Reformatting with Black

No functional changes.

14 files changed, 434 insertions, 335 deletions

diff --git a/rsa/__init__.py b/rsa/__init__.py
index 4bc164e..8d23986 100644
--- a/rsa/__init__.py
+++ b/rsa/__init__.py
@@ -22,12 +22,21 @@ prevent repetitions, or other common security improvements. Use with care.
 """
 
 from rsa.key import newkeys, PrivateKey, PublicKey
-from rsa.pkcs1 import encrypt, decrypt, sign, verify, DecryptionError, \
-    VerificationError, find_signature_hash,  sign_hash, compute_hash
+from rsa.pkcs1 import (
+    encrypt,
+    decrypt,
+    sign,
+    verify,
+    DecryptionError,
+    VerificationError,
+    find_signature_hash,
+    sign_hash,
+    compute_hash,
+)
 
 __author__ = "Sybren Stuvel, Barry Mead and Yesudeep Mangalapilly"
-__date__ = '2021-02-24'
-__version__ = '4.8-dev0'
+__date__ = "2021-02-24"
+__version__ = "4.8-dev0"
 
 # Do doctest if we're run directly
 if __name__ == "__main__":
@@ -35,6 +44,17 @@ if __name__ == "__main__":
 
     doctest.testmod()
 
-__all__ = ["newkeys", "encrypt", "decrypt", "sign", "verify", 'PublicKey',
-           'PrivateKey', 'DecryptionError', 'VerificationError',
-           'find_signature_hash', 'compute_hash', 'sign_hash']
+__all__ = [
+    "newkeys",
+    "encrypt",
+    "decrypt",
+    "sign",
+    "verify",
+    "PublicKey",
+    "PrivateKey",
+    "DecryptionError",
+    "VerificationError",
+    "find_signature_hash",
+    "compute_hash",
+    "sign_hash",
+]
diff --git a/rsa/asn1.py b/rsa/asn1.py
index 32b1eb4..4cc4dd3 100644
--- a/rsa/asn1.py
+++ b/rsa/asn1.py
@@ -22,18 +22,19 @@ from pyasn1.type import univ, namedtype, tag
 
 class PubKeyHeader(univ.Sequence):
     componentType = namedtype.NamedTypes(
-            namedtype.NamedType('oid', univ.ObjectIdentifier()),
-            namedtype.NamedType('parameters', univ.Null()),
+        namedtype.NamedType("oid", univ.ObjectIdentifier()),
+        namedtype.NamedType("parameters", univ.Null()),
     )
 
 
 class OpenSSLPubKey(univ.Sequence):
     componentType = namedtype.NamedTypes(
-            namedtype.NamedType('header', PubKeyHeader()),
-
-            # This little hack (the implicit tag) allows us to get a Bit String as Octet String
-            namedtype.NamedType('key', univ.OctetString().subtype(
-                    implicitTag=tag.Tag(tagClass=0, tagFormat=0, tagId=3))),
+        namedtype.NamedType("header", PubKeyHeader()),
+        # This little hack (the implicit tag) allows us to get a Bit String as Octet String
+        namedtype.NamedType(
+            "key",
+            univ.OctetString().subtype(implicitTag=tag.Tag(tagClass=0, tagFormat=0, tagId=3)),
+        ),
     )
 
 
@@ -46,6 +47,6 @@ class AsnPubKey(univ.Sequence):
     """
 
     componentType = namedtype.NamedTypes(
-            namedtype.NamedType('modulus', univ.Integer()),
-            namedtype.NamedType('publicExponent', univ.Integer()),
+        namedtype.NamedType("modulus", univ.Integer()),
+        namedtype.NamedType("publicExponent", univ.Integer()),
     )
diff --git a/rsa/cli.py b/rsa/cli.py
index c7a24f4..5a9c797 100644
--- a/rsa/cli.py
+++ b/rsa/cli.py
@@ -34,21 +34,33 @@ def keygen() -> None:
     """Key generator."""
 
     # Parse the CLI options
-    parser = optparse.OptionParser(usage='usage: %prog [options] keysize',
-                                   description='Generates a new RSA keypair of "keysize" bits.')
-
-    parser.add_option('--pubout', type='string',
-                      help='Output filename for the public key. The public key is '
-                           'not saved if this option is not present. You can use '
-                           'pyrsa-priv2pub to create the public key file later.')
-
-    parser.add_option('-o', '--out', type='string',
-                      help='Output filename for the private key. The key is '
-                           'written to stdout if this option is not present.')
-
-    parser.add_option('--form',
-                      help='key format of the private and public keys - default PEM',
-                      choices=('PEM', 'DER'), default='PEM')
+    parser = optparse.OptionParser(
+        usage="usage: %prog [options] keysize",
+        description='Generates a new RSA keypair of "keysize" bits.',
+    )
+
+    parser.add_option(
+        "--pubout",
+        type="string",
+        help="Output filename for the public key. The public key is "
+        "not saved if this option is not present. You can use "
+        "pyrsa-priv2pub to create the public key file later.",
+    )
+
+    parser.add_option(
+        "-o",
+        "--out",
+        type="string",
+        help="Output filename for the private key. The key is "
+        "written to stdout if this option is not present.",
+    )
+
+    parser.add_option(
+        "--form",
+        help="key format of the private and public keys - default PEM",
+        choices=("PEM", "DER"),
+        default="PEM",
+    )
 
     (cli, cli_args) = parser.parse_args(sys.argv[1:])
 
@@ -60,44 +72,45 @@ def keygen() -> None:
         keysize = int(cli_args[0])
     except ValueError as ex:
         parser.print_help()
-        print('Not a valid number: %s' % cli_args[0], file=sys.stderr)
+        print("Not a valid number: %s" % cli_args[0], file=sys.stderr)
         raise SystemExit(1) from ex
 
-    print('Generating %i-bit key' % keysize, file=sys.stderr)
+    print("Generating %i-bit key" % keysize, file=sys.stderr)
     (pub_key, priv_key) = rsa.newkeys(keysize)
 
     # Save public key
     if cli.pubout:
-        print('Writing public key to %s' % cli.pubout, file=sys.stderr)
+        print("Writing public key to %s" % cli.pubout, file=sys.stderr)
         data = pub_key.save_pkcs1(format=cli.form)
-        with open(cli.pubout, 'wb') as outfile:
+        with open(cli.pubout, "wb") as outfile:
             outfile.write(data)
 
     # Save private key
     data = priv_key.save_pkcs1(format=cli.form)
 
     if cli.out:
-        print('Writing private key to %s' % cli.out, file=sys.stderr)
-        with open(cli.out, 'wb') as outfile:
+        print("Writing private key to %s" % cli.out, file=sys.stderr)
+        with open(cli.out, "wb") as outfile:
             outfile.write(data)
     else:
-        print('Writing private key to stdout', file=sys.stderr)
+        print("Writing private key to stdout", file=sys.stderr)
         sys.stdout.buffer.write(data)
 
 
 class CryptoOperation(metaclass=abc.ABCMeta):
     """CLI callable that operates with input, output, and a key."""
 
-    keyname = 'public'  # or 'private'
-    usage = 'usage: %%prog [options] %(keyname)s_key'
-    description = ''
-    operation = 'decrypt'
-    operation_past = 'decrypted'
-    operation_progressive = 'decrypting'
-    input_help = 'Name of the file to %(operation)s. Reads from stdin if ' \
-                 'not specified.'
-    output_help = 'Name of the file to write the %(operation_past)s file ' \
-                  'to. Written to stdout if this option is not present.'
+    keyname = "public"  # or 'private'
+    usage = "usage: %%prog [options] %(keyname)s_key"
+    description = ""
+    operation = "decrypt"
+    operation_past = "decrypted"
+    operation_progressive = "decrypting"
+    input_help = "Name of the file to %(operation)s. Reads from stdin if " "not specified."
+    output_help = (
+        "Name of the file to write the %(operation_past)s file "
+        "to. Written to stdout if this option is not present."
+    )
     expected_cli_args = 1
     has_output = True
 
@@ -109,8 +122,9 @@ class CryptoOperation(metaclass=abc.ABCMeta):
         self.output_help = self.output_help % self.__class__.__dict__
 
     @abc.abstractmethod
-    def perform_operation(self, indata: bytes, key: rsa.key.AbstractKey,
-                          cli_args: Indexable) -> typing.Any:
+    def perform_operation(
+        self, indata: bytes, key: rsa.key.AbstractKey, cli_args: Indexable
+    ) -> typing.Any:
         """Performs the program's operation.
 
         Implement in a subclass.
@@ -141,14 +155,17 @@ class CryptoOperation(metaclass=abc.ABCMeta):
 
         parser = optparse.OptionParser(usage=self.usage, description=self.description)
 
-        parser.add_option('-i', '--input', type='string', help=self.input_help)
+        parser.add_option("-i", "--input", type="string", help=self.input_help)
 
         if self.has_output:
-            parser.add_option('-o', '--output', type='string', help=self.output_help)
+            parser.add_option("-o", "--output", type="string", help=self.output_help)
 
-        parser.add_option('--keyform',
-                          help='Key format of the %s key - default PEM' % self.keyname,
-                          choices=('PEM', 'DER'), default='PEM')
+        parser.add_option(
+            "--keyform",
+            help="Key format of the %s key - default PEM" % self.keyname,
+            choices=("PEM", "DER"),
+            default="PEM",
+        )
 
         (cli, cli_args) = parser.parse_args(sys.argv[1:])
 
@@ -161,8 +178,8 @@ class CryptoOperation(metaclass=abc.ABCMeta):
     def read_key(self, filename: str, keyform: str) -> rsa.key.AbstractKey:
         """Reads a public or private key."""
 
-        print('Reading %s key from %s' % (self.keyname, filename), file=sys.stderr)
-        with open(filename, 'rb') as keyfile:
+        print("Reading %s key from %s" % (self.keyname, filename), file=sys.stderr)
+        with open(filename, "rb") as keyfile:
             keydata = keyfile.read()
 
         return self.key_class.load_pkcs1(keydata, keyform)
@@ -171,37 +188,39 @@ class CryptoOperation(metaclass=abc.ABCMeta):
         """Read the input file"""
 
         if inname:
-            print('Reading input from %s' % inname, file=sys.stderr)
-            with open(inname, 'rb') as infile:
+            print("Reading input from %s" % inname, file=sys.stderr)
+            with open(inname, "rb") as infile:
                 return infile.read()
 
-        print('Reading input from stdin', file=sys.stderr)
+        print("Reading input from stdin", file=sys.stderr)
         return sys.stdin.buffer.read()
 
     def write_outfile(self, outdata: bytes, outname: str) -> None:
         """Write the output file"""
 
         if outname:
-            print('Writing output to %s' % outname, file=sys.stderr)
-            with open(outname, 'wb') as outfile:
+            print("Writing output to %s" % outname, file=sys.stderr)
+            with open(outname, "wb") as outfile:
                 outfile.write(outdata)
         else:
-            print('Writing output to stdout', file=sys.stderr)
+            print("Writing output to stdout", file=sys.stderr)
             sys.stdout.buffer.write(outdata)
 
 
 class EncryptOperation(CryptoOperation):
     """Encrypts a file."""
 
-    keyname = 'public'
-    description = ('Encrypts a file. The file must be shorter than the key '
-                   'length in order to be encrypted.')
-    operation = 'encrypt'
-    operation_past = 'encrypted'
-    operation_progressive = 'encrypting'
-
-    def perform_operation(self, indata: bytes, pub_key: rsa.key.AbstractKey,
-                          cli_args: Indexable = ()) -> bytes:
+    keyname = "public"
+    description = (
+        "Encrypts a file. The file must be shorter than the key " "length in order to be encrypted."
+    )
+    operation = "encrypt"
+    operation_past = "encrypted"
+    operation_progressive = "encrypting"
+
+    def perform_operation(
+        self, indata: bytes, pub_key: rsa.key.AbstractKey, cli_args: Indexable = ()
+    ) -> bytes:
         """Encrypts files."""
         assert isinstance(pub_key, rsa.key.PublicKey)
         return rsa.encrypt(indata, pub_key)
@@ -210,16 +229,19 @@ class EncryptOperation(CryptoOperation):
 class DecryptOperation(CryptoOperation):
     """Decrypts a file."""
 
-    keyname = 'private'
-    description = ('Decrypts a file. The original file must be shorter than '
-                   'the key length in order to have been encrypted.')
-    operation = 'decrypt'
-    operation_past = 'decrypted'
-    operation_progressive = 'decrypting'
+    keyname = "private"
+    description = (
+        "Decrypts a file. The original file must be shorter than "
+        "the key length in order to have been encrypted."
+    )
+    operation = "decrypt"
+    operation_past = "decrypted"
+    operation_progressive = "decrypting"
     key_class = rsa.PrivateKey
 
-    def perform_operation(self, indata: bytes, priv_key: rsa.key.AbstractKey,
-                          cli_args: Indexable = ()) -> bytes:
+    def perform_operation(
+        self, indata: bytes, priv_key: rsa.key.AbstractKey, cli_args: Indexable = ()
+    ) -> bytes:
         """Decrypts files."""
         assert isinstance(priv_key, rsa.key.PrivateKey)
         return rsa.decrypt(indata, priv_key)
@@ -228,28 +250,32 @@ class DecryptOperation(CryptoOperation):
 class SignOperation(CryptoOperation):
     """Signs a file."""
 
-    keyname = 'private'
-    usage = 'usage: %%prog [options] private_key hash_method'
-    description = ('Signs a file, outputs the signature. Choose the hash '
-                   'method from %s' % ', '.join(HASH_METHODS))
-    operation = 'sign'
-    operation_past = 'signature'
-    operation_progressive = 'Signing'
+    keyname = "private"
+    usage = "usage: %%prog [options] private_key hash_method"
+    description = (
+        "Signs a file, outputs the signature. Choose the hash "
+        "method from %s" % ", ".join(HASH_METHODS)
+    )
+    operation = "sign"
+    operation_past = "signature"
+    operation_progressive = "Signing"
     key_class = rsa.PrivateKey
     expected_cli_args = 2
 
-    output_help = ('Name of the file to write the signature to. Written '
-                   'to stdout if this option is not present.')
+    output_help = (
+        "Name of the file to write the signature to. Written "
+        "to stdout if this option is not present."
+    )
 
-    def perform_operation(self, indata: bytes, priv_key: rsa.key.AbstractKey,
-                          cli_args: Indexable) -> bytes:
+    def perform_operation(
+        self, indata: bytes, priv_key: rsa.key.AbstractKey, cli_args: Indexable
+    ) -> bytes:
         """Signs files."""
         assert isinstance(priv_key, rsa.key.PrivateKey)
 
         hash_method = cli_args[1]
         if hash_method not in HASH_METHODS:
-            raise SystemExit('Invalid hash method, choose one of %s' %
-                             ', '.join(HASH_METHODS))
+            raise SystemExit("Invalid hash method, choose one of %s" % ", ".join(HASH_METHODS))
 
         return rsa.sign(indata, priv_key, hash_method)
 
@@ -257,33 +283,36 @@ class SignOperation(CryptoOperation):
 class VerifyOperation(CryptoOperation):
     """Verify a signature."""
 
-    keyname = 'public'
-    usage = 'usage: %%prog [options] public_key signature_file'
-    description = ('Verifies a signature, exits with status 0 upon success, '
-                   'prints an error message and exits with status 1 upon error.')
-    operation = 'verify'
-    operation_past = 'verified'
-    operation_progressive = 'Verifying'
+    keyname = "public"
+    usage = "usage: %%prog [options] public_key signature_file"
+    description = (
+        "Verifies a signature, exits with status 0 upon success, "
+        "prints an error message and exits with status 1 upon error."
+    )
+    operation = "verify"
+    operation_past = "verified"
+    operation_progressive = "Verifying"
     key_class = rsa.PublicKey
     expected_cli_args = 2
     has_output = False
 
-    def perform_operation(self, indata: bytes, pub_key: rsa.key.AbstractKey,
-                          cli_args: Indexable) -> None:
+    def perform_operation(
+        self, indata: bytes, pub_key: rsa.key.AbstractKey, cli_args: Indexable
+    ) -> None:
         """Verifies files."""
         assert isinstance(pub_key, rsa.key.PublicKey)
 
         signature_file = cli_args[1]
 
-        with open(signature_file, 'rb') as sigfile:
+        with open(signature_file, "rb") as sigfile:
             signature = sigfile.read()
 
         try:
             rsa.verify(indata, signature, pub_key)
         except rsa.VerificationError as ex:
-            raise SystemExit('Verification failed.') from ex
+            raise SystemExit("Verification failed.") from ex
 
-        print('Verification OK', file=sys.stderr)
+        print("Verification OK", file=sys.stderr)
 
 
 encrypt = EncryptOperation()
diff --git a/rsa/common.py b/rsa/common.py
index b5a966a..59d5e62 100644
--- a/rsa/common.py
+++ b/rsa/common.py
@@ -18,7 +18,7 @@ import typing
 
 
 class NotRelativePrimeError(ValueError):
-    def __init__(self, a: int, b: int, d: int, msg: str = '') -> None:
+    def __init__(self, a: int, b: int, d: int, msg: str = "") -> None:
         super().__init__(msg or "%d and %d are not relatively prime, divider=%i" % (a, b, d))
         self.a = a
         self.b = b
@@ -50,7 +50,7 @@ def bit_size(num: int) -> int:
     try:
         return num.bit_length()
     except AttributeError as ex:
-        raise TypeError('bit_size(num) only supports integers, not %r' % type(num)) from ex
+        raise TypeError("bit_size(num) only supports integers, not %r" % type(num)) from ex
 
 
 def byte_size(number: int) -> int:
@@ -103,8 +103,7 @@ def ceil_div(num: int, div: int) -> int:
 
 
 def extended_gcd(a: int, b: int) -> typing.Tuple[int, int, int]:
-    """Returns a tuple (r, i, j) such that r = gcd(a, b) = ia + jb
-    """
+    """Returns a tuple (r, i, j) such that r = gcd(a, b) = ia + jb"""
     # r = gcd(a,b) i = multiplicitive inverse of a mod b
     #      or      j = multiplicitive inverse of b mod a
     # Neg return values for i or j are made positive mod b or a respectively
@@ -179,7 +178,7 @@ def crt(a_values: typing.Iterable[int], modulo_values: typing.Iterable[int]) ->
     return x
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     import doctest
 
     doctest.testmod()
diff --git a/rsa/core.py b/rsa/core.py
index 23032e3..84ed3f8 100644
--- a/rsa/core.py
+++ b/rsa/core.py
@@ -23,18 +23,18 @@ def assert_int(var: int, name: str) -> None:
     if isinstance(var, int):
         return
 
-    raise TypeError('%s should be an integer, not %s' % (name, var.__class__))
+    raise TypeError("%s should be an integer, not %s" % (name, var.__class__))
 
 
 def encrypt_int(message: int, ekey: int, n: int) -> int:
     """Encrypts a message using encryption key 'ekey', working modulo n"""
 
-    assert_int(message, 'message')
-    assert_int(ekey, 'ekey')
-    assert_int(n, 'n')
+    assert_int(message, "message")
+    assert_int(ekey, "ekey")
+    assert_int(n, "n")
 
     if message < 0:
-        raise ValueError('Only non-negative numbers are supported')
+        raise ValueError("Only non-negative numbers are supported")
 
     if message > n:
         raise OverflowError("The message %i is too long for n=%i" % (message, n))
@@ -45,9 +45,9 @@ def encrypt_int(message: int, ekey: int, n: int) -> int:
 def decrypt_int(cyphertext: int, dkey: int, n: int) -> int:
     """Decrypts a cypher text using the decryption key 'dkey', working modulo n"""
 
-    assert_int(cyphertext, 'cyphertext')
-    assert_int(dkey, 'dkey')
-    assert_int(n, 'n')
+    assert_int(cyphertext, "cyphertext")
+    assert_int(dkey, "dkey")
+    assert_int(n, "n")
 
     message = pow(cyphertext, dkey, n)
     return message
diff --git a/rsa/key.py b/rsa/key.py
index 620ab5a..63f3f70 100644
--- a/rsa/key.py
+++ b/rsa/key.py
@@ -50,7 +50,7 @@ DEFAULT_EXPONENT = 65537
 class AbstractKey:
     """Abstract superclass for private and public keys."""
 
-    __slots__ = ('n', 'e', 'blindfac', 'blindfac_inverse', 'mutex')
+    __slots__ = ("n", "e", "blindfac", "blindfac_inverse", "mutex")
 
     def __init__(self, n: int, e: int) -> None:
         self.n = n
@@ -64,7 +64,7 @@ class AbstractKey:
         self.mutex = threading.Lock()
 
     @classmethod
-    def _load_pkcs1_pem(cls, keyfile: bytes) -> 'AbstractKey':
+    def _load_pkcs1_pem(cls, keyfile: bytes) -> "AbstractKey":
         """Loads a key in PKCS#1 PEM format, implement in a subclass.
 
         :param keyfile: contents of a PEM-encoded file that contains
@@ -76,7 +76,7 @@ class AbstractKey:
         """
 
     @classmethod
-    def _load_pkcs1_der(cls, keyfile: bytes) -> 'AbstractKey':
+    def _load_pkcs1_der(cls, keyfile: bytes) -> "AbstractKey":
         """Loads a key in PKCS#1 PEM format, implement in a subclass.
 
         :param keyfile: contents of a DER-encoded file that contains
@@ -102,7 +102,7 @@ class AbstractKey:
         """
 
     @classmethod
-    def load_pkcs1(cls, keyfile: bytes, format: str = 'PEM') -> 'AbstractKey':
+    def load_pkcs1(cls, keyfile: bytes, format: str = "PEM") -> "AbstractKey":
         """Loads a key in PKCS#1 DER or PEM format.
 
         :param keyfile: contents of a DER- or PEM-encoded file that contains
@@ -116,27 +116,28 @@ class AbstractKey:
         """
 
         methods = {
-            'PEM': cls._load_pkcs1_pem,
-            'DER': cls._load_pkcs1_der,
+            "PEM": cls._load_pkcs1_pem,
+            "DER": cls._load_pkcs1_der,
         }
 
         method = cls._assert_format_exists(format, methods)
         return method(keyfile)
 
     @staticmethod
-    def _assert_format_exists(file_format: str, methods: typing.Mapping[str, typing.Callable]) \
-            -> typing.Callable:
-        """Checks whether the given file format exists in 'methods'.
-        """
+    def _assert_format_exists(
+        file_format: str, methods: typing.Mapping[str, typing.Callable]
+    ) -> typing.Callable:
+        """Checks whether the given file format exists in 'methods'."""
 
         try:
             return methods[file_format]
         except KeyError as ex:
-            formats = ', '.join(sorted(methods.keys()))
-            raise ValueError('Unsupported format: %r, try one of %s' % (file_format,
-                                                                        formats)) from ex
+            formats = ", ".join(sorted(methods.keys()))
+            raise ValueError(
+                "Unsupported format: %r, try one of %s" % (file_format, formats)
+            ) from ex
 
-    def save_pkcs1(self, format: str = 'PEM') -> bytes:
+    def save_pkcs1(self, format: str = "PEM") -> bytes:
         """Saves the key in PKCS#1 DER or PEM format.
 
         :param format: the format to save; 'PEM' or 'DER'
@@ -146,8 +147,8 @@ class AbstractKey:
         """
 
         methods = {
-            'PEM': self._save_pkcs1_pem,
-            'DER': self._save_pkcs1_der,
+            "PEM": self._save_pkcs1_pem,
+            "DER": self._save_pkcs1_der,
         }
 
         method = self._assert_format_exists(format, methods)
@@ -186,7 +187,7 @@ class AbstractKey:
             blind_r = rsa.randnum.randint(self.n - 1)
             if rsa.prime.are_relatively_prime(self.n, blind_r):
                 return blind_r
-        raise RuntimeError('unable to find blinding factor')
+        raise RuntimeError("unable to find blinding factor")
 
     def _update_blinding_factor(self) -> typing.Tuple[int, int]:
         """Update blinding factors.
@@ -212,6 +213,7 @@ class AbstractKey:
 
             return self.blindfac, self.blindfac_inverse
 
+
 class PublicKey(AbstractKey):
     """Represents a public RSA key.
 
@@ -236,13 +238,13 @@ class PublicKey(AbstractKey):
 
     """
 
-    __slots__ = ('n', 'e')
+    __slots__ = ("n", "e")
 
     def __getitem__(self, key: str) -> int:
         return getattr(self, key)
 
     def __repr__(self) -> str:
-        return 'PublicKey(%i, %i)' % (self.n, self.e)
+        return "PublicKey(%i, %i)" % (self.n, self.e)
 
     def __getstate__(self) -> typing.Tuple[int, int]:
         """Returns the key as tuple for pickling."""
@@ -269,7 +271,7 @@ class PublicKey(AbstractKey):
         return hash((self.n, self.e))
 
     @classmethod
-    def _load_pkcs1_der(cls, keyfile: bytes) -> 'PublicKey':
+    def _load_pkcs1_der(cls, keyfile: bytes) -> "PublicKey":
         """Loads a key in PKCS#1 DER format.
 
         :param keyfile: contents of a DER-encoded file that contains the public
@@ -293,7 +295,7 @@ class PublicKey(AbstractKey):
         from rsa.asn1 import AsnPubKey
 
         (priv, _) = decoder.decode(keyfile, asn1Spec=AsnPubKey())
-        return cls(n=int(priv['modulus']), e=int(priv['publicExponent']))
+        return cls(n=int(priv["modulus"]), e=int(priv["publicExponent"]))
 
     def _save_pkcs1_der(self) -> bytes:
         """Saves the public key in PKCS#1 DER format.
@@ -307,13 +309,13 @@ class PublicKey(AbstractKey):
 
         # Create the ASN object
         asn_key = AsnPubKey()
-        asn_key.setComponentByName('modulus', self.n)
-        asn_key.setComponentByName('publicExponent', self.e)
+        asn_key.setComponentByName("modulus", self.n)
+        asn_key.setComponentByName("publicExponent", self.e)
 
         return encoder.encode(asn_key)
 
     @classmethod
-    def _load_pkcs1_pem(cls, keyfile: bytes) -> 'PublicKey':
+    def _load_pkcs1_pem(cls, keyfile: bytes) -> "PublicKey":
         """Loads a PKCS#1 PEM-encoded public key file.
 
         The contents of the file before the "-----BEGIN RSA PUBLIC KEY-----" and
@@ -324,7 +326,7 @@ class PublicKey(AbstractKey):
         :return: a PublicKey object
         """
 
-        der = rsa.pem.load_pem(keyfile, 'RSA PUBLIC KEY')
+        der = rsa.pem.load_pem(keyfile, "RSA PUBLIC KEY")
         return cls._load_pkcs1_der(der)
 
     def _save_pkcs1_pem(self) -> bytes:
@@ -335,10 +337,10 @@ class PublicKey(AbstractKey):
         """
 
         der = self._save_pkcs1_der()
-        return rsa.pem.save_pem(der, 'RSA PUBLIC KEY')
+        return rsa.pem.save_pem(der, "RSA PUBLIC KEY")
 
     @classmethod
-    def load_pkcs1_openssl_pem(cls, keyfile: bytes) -> 'PublicKey':
+    def load_pkcs1_openssl_pem(cls, keyfile: bytes) -> "PublicKey":
         """Loads a PKCS#1.5 PEM-encoded public key file from OpenSSL.
 
         These files can be recognised in that they start with BEGIN PUBLIC KEY
@@ -353,11 +355,11 @@ class PublicKey(AbstractKey):
         :return: a PublicKey object
         """
 
-        der = rsa.pem.load_pem(keyfile, 'PUBLIC KEY')
+        der = rsa.pem.load_pem(keyfile, "PUBLIC KEY")
         return cls.load_pkcs1_openssl_der(der)
 
     @classmethod
-    def load_pkcs1_openssl_der(cls, keyfile: bytes) -> 'PublicKey':
+    def load_pkcs1_openssl_der(cls, keyfile: bytes) -> "PublicKey":
         """Loads a PKCS#1 DER-encoded public key file from OpenSSL.
 
         :param keyfile: contents of a DER-encoded file that contains the public
@@ -371,10 +373,10 @@ class PublicKey(AbstractKey):
 
         (keyinfo, _) = decoder.decode(keyfile, asn1Spec=OpenSSLPubKey())
 
-        if keyinfo['header']['oid'] != univ.ObjectIdentifier('1.2.840.113549.1.1.1'):
+        if keyinfo["header"]["oid"] != univ.ObjectIdentifier("1.2.840.113549.1.1.1"):
             raise TypeError("This is not a DER-encoded OpenSSL-compatible public key")
 
-        return cls._load_pkcs1_der(keyinfo['key'][1:])
+        return cls._load_pkcs1_der(keyinfo["key"][1:])
 
 
 class PrivateKey(AbstractKey):
@@ -401,7 +403,7 @@ class PrivateKey(AbstractKey):
 
     """
 
-    __slots__ = ('n', 'e', 'd', 'p', 'q', 'exp1', 'exp2', 'coef')
+    __slots__ = ("n", "e", "d", "p", "q", "exp1", "exp2", "coef")
 
     def __init__(self, n: int, e: int, d: int, p: int, q: int) -> None:
         AbstractKey.__init__(self, n, e)
@@ -418,7 +420,13 @@ class PrivateKey(AbstractKey):
         return getattr(self, key)
 
     def __repr__(self) -> str:
-        return 'PrivateKey(%i, %i, %i, %i, %i)' % (self.n, self.e, self.d, self.p, self.q)
+        return "PrivateKey(%i, %i, %i, %i, %i)" % (
+            self.n,
+            self.e,
+            self.d,
+            self.p,
+            self.q,
+        )
 
     def __getstate__(self) -> typing.Tuple[int, int, int, int, int, int, int, int]:
         """Returns the key as tuple for pickling."""
@@ -436,14 +444,16 @@ class PrivateKey(AbstractKey):
         if not isinstance(other, PrivateKey):
             return False
 
-        return (self.n == other.n and
-                self.e == other.e and
-                self.d == other.d and
-                self.p == other.p and
-                self.q == other.q and
-                self.exp1 == other.exp1 and
-                self.exp2 == other.exp2 and
-                self.coef == other.coef)
+        return (
+            self.n == other.n
+            and self.e == other.e
+            and self.d == other.d
+            and self.p == other.p
+            and self.q == other.q
+            and self.exp1 == other.exp1
+            and self.exp2 == other.exp2
+            and self.coef == other.coef
+        )
 
     def __ne__(self, other: typing.Any) -> bool:
         return not (self == other)
@@ -481,7 +491,7 @@ class PrivateKey(AbstractKey):
         return self.unblind(encrypted, blindfac_inverse)
 
     @classmethod
-    def _load_pkcs1_der(cls, keyfile: bytes) -> 'PrivateKey':
+    def _load_pkcs1_der(cls, keyfile: bytes) -> "PrivateKey":
         """Loads a key in PKCS#1 DER format.
 
         :param keyfile: contents of a DER-encoded file that contains the private
@@ -503,6 +513,7 @@ class PrivateKey(AbstractKey):
         """
 
         from pyasn1.codec.der import decoder
+
         (priv, _) = decoder.decode(keyfile)
 
         # ASN.1 contents of DER encoded private key:
@@ -521,7 +532,7 @@ class PrivateKey(AbstractKey):
         # }
 
         if priv[0] != 0:
-            raise ValueError('Unable to read this file, version %s != 0' % priv[0])
+            raise ValueError("Unable to read this file, version %s != 0" % priv[0])
 
         as_ints = map(int, priv[1:6])
         key = cls(*as_ints)
@@ -530,9 +541,9 @@ class PrivateKey(AbstractKey):
 
         if (key.exp1, key.exp2, key.coef) != (exp1, exp2, coef):
             warnings.warn(
-                'You have provided a malformed keyfile. Either the exponents '
-                'or the coefficient are incorrect. Using the correct values '
-                'instead.',
+                "You have provided a malformed keyfile. Either the exponents "
+                "or the coefficient are incorrect. Using the correct values "
+                "instead.",
                 UserWarning,
             )
 
@@ -550,33 +561,33 @@ class PrivateKey(AbstractKey):
 
         class AsnPrivKey(univ.Sequence):
             componentType = namedtype.NamedTypes(
-                namedtype.NamedType('version', univ.Integer()),
-                namedtype.NamedType('modulus', univ.Integer()),
-                namedtype.NamedType('publicExponent', univ.Integer()),
-                namedtype.NamedType('privateExponent', univ.Integer()),
-                namedtype.NamedType('prime1', univ.Integer()),
-                namedtype.NamedType('prime2', univ.Integer()),
-                namedtype.NamedType('exponent1', univ.Integer()),
-                namedtype.NamedType('exponent2', univ.Integer()),
-                namedtype.NamedType('coefficient', univ.Integer()),
+                namedtype.NamedType("version", univ.Integer()),
+                namedtype.NamedType("modulus", univ.Integer()),
+                namedtype.NamedType("publicExponent", univ.Integer()),
+                namedtype.NamedType("privateExponent", univ.Integer()),
+                namedtype.NamedType("prime1", univ.Integer()),
+                namedtype.NamedType("prime2", univ.Integer()),
+                namedtype.NamedType("exponent1", univ.Integer()),
+                namedtype.NamedType("exponent2", univ.Integer()),
+                namedtype.NamedType("coefficient", univ.Integer()),
             )
 
         # Create the ASN object
         asn_key = AsnPrivKey()
-        asn_key.setComponentByName('version', 0)
-        asn_key.setComponentByName('modulus', self.n)
-        asn_key.setComponentByName('publicExponent', self.e)
-        asn_key.setComponentByName('privateExponent', self.d)
-        asn_key.setComponentByName('prime1', self.p)
-        asn_key.setComponentByName('prime2', self.q)
-        asn_key.setComponentByName('exponent1', self.exp1)
-        asn_key.setComponentByName('exponent2', self.exp2)
-        asn_key.setComponentByName('coefficient', self.coef)
+        asn_key.setComponentByName("version", 0)
+        asn_key.setComponentByName("modulus", self.n)
+        asn_key.setComponentByName("publicExponent", self.e)
+        asn_key.setComponentByName("privateExponent", self.d)
+        asn_key.setComponentByName("prime1", self.p)
+        asn_key.setComponentByName("prime2", self.q)
+        asn_key.setComponentByName("exponent1", self.exp1)
+        asn_key.setComponentByName("exponent2", self.exp2)
+        asn_key.setComponentByName("coefficient", self.coef)
 
         return encoder.encode(asn_key)
 
     @classmethod
-    def _load_pkcs1_pem(cls, keyfile: bytes) -> 'PrivateKey':
+    def _load_pkcs1_pem(cls, keyfile: bytes) -> "PrivateKey":
         """Loads a PKCS#1 PEM-encoded private key file.
 
         The contents of the file before the "-----BEGIN RSA PRIVATE KEY-----" and
@@ -588,7 +599,7 @@ class PrivateKey(AbstractKey):
         :return: a PrivateKey object
         """
 
-        der = rsa.pem.load_pem(keyfile, b'RSA PRIVATE KEY')
+        der = rsa.pem.load_pem(keyfile, b"RSA PRIVATE KEY")
         return cls._load_pkcs1_der(der)
 
     def _save_pkcs1_pem(self) -> bytes:
@@ -599,12 +610,14 @@ class PrivateKey(AbstractKey):
         """
 
         der = self._save_pkcs1_der()
-        return rsa.pem.save_pem(der, b'RSA PRIVATE KEY')
+        return rsa.pem.save_pem(der, b"RSA PRIVATE KEY")
 
 
-def find_p_q(nbits: int,
-             getprime_func: typing.Callable[[int], int] = rsa.prime.getprime,
-             accurate: bool = True) -> typing.Tuple[int, int]:
+def find_p_q(
+    nbits: int,
+    getprime_func: typing.Callable[[int], int] = rsa.prime.getprime,
+    accurate: bool = True,
+) -> typing.Tuple[int, int]:
     """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
@@ -644,16 +657,16 @@ def find_p_q(nbits: int,
     qbits = nbits - shift
 
     # Choose the two initial primes
-    log.debug('find_p_q(%i): Finding p', nbits)
+    log.debug("find_p_q(%i): Finding p", nbits)
     p = getprime_func(pbits)
-    log.debug('find_p_q(%i): Finding q', nbits)
+    log.debug("find_p_q(%i): Finding q", nbits)
     q = getprime_func(qbits)
 
     def is_acceptable(p: int, q: int) -> bool:
         """Returns True iff p and q are acceptable:
 
-            - p and q differ
-            - (p * q) has the right nr of bits (when accurate=True)
+        - p and q differ
+        - (p * q) has the right nr of bits (when accurate=True)
         """
 
         if p == q:
@@ -701,13 +714,17 @@ def calculate_keys_custom_exponent(p: int, q: int, exponent: int) -> typing.Tupl
         d = rsa.common.inverse(exponent, phi_n)
     except rsa.common.NotRelativePrimeError as ex:
         raise rsa.common.NotRelativePrimeError(
-            exponent, phi_n, ex.d,
-            msg="e (%d) and phi_n (%d) are not relatively prime (divider=%i)" %
-                (exponent, phi_n, ex.d)) from ex
+            exponent,
+            phi_n,
+            ex.d,
+            msg="e (%d) and phi_n (%d) are not relatively prime (divider=%i)"
+            % (exponent, phi_n, ex.d),
+        ) from ex
 
     if (exponent * d) % phi_n != 1:
-        raise ValueError("e (%d) and d (%d) are not mult. inv. modulo "
-                         "phi_n (%d)" % (exponent, d, phi_n))
+        raise ValueError(
+            "e (%d) and d (%d) are not mult. inv. modulo " "phi_n (%d)" % (exponent, d, phi_n)
+        )
 
     return exponent, d
 
@@ -725,10 +742,12 @@ def calculate_keys(p: int, q: int) -> typing.Tuple[int, int]:
     return calculate_keys_custom_exponent(p, q, DEFAULT_EXPONENT)
 
 
-def gen_keys(nbits: int,
-             getprime_func: typing.Callable[[int], int],
-             accurate: bool = True,
-             exponent: int = DEFAULT_EXPONENT) -> typing.Tuple[int, int, int, int]:
+def gen_keys(
+    nbits: int,
+    getprime_func: typing.Callable[[int], int],
+    accurate: bool = True,
+    exponent: int = DEFAULT_EXPONENT,
+) -> typing.Tuple[int, int, int, int]:
     """Generate RSA keys of nbits bits. Returns (p, q, e, d).
 
     Note: this can take a long time, depending on the key size.
@@ -756,10 +775,12 @@ def gen_keys(nbits: int,
     return p, q, e, d
 
 
-def newkeys(nbits: int,
-            accurate: bool = True,
-            poolsize: int = 1,
-            exponent: int = DEFAULT_EXPONENT) -> typing.Tuple[PublicKey, PrivateKey]:
+def newkeys(
+    nbits: int,
+    accurate: bool = True,
+    poolsize: int = 1,
+    exponent: int = DEFAULT_EXPONENT,
+) -> typing.Tuple[PublicKey, PrivateKey]:
     """Generates public and private keys, and returns them as (pub, priv).
 
     The public key is also known as the 'encryption key', and is a
@@ -786,10 +807,10 @@ def newkeys(nbits: int,
     """
 
     if nbits < 16:
-        raise ValueError('Key too small')
+        raise ValueError("Key too small")
 
     if poolsize < 1:
-        raise ValueError('Pool size (%i) should be >= 1' % poolsize)
+        raise ValueError("Pool size (%i) should be >= 1" % poolsize)
 
     # Determine which getprime function to use
     if poolsize > 1:
@@ -797,6 +818,7 @@ def newkeys(nbits: int,
 
         def getprime_func(nbits: int) -> int:
             return parallel.getprime(nbits, poolsize=poolsize)
+
     else:
         getprime_func = rsa.prime.getprime
 
@@ -806,15 +828,12 @@ def newkeys(nbits: int,
     # Create the key objects
     n = p * q
 
-    return (
-        PublicKey(n, e),
-        PrivateKey(n, e, d, p, q)
-    )
+    return (PublicKey(n, e), PrivateKey(n, e, d, p, q))
 
 
-__all__ = ['PublicKey', 'PrivateKey', 'newkeys']
+__all__ = ["PublicKey", "PrivateKey", "newkeys"]
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     import doctest
 
     try:
@@ -824,8 +843,8 @@ if __name__ == '__main__':
                 break
 
             if (count % 10 == 0 and count) or count == 1:
-                print('%i times' % count)
+                print("%i times" % count)
     except KeyboardInterrupt:
-        print('Aborted')
+        print("Aborted")
     else:
-        print('Doctests done')
+        print("Doctests done")
diff --git a/rsa/parallel.py b/rsa/parallel.py
index f9afedb..5020edb 100644
--- a/rsa/parallel.py
+++ b/rsa/parallel.py
@@ -62,8 +62,7 @@ def getprime(nbits: int, poolsize: int) -> int:
 
     # Create processes
     try:
-        procs = [mp.Process(target=_find_prime, args=(nbits, pipe_send))
-                 for _ in range(poolsize)]
+        procs = [mp.Process(target=_find_prime, args=(nbits, pipe_send)) for _ in range(poolsize)]
         # Start processes
         for p in procs:
             p.start()
@@ -80,10 +79,10 @@ def getprime(nbits: int, poolsize: int) -> int:
     return result
 
 
-__all__ = ['getprime']
+__all__ = ["getprime"]
 
-if __name__ == '__main__':
-    print('Running doctests 1000x or until failure')
+if __name__ == "__main__":
+    print("Running doctests 1000x or until failure")
     import doctest
 
     for count in range(100):
@@ -92,6 +91,6 @@ if __name__ == '__main__':
             break
 
         if count % 10 == 0 and count:
-            print('%i times' % count)
+            print("%i times" % count)
 
-    print('Doctests done')
+    print("Doctests done")
diff --git a/rsa/pem.py b/rsa/pem.py
index 1ffb446..5d26e6e 100644
--- a/rsa/pem.py
+++ b/rsa/pem.py
@@ -27,10 +27,12 @@ def _markers(pem_marker: FlexiText) -> typing.Tuple[bytes, bytes]:
     """
 
     if not isinstance(pem_marker, bytes):
-        pem_marker = pem_marker.encode('ascii')
+        pem_marker = pem_marker.encode("ascii")
 
-    return (b'-----BEGIN ' + pem_marker + b'-----',
-            b'-----END ' + pem_marker + b'-----')
+    return (
+        b"-----BEGIN " + pem_marker + b"-----",
+        b"-----END " + pem_marker + b"-----",
+    )
 
 
 def _pem_lines(contents: bytes, pem_start: bytes, pem_end: bytes) -> typing.Iterator[bytes]:
@@ -65,7 +67,7 @@ def _pem_lines(contents: bytes, pem_start: bytes, pem_end: bytes) -> typing.Iter
             break
 
         # Load fields
-        if b':' in line:
+        if b":" in line:
             continue
 
         yield line
@@ -95,13 +97,13 @@ def load_pem(contents: FlexiText, pem_marker: FlexiText) -> bytes:
 
     # We want bytes, not text. If it's text, it can be converted to ASCII bytes.
     if not isinstance(contents, bytes):
-        contents = contents.encode('ascii')
+        contents = contents.encode("ascii")
 
     (pem_start, pem_end) = _markers(pem_marker)
     pem_lines = [line for line in _pem_lines(contents, pem_start, pem_end)]
 
     # Base64-decode the contents
-    pem = b''.join(pem_lines)
+    pem = b"".join(pem_lines)
     return base64.standard_b64decode(pem)
 
 
@@ -119,14 +121,14 @@ def save_pem(contents: bytes, pem_marker: FlexiText) -> bytes:
 
     (pem_start, pem_end) = _markers(pem_marker)
 
-    b64 = base64.standard_b64encode(contents).replace(b'\n', b'')
+    b64 = base64.standard_b64encode(contents).replace(b"\n", b"")
     pem_lines = [pem_start]
 
     for block_start in range(0, len(b64), 64):
-        block = b64[block_start:block_start + 64]
+        block = b64[block_start : block_start + 64]
         pem_lines.append(block)
 
     pem_lines.append(pem_end)
-    pem_lines.append(b'')
+    pem_lines.append(b"")
 
-    return b'\n'.join(pem_lines)
+    return b"\n".join(pem_lines)
diff --git a/rsa/pkcs1.py b/rsa/pkcs1.py
index 9adad90..5992c7f 100644
--- a/rsa/pkcs1.py
+++ b/rsa/pkcs1.py
@@ -41,37 +41,41 @@ else:
 
 # ASN.1 codes that describe the hash algorithm used.
 HASH_ASN1 = {
-    'MD5': b'\x30\x20\x30\x0c\x06\x08\x2a\x86\x48\x86\xf7\x0d\x02\x05\x05\x00\x04\x10',
-    'SHA-1': b'\x30\x21\x30\x09\x06\x05\x2b\x0e\x03\x02\x1a\x05\x00\x04\x14',
-    'SHA-224': b'\x30\x2d\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x04\x05\x00\x04\x1c',
-    'SHA-256': b'\x30\x31\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x01\x05\x00\x04\x20',
-    'SHA-384': b'\x30\x41\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x02\x05\x00\x04\x30',
-    'SHA-512': b'\x30\x51\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x03\x05\x00\x04\x40',
+    "MD5": b"\x30\x20\x30\x0c\x06\x08\x2a\x86\x48\x86\xf7\x0d\x02\x05\x05\x00\x04\x10",
+    "SHA-1": b"\x30\x21\x30\x09\x06\x05\x2b\x0e\x03\x02\x1a\x05\x00\x04\x14",
+    "SHA-224": b"\x30\x2d\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x04\x05\x00\x04\x1c",
+    "SHA-256": b"\x30\x31\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x01\x05\x00\x04\x20",
+    "SHA-384": b"\x30\x41\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x02\x05\x00\x04\x30",
+    "SHA-512": b"\x30\x51\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x03\x05\x00\x04\x40",
 }
 
 HASH_METHODS: typing.Dict[str, typing.Callable[[], HashType]] = {
-    'MD5': hashlib.md5,
-    'SHA-1': hashlib.sha1,
-    'SHA-224': hashlib.sha224,
-    'SHA-256': hashlib.sha256,
-    'SHA-384': hashlib.sha384,
-    'SHA-512': hashlib.sha512,
+    "MD5": hashlib.md5,
+    "SHA-1": hashlib.sha1,
+    "SHA-224": hashlib.sha224,
+    "SHA-256": hashlib.sha256,
+    "SHA-384": hashlib.sha384,
+    "SHA-512": hashlib.sha512,
 }
 
 
 if sys.version_info >= (3, 6):
     # Python 3.6 introduced SHA3 support.
-    HASH_ASN1.update({
-        'SHA3-256': b'\x30\x31\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x08\x05\x00\x04\x20',
-        'SHA3-384': b'\x30\x41\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x09\x05\x00\x04\x30',
-        'SHA3-512': b'\x30\x51\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x0a\x05\x00\x04\x40',
-    })
-
-    HASH_METHODS.update({
-        'SHA3-256': hashlib.sha3_256,
-        'SHA3-384': hashlib.sha3_384,
-        'SHA3-512': hashlib.sha3_512,
-    })
+    HASH_ASN1.update(
+        {
+            "SHA3-256": b"\x30\x31\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x08\x05\x00\x04\x20",
+            "SHA3-384": b"\x30\x41\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x09\x05\x00\x04\x30",
+            "SHA3-512": b"\x30\x51\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x0a\x05\x00\x04\x40",
+        }
+    )
+
+    HASH_METHODS.update(
+        {
+            "SHA3-256": hashlib.sha3_256,
+            "SHA3-384": hashlib.sha3_384,
+            "SHA3-512": hashlib.sha3_512,
+        }
+    )
 
 
 class CryptoError(Exception):
@@ -105,11 +109,13 @@ def _pad_for_encryption(message: bytes, target_length: int) -> bytes:
     msglength = len(message)
 
     if msglength > max_msglength:
-        raise OverflowError('%i bytes needed for message, but there is only'
-                            ' space for %i' % (msglength, max_msglength))
+        raise OverflowError(
+            "%i bytes needed for message, but there is only"
+            " space for %i" % (msglength, max_msglength)
+        )
 
     # Get random padding
-    padding = b''
+    padding = b""
     padding_length = target_length - msglength - 3
 
     # We remove 0-bytes, so we'll end up with less padding than we've asked for,
@@ -121,15 +127,12 @@ def _pad_for_encryption(message: bytes, target_length: int) -> bytes:
         # after removing the 0-bytes. This increases the chance of getting
         # enough bytes, especially when needed_bytes is small
         new_padding = os.urandom(needed_bytes + 5)
-        new_padding = new_padding.replace(b'\x00', b'')
+        new_padding = new_padding.replace(b"\x00", b"")
         padding = padding + new_padding[:needed_bytes]
 
     assert len(padding) == padding_length
 
-    return b''.join([b'\x00\x02',
-                     padding,
-                     b'\x00',
-                     message])
+    return b"".join([b"\x00\x02", padding, b"\x00", message])
 
 
 def _pad_for_signing(message: bytes, target_length: int) -> bytes:
@@ -155,15 +158,14 @@ def _pad_for_signing(message: bytes, target_length: int) -> bytes:
     msglength = len(message)
 
     if msglength > max_msglength:
-        raise OverflowError('%i bytes needed for message, but there is only'
-                            ' space for %i' % (msglength, max_msglength))
+        raise OverflowError(
+            "%i bytes needed for message, but there is only"
+            " space for %i" % (msglength, max_msglength)
+        )
 
     padding_length = target_length - msglength - 3
 
-    return b''.join([b'\x00\x01',
-                     padding_length * b'\xff',
-                     b'\x00',
-                     message])
+    return b"".join([b"\x00\x01", padding_length * b"\xff", b"\x00", message])
 
 
 def encrypt(message: bytes, pub_key: key.PublicKey) -> bytes:
@@ -259,13 +261,13 @@ def decrypt(crypto: bytes, priv_key: key.PrivateKey) -> bytes:
     # integer). This fixes CVE-2020-13757.
     if len(crypto) > blocksize:
         # This is operating on public information, so doesn't need to be constant-time.
-        raise DecryptionError('Decryption failed')
+        raise DecryptionError("Decryption failed")
 
     # If we can't find the cleartext marker, decryption failed.
-    cleartext_marker_bad = not compare_digest(cleartext[:2], b'\x00\x02')
+    cleartext_marker_bad = not compare_digest(cleartext[:2], b"\x00\x02")
 
     # Find the 00 separator between the padding and the message
-    sep_idx = cleartext.find(b'\x00', 2)
+    sep_idx = cleartext.find(b"\x00", 2)
 
     # sep_idx indicates the position of the `\x00` separator that separates the
     # padding from the actual message. The padding should be at least 8 bytes
@@ -276,9 +278,9 @@ def decrypt(crypto: bytes, priv_key: key.PrivateKey) -> bytes:
 
     anything_bad = cleartext_marker_bad | sep_idx_bad
     if anything_bad:
-        raise DecryptionError('Decryption failed')
+        raise DecryptionError("Decryption failed")
 
-    return cleartext[sep_idx + 1:]
+    return cleartext[sep_idx + 1 :]
 
 
 def sign_hash(hash_value: bytes, priv_key: key.PrivateKey, hash_method: str) -> bytes:
@@ -299,7 +301,7 @@ def sign_hash(hash_value: bytes, priv_key: key.PrivateKey, hash_method: str) ->
 
     # Get the ASN1 code for this hash method
     if hash_method not in HASH_ASN1:
-        raise ValueError('Invalid hash method: %s' % hash_method)
+        raise ValueError("Invalid hash method: %s" % hash_method)
     asn1code = HASH_ASN1[hash_method]
 
     # Encrypt the hash with the private key
@@ -365,11 +367,11 @@ def verify(message: bytes, signature: bytes, pub_key: key.PublicKey) -> str:
     expected = _pad_for_signing(cleartext, keylength)
 
     if len(signature) != keylength:
-        raise VerificationError('Verification failed')
+        raise VerificationError("Verification failed")
 
     # Compare with the signed one
     if expected != clearsig:
-        raise VerificationError('Verification failed')
+        raise VerificationError("Verification failed")
 
     return method_name
 
@@ -426,7 +428,7 @@ def compute_hash(message: typing.Union[bytes, typing.BinaryIO], method_name: str
     """
 
     if method_name not in HASH_METHODS:
-        raise ValueError('Invalid hash method: %s' % method_name)
+        raise ValueError("Invalid hash method: %s" % method_name)
 
     method = HASH_METHODS[method_name]
     hasher = method()
@@ -434,7 +436,7 @@ def compute_hash(message: typing.Union[bytes, typing.BinaryIO], method_name: str
     if isinstance(message, bytes):
         hasher.update(message)
     else:
-        assert hasattr(message, 'read') and hasattr(message.read, '__call__')
+        assert hasattr(message, "read") and hasattr(message.read, "__call__")
         # read as 1K blocks
         for block in yield_fixedblocks(message, 1024):
             hasher.update(block)
@@ -454,14 +456,21 @@ def _find_method_hash(clearsig: bytes) -> str:
         if asn1code in clearsig:
             return hashname
 
-    raise VerificationError('Verification failed')
+    raise VerificationError("Verification failed")
 
 
-__all__ = ['encrypt', 'decrypt', 'sign', 'verify',
-           'DecryptionError', 'VerificationError', 'CryptoError']
+__all__ = [
+    "encrypt",
+    "decrypt",
+    "sign",
+    "verify",
+    "DecryptionError",
+    "VerificationError",
+    "CryptoError",
+]
 
-if __name__ == '__main__':
-    print('Running doctests 1000x or until failure')
+if __name__ == "__main__":
+    print("Running doctests 1000x or until failure")
     import doctest
 
     for count in range(1000):
@@ -470,6 +479,6 @@ if __name__ == '__main__':
             break
 
         if count % 100 == 0 and count:
-            print('%i times' % count)
+            print("%i times" % count)
 
-    print('Doctests done')
+    print("Doctests done")
diff --git a/rsa/pkcs1_v2.py b/rsa/pkcs1_v2.py
index ed616f5..d68b907 100644
--- a/rsa/pkcs1_v2.py
+++ b/rsa/pkcs1_v2.py
@@ -25,7 +25,7 @@ from rsa import (
 )
 
 
-def mgf1(seed: bytes, length: int, hasher: str = 'SHA-1') -> bytes:
+def mgf1(seed: bytes, length: int, hasher: str = "SHA-1") -> bytes:
     """
     MGF1 is a Mask Generation Function based on a hash function.
 
@@ -51,13 +51,13 @@ def mgf1(seed: bytes, length: int, hasher: str = 'SHA-1') -> bytes:
         hash_length = pkcs1.HASH_METHODS[hasher]().digest_size
     except KeyError as ex:
         raise ValueError(
-            'Invalid `hasher` specified. Please select one of: {hash_list}'.format(
-                hash_list=', '.join(sorted(pkcs1.HASH_METHODS.keys()))
+            "Invalid `hasher` specified. Please select one of: {hash_list}".format(
+                hash_list=", ".join(sorted(pkcs1.HASH_METHODS.keys()))
             )
         ) from ex
 
     # If l > 2^32(hLen), output "mask too long" and stop.
-    if length > (2**32 * hash_length):
+    if length > (2 ** 32 * hash_length):
         raise OverflowError(
             "Desired length should be at most 2**32 times the hasher's output "
             "length ({hash_length} for {hasher} function)".format(
@@ -69,7 +69,7 @@ def mgf1(seed: bytes, length: int, hasher: str = 'SHA-1') -> bytes:
     # Looping `counter` from 0 to ceil(l / hLen)-1, build `output` based on the
     # hashes formed by (`seed` + C), being `C` an octet string of length 4
     # generated by converting `counter` with the primitive I2OSP
-    output = b''.join(
+    output = b"".join(
         pkcs1.compute_hash(
             seed + transform.int2bytes(counter, fill_size=4),
             method_name=hasher,
@@ -82,11 +82,11 @@ def mgf1(seed: bytes, length: int, hasher: str = 'SHA-1') -> bytes:
 
 
 __all__ = [
-    'mgf1',
+    "mgf1",
 ]
 
-if __name__ == '__main__':
-    print('Running doctests 1000x or until failure')
+if __name__ == "__main__":
+    print("Running doctests 1000x or until failure")
     import doctest
 
     for count in range(1000):
@@ -95,6 +95,6 @@ if __name__ == '__main__':
             break
 
         if count % 100 == 0 and count:
-            print('%i times' % count)
+            print("%i times" % count)
 
-    print('Doctests done')
+    print("Doctests done")
diff --git a/rsa/prime.py b/rsa/prime.py
index 853aca5..d8980d0 100644
--- a/rsa/prime.py
+++ b/rsa/prime.py
@@ -21,7 +21,7 @@ Roberto Tamassia, 2002.
 import rsa.common
 import rsa.randnum
 
-__all__ = ['getprime', 'are_relatively_prime']
+__all__ = ["getprime", "are_relatively_prime"]
 
 
 def gcd(p: int, q: int) -> int:
@@ -183,8 +183,8 @@ def are_relatively_prime(a: int, b: int) -> bool:
     return d == 1
 
 
-if __name__ == '__main__':
-    print('Running doctests 1000x or until failure')
+if __name__ == "__main__":
+    print("Running doctests 1000x or until failure")
     import doctest
 
     for count in range(1000):
@@ -193,6 +193,6 @@ if __name__ == '__main__':
             break
 
         if count % 100 == 0 and count:
-            print('%i times' % count)
+            print("%i times" % count)
 
-    print('Doctests done')
+    print("Doctests done")
diff --git a/rsa/randnum.py b/rsa/randnum.py
index a5bb850..c65facd 100644
--- a/rsa/randnum.py
+++ b/rsa/randnum.py
@@ -37,15 +37,14 @@ def read_random_bits(nbits: int) -> bytes:
     # Add the remaining random bits
     if rbits > 0:
         randomvalue = ord(os.urandom(1))
-        randomvalue >>= (8 - rbits)
+        randomvalue >>= 8 - rbits
         randomdata = struct.pack("B", randomvalue) + randomdata
 
     return randomdata
 
 
 def read_random_int(nbits: int) -> int:
-    """Reads a random integer of approximately nbits bits.
-    """
+    """Reads a random integer of approximately nbits bits."""
 
     randomdata = read_random_bits(nbits)
     value = transform.bytes2int(randomdata)
diff --git a/rsa/transform.py b/rsa/transform.py
index 03c4a77..c609b65 100644
--- a/rsa/transform.py
+++ b/rsa/transform.py
@@ -31,7 +31,7 @@ def bytes2int(raw_bytes: bytes) -> int:
     8405007
 
     """
-    return int.from_bytes(raw_bytes, 'big', signed=False)
+    return int.from_bytes(raw_bytes, "big", signed=False)
 
 
 def int2bytes(number: int, fill_size: int = 0) -> bytes:
@@ -61,12 +61,12 @@ def int2bytes(number: int, fill_size: int = 0) -> bytes:
     bytes_required = max(1, math.ceil(number.bit_length() / 8))
 
     if fill_size > 0:
-        return number.to_bytes(fill_size, 'big')
+        return number.to_bytes(fill_size, "big")
 
-    return number.to_bytes(bytes_required, 'big')
+    return number.to_bytes(bytes_required, "big")
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     import doctest
 
     doctest.testmod()
diff --git a/rsa/util.py b/rsa/util.py
index cb31c46..087caf8 100644
--- a/rsa/util.py
+++ b/rsa/util.py
@@ -24,36 +24,57 @@ def private_to_public() -> None:
     """Reads a private key and outputs the corresponding public key."""
 
     # Parse the CLI options
-    parser = OptionParser(usage='usage: %prog [options]',
-                          description='Reads a private key and outputs the '
-                                      'corresponding public key. Both private and public keys use '
-                                      'the format described in PKCS#1 v1.5')
+    parser = OptionParser(
+        usage="usage: %prog [options]",
+        description="Reads a private key and outputs the "
+        "corresponding public key. Both private and public keys use "
+        "the format described in PKCS#1 v1.5",
+    )
 
-    parser.add_option('-i', '--input', dest='infilename', type='string',
-                      help='Input filename. Reads from stdin if not specified')
-    parser.add_option('-o', '--output', dest='outfilename', type='string',
-                      help='Output filename. Writes to stdout of not specified')
+    parser.add_option(
+        "-i",
+        "--input",
+        dest="infilename",
+        type="string",
+        help="Input filename. Reads from stdin if not specified",
+    )
+    parser.add_option(
+        "-o",
+        "--output",
+        dest="outfilename",
+        type="string",
+        help="Output filename. Writes to stdout of not specified",
+    )
 
-    parser.add_option('--inform', dest='inform',
-                      help='key format of input - default PEM',
-                      choices=('PEM', 'DER'), default='PEM')
+    parser.add_option(
+        "--inform",
+        dest="inform",
+        help="key format of input - default PEM",
+        choices=("PEM", "DER"),
+        default="PEM",
+    )
 
-    parser.add_option('--outform', dest='outform',
-                      help='key format of output - default PEM',
-                      choices=('PEM', 'DER'), default='PEM')
+    parser.add_option(
+        "--outform",
+        dest="outform",
+        help="key format of output - default PEM",
+        choices=("PEM", "DER"),
+        default="PEM",
+    )
 
     (cli, cli_args) = parser.parse_args(sys.argv)
 
     # Read the input data
     if cli.infilename:
-        print('Reading private key from %s in %s format' %
-              (cli.infilename, cli.inform), file=sys.stderr)
-        with open(cli.infilename, 'rb') as infile:
+        print(
+            "Reading private key from %s in %s format" % (cli.infilename, cli.inform),
+            file=sys.stderr,
+        )
+        with open(cli.infilename, "rb") as infile:
             in_data = infile.read()
     else:
-        print('Reading private key from stdin in %s format' % cli.inform,
-              file=sys.stderr)
-        in_data = sys.stdin.read().encode('ascii')
+        print("Reading private key from stdin in %s format" % cli.inform, file=sys.stderr)
+        in_data = sys.stdin.read().encode("ascii")
 
     assert type(in_data) == bytes, type(in_data)
 
@@ -65,11 +86,12 @@ def private_to_public() -> None:
     out_data = pub_key.save_pkcs1(cli.outform)
 
     if cli.outfilename:
-        print('Writing public key to %s in %s format' %
-              (cli.outfilename, cli.outform), file=sys.stderr)
-        with open(cli.outfilename, 'wb') as outfile:
+        print(
+            "Writing public key to %s in %s format" % (cli.outfilename, cli.outform),
+            file=sys.stderr,
+        )
+        with open(cli.outfilename, "wb") as outfile:
             outfile.write(out_data)
     else:
-        print('Writing public key to stdout in %s format' % cli.outform,
-              file=sys.stderr)
-        sys.stdout.write(out_data.decode('ascii'))
+        print("Writing public key to stdout in %s format" % cli.outform, file=sys.stderr)
+        sys.stdout.write(out_data.decode("ascii"))