test_strings.py b/tests/test_strings.py
index 001456d..a2f9483 100644
--- a/tests/test_strings.py
+++ b/tests/test_strings.py
@@ -1,4 +1,4 @@
-'''Tests string operations.'''
+"""Tests string operations."""
 
 from __future__ import absolute_import
 
diff --git a/tests/test_varblock.py b/tests/test_varblock.py
index 24ea50f..d6465ed 100644
--- a/tests/test_varblock.py
+++ b/tests/test_varblock.py
@@ -1,4 +1,4 @@
-'''Tests varblock operations.'''
+"""Tests varblock operations."""
 
 
 try:
diff --git a/tox.ini b/tox.ini
index 9f0ed5e..949bade 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,32 +1,47 @@
 [tox]
 envlist = py25,py26,py27,py32 #,pypy
 
+[pytest]
+addopts = -n4 --cov rsa --cov-report term-missing
+
 [testenv]
-commands=coverage erase
-         coverage run run_tests.py
-         coverage report -m
-         #coverage html -d htmlcov
+commands=py.test []
 
 [testenv:py25]
 deps=pyasn1 >=0.0.13
      coverage >=3.5
      unittest2
+     PyTest
+     pytest-xdist
+     pytest-cov
 
 [testenv:py26]
 deps=pyasn1 >=0.0.13
      coverage >=3.5
      unittest2
+     PyTest
+     pytest-xdist
+     pytest-cov
 
 [testenv:py27]
 deps=pyasn1 >=0.0.13
      coverage >=3.5
      unittest2
+     PyTest
+     pytest-xdist
+     pytest-cov
 
 [testenv:py32]
 deps=coverage >= 3.5
      unittest2py3k
+     PyTest
+     pytest-xdist
+     pytest-cov
 
 [testenv:pypy]
 deps=pyasn1 >=0.0.13
      coverage >= 3.5
      unittest2
+     PyTest
+     pytest-xdist
+     pytest-cov