Improve documentation

README.rst

@@ -23,6 +23,7 @@ This driver depends on:
 
 * `Adafruit CircuitPython <https://github.com/adafruit/circuitpython>`_
 * `Adafruit CircuitPython Logger Module <https://github.com/adafruit/Adafruit_CircuitPython_Logger>`_
+* `pyasn1 Module <https://github.com/etingof/pyasn1>`_
 
 Please ensure all dependencies are available on the CircuitPython filesystem.
 This is easily achieved by downloading

adafruit_rsa/__init__.py

@@ -3,12 +3,14 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-"""RSA module
+"""
+RSA module
+====================================================
 
 Module for calculating large primes, and RSA encryption, decryption, signing
 and verification. Includes generating public and private keys.
 
-WARNING: this implementation does not use compression of the cleartext input to
+**WARNING:** This implementation does not use compression of the cleartext input to
 prevent repetitions, or other common security improvements. Use with care.
 
 """

adafruit_rsa/_compat.py

@@ -3,11 +3,21 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-"""Python compatibility wrappers."""
+"""
+`adafruit_rsa._compat`
+====================================================
+
+Python compatibility wrappers.
+"""
 
 import sys
 from struct import pack
 
+try:
+    from typing import Any, Literal, Tuple
+except ImportError:
+    pass
+
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_RSA.git"
 
@@ -31,87 +41,86 @@
 INTEGER_TYPES = (int,)
 
 
-def write_to_stdout(data):
+def write_to_stdout(data: bytes) -> None:
     """Writes bytes to stdout
 
-    :type data: bytes
+    :param bytes data: Data to write
     """
     # On Py3 we must use the buffer interface to write bytes.
     sys.stdout.buffer.write(data)
 
 
-def is_bytes(obj):
+def is_bytes(obj: Any) -> bool:
     """
     Determines whether the given value is a byte string.
 
     :param obj:
         The value to test.
-    :returns:
-        ``True`` if ``value`` is a byte string; ``False`` otherwise.
+    :return:
+        ``True`` if ``obj`` is a byte string; ``False`` otherwise.
     """
     return isinstance(obj, bytes)
 
 
-def is_integer(obj):
+def is_integer(obj: Any) -> bool:
     """
     Determines whether the given value is an integer.
 
     :param obj:
         The value to test.
-    :returns:
-        ``True`` if ``value`` is an integer; ``False`` otherwise.
+    :return:
+        ``True`` if ``obj`` is an integer; ``False`` otherwise.
     """
     return isinstance(obj, INTEGER_TYPES)
 
 
-def byte(num):
+def byte(num: int) -> bytes:
     """
     Converts a number between 0 and 255 (both inclusive) to a base-256 (byte)
     representation.
 
     Use it as a replacement for ``chr`` where you are expecting a byte
     because this will work on all current versions of Python::
 
-    :param num:
-        An unsigned integer between 0 and 255 (both inclusive).
-    :returns:
-        A single byte.
+    :param int num: An unsigned integer between 0 and 255 (both inclusive).
+    :return: A single byte.
     """
     return pack("B", num)
 
 
-def xor_bytes(bytes_1, bytes_2):
+def xor_bytes(bytes_1: bytes, bytes_2: bytes) -> bytes:
     """
     Returns the bitwise XOR result between two bytes objects, bytes_1 ^ bytes_2.
 
     Bitwise XOR operation is commutative, so order of parameters doesn't
     generate different results. If parameters have different length, extra
     length of the largest one is ignored.
 
-    :param bytes_1:
-        First bytes object.
-    :param bytes_2:
-        Second bytes object.
-    :returns:
-        Bytes object, result of XOR operation.
+    :param bytes bytes_1: First bytes object.
+    :param bytes_2: Second bytes object.
+    :return: Bytes object, result of XOR operation.
     """
     return bytes(x ^ y for x, y in zip(bytes_1, bytes_2))
 
 
-def get_word_alignment(num, force_arch=64, _machine_word_size=MACHINE_WORD_SIZE):
+def get_word_alignment(
+    num: int,
+    force_arch: int = 64,
+    _machine_word_size: Literal[64, 32] = MACHINE_WORD_SIZE,
+) -> Tuple[int, int, int, str]:
     """
     Returns alignment details for the given number based on the platform
     Python is running on.
 
-    :param num:
-        Unsigned integral number.
-    :param force_arch:
+    :param int num:
+        Unsigned integer number.
+    :param int force_arch:
         If you don't want to use 64-bit unsigned chunks, set this to
         anything other than 64. 32-bit chunks will be preferred then.
         Default 64 will be used when on a 64-bit machine.
-    :param _machine_word_size:
+    :param int _machine_word_size:
         (Internal) The machine word size used for alignment.
-    :returns:
+    :return:
         4-tuple::
 
             (word_bits, word_bytes,

adafruit_rsa/asn1.py

@@ -3,7 +3,11 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-"""ASN.1 definitions.
+"""
+`adafruit_rsa.asn1`
+====================================================
+
+ASN.1 definitions.
 
 Not all ASN.1-handling code use these definitions, but when it does, they should be here.
 """

adafruit_rsa/common.py

@@ -3,17 +3,31 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-"""Common functionality shared by several modules."""
+"""
+`adafruit_rsa.common`
+====================================================
+
+Common functionality shared by several modules.
+"""
 
 # pylint: disable=invalid-name
 
+try:
+    from typing import Optional, Tuple, Sequence
+except ImportError:
+    pass
+
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_RSA.git"
 
 
-def bit_length(int_type):
+def bit_length(int_type: int) -> int:
     """Return the number of bits necessary to represent an integer in binary,
-    excluding the sign and leading zeros"""
+    excluding the sign and leading zeros
+
+    :param int int_type: The integer to check
+    """
+
     length = 0
     while int_type:
         int_type >>= 1
@@ -24,7 +38,7 @@ def bit_length(int_type):
 class NotRelativePrimeError(ValueError):
     """Raises if provided a and b not relatively prime."""
 
-    def __init__(self, a, b, d, msg=None):
+    def __init__(self, a: int, b: int, d: int, msg: Optional[str] = None):
         super().__init__(
             msg or "%d and %d are not relatively prime, divider=%i" % (a, b, d)
         )
@@ -33,7 +47,7 @@ def __init__(self, a, b, d, msg=None):
         self.d = d
 
 
-def bit_size(num):
+def bit_size(num: int) -> int:
     """
     Number of bits needed to represent a integer excluding any prefix
     0 bits.
@@ -47,11 +61,11 @@ def bit_size(num):
         >>> bit_size(1025)
         11
 
-    :param num:
+    :param int num:
         Integer value. If num is 0, returns 0. Only the absolute value of the
         number is considered. Therefore, signed integers will be abs(num)
         before the number's bit length is determined.
-    :returns:
+    :return:
         Returns the number of bits in the integer.
     """
 
@@ -63,7 +77,7 @@ def bit_size(num):
         ) from err
 
 
-def byte_size(number):
+def byte_size(number: int) -> int:
     """
     Returns the number of bytes required to hold a specific long number.
 
@@ -78,21 +92,19 @@ def byte_size(number):
         >>> byte_size(1 << 1024)
         129
 
-    :param number:
-        An unsigned integer
-    :returns:
-        The number of bytes required to hold a specific long number.
+    :param int number: An unsigned integer
+    :return: The number of bytes required to hold a specific long number.
     """
     if number == 0:
         return 1
     return ceil_div(bit_size(number), 8)
 
 
-def ceil_div(num, div):
+def ceil_div(num: int, div: int) -> int:
     """
-    Returns the ceiling function of a division between `num` and `div`.
+    Returns the ceiling function of a division between ``num`` and ``div``.
 
-    Usage::
+    Usage:
 
         >>> ceil_div(100, 7)
         15
@@ -101,9 +113,8 @@ def ceil_div(num, div):
         >>> ceil_div(1, 4)
         1
 
-    :param num: Division's numerator, a number
-    :param div: Division's divisor, a number
-
+    :param int num: Division's numerator, a number
+    :param int div: Division's divisor, a number
     :return: Rounded up result of the division between the parameters.
     """
     quanta, mod = divmod(num, div)
@@ -112,7 +123,7 @@ def ceil_div(num, div):
     return quanta
 
 
-def extended_gcd(a, b):
+def extended_gcd(a: int, b: int) -> Tuple[int, int, int]:
     """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
@@ -136,7 +147,7 @@ def extended_gcd(a, b):
     return a, lx, ly  # Return only positive values
 
 
-def inverse(x, n):
+def inverse(x: int, n: int) -> int:
     """Returns the inverse of x % n under multiplication, a.k.a x^-1 (mod n)
 
     >>> inverse(7, 4)
@@ -153,14 +164,14 @@ def inverse(x, n):
     return inv
 
 
-def crt(a_values, modulo_values):
+def crt(a_values: Sequence[int], modulo_values: Sequence[int]) -> int:
     """Chinese Remainder Theorem.
 
     Calculates x such that x = a[i] (mod m[i]) for each i.
 
-    :param a_values: the a-values of the above equation
-    :param modulo_values: the m-values of the above equation
-    :returns: x such that x = a[i] (mod m[i]) for each i
+    :param Sequence[int] a_values: the a-values of the above equation
+    :param Sequence[int] modulo_values: the m-values of the above equation
+    :return: x such that x = a[i] (mod m[i]) for each i
 
 
     >>> crt([2, 3], [3, 5])

adafruit_rsa/core.py

@@ -3,7 +3,11 @@
 #
 # SPDX-License-Identifier: Apache-2.0
 
-"""Core mathematical operations.
+"""
+`adafruit_rsa.core`
+====================================================
+
+Core mathematical operations.
 
 This is the actual core RSA implementation, which is only defined
 mathematically on integers.
@@ -12,12 +16,18 @@
 # pylint: disable=invalid-name
 from adafruit_rsa._compat import is_integer
 
+try:
+    from typing import Any
+except ImportError:
+    pass
+
 __version__ = "0.0.0-auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_RSA.git"
 
 
-def fast_pow(x, e, m):
+def fast_pow(x: int, e: int, m: int) -> int:
     """Performs fast modular exponentiation, saves RAM on small CPUs/micros.
+
     :param int x: Base
     :param int y: Exponent
     :param int e: Second exponent
@@ -35,15 +45,15 @@ def fast_pow(x, e, m):
     return Y
 
 
-def assert_int(var, name):
+def assert_int(var: Any, name: str) -> None:
     """Asserts provided variable is an integer."""
     if is_integer(var):
         return
 
     raise TypeError("%s should be an integer, not %s" % (name, var.__class__))
 
 
-def encrypt_int(message, ekey, n):
+def encrypt_int(message: int, ekey: int, n: int) -> int:
     """Encrypts a message using encryption key 'ekey', working modulo n"""
 
     assert_int(message, "message")
@@ -61,7 +71,7 @@ def encrypt_int(message, ekey, n):
     return fast_pow(message, ekey, n)
 
 
-def decrypt_int(cyphertext, dkey, n):
+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")