getting there AES python

python/README.md

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+## Getting Started
+
+To run this python:
+
+1. **Clone the repository** (if applicable):
+   ```
+   git clone <repository-url>
+   cd hello-world-project
+   ```
+
+2. **Install dependencies**:
+   You can install the required dependencies using pip:
+   ```
+   pip install -r requirements.txt
+   ```
+
+3. **Run the application**:
+   Execute the main Python script:
+   ```
+   python src/main.py
+   ```
+
+## Running Tests
+
+To run the unit tests, you can use the following command:
+```
+python -m unittest discover -s tests
+```

python/requirements.txt

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+# This file is intentionally left blank.

python/setup.py

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+from setuptools import setup, find_packages
+
+setup(
+    name='AES-python',
+    version='0.1.0',
+    author='Thomas Faour',
+    author_email='thomas@thumeit.com',
+    description='My own implementation of AES in python - NOT FOR REAL CRYPTOGRTAPHIC USE.',
+    packages=find_packages(where='src'),
+    package_dir={'': 'src'},
+    install_requires=[],
+    classifiers=[
+        'Programming Language :: Python :: 3',
+        'Operating System :: OS Independent',
+    ],
+    python_requires='>=3.10',
+)

python/src/aes.py

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+from src.utility import *
+
+n_rounds = {
+    128: 9,
+    192: 11,
+    256: 13
+}
+class AES():
+    def __init__(self, key: bytes, size: int = 128):
+        """
+        Initializes the AES object with a key and size.
+        Args:
+            key (bytes): The encryption/decryption key (16, 24, or 32 bytes).
+            size (int): The AES key size in bits (128, 192, or 256). Default is 128.
+        Raises:
+            ValueError: If the key length is not valid for the specified size.
+        """
+        if len(key) not in {16, 24, 32}:
+            raise ValueError(f"Key must be 16, 24, or 32 bytes long, but got {len(key)} bytes.")
+        
+        self.size = size
+
+        self.key = self.get_key_schedule(key)
+
+    def encrypt(self, plaintext: bytes) -> bytes:
+        """
+        Encrypts the given plaintext using AES encryption.
+        Args:
+            plaintext (bytes): The plaintext to be encrypted.
+        Returns:
+            bytes: The encrypted ciphertext.
+        """
+        if len(plaintext) != 16:
+            #multi block AES will come later
+            raise ValueError(f"Plaintext must be 16 bytes long, but got {len(plaintext)} bytes.")            
+        state = plaintext
+        r = 0
+        #step one: AddRoundKey
+        state = xor_bytes(state, b''.join(self.key[r:r + 4]))
+        r += 4
+        #step two: N rounds of SubBytes, ShiftRows, MixColumns, AddRoundKey
+        for i in range(n_rounds[self.size]):
+            state = sub_bytes(state)
+            state = shift_rows(state)
+
+    def get_key_schedule(self, key: bytes) -> list:
+        """
+        Generates the key schedule for AES encryption/decryption.
+        Args:
+            key (bytes): The encryption/decryption key (16, 24, or 32 bytes).
+        Returns:
+            list: The key schedule as a list of bytes.
+        """
+        N = self.size // 32
+        K_words = [key[i:i + 4] for i in range(0, len(key), 4)]
+        R = n_rounds[self.size] + 2 #extra key for first and last rounds
+        rcon = get_rcon(R)
+        W = []
+        for i in range(4*R):
+            if i < N:
+                W.append(K_words[i])
+            elif i >= N and i % N == 0:
+                W.append(xor_bytes(
+                        xor_bytes(
+                            W[i - N],
+                            sub_bytes(rot_bytes(W[i-1]))
+                        ),
+                        rcon[i // N -1]
+                    )
+                )
+            elif i >= N and N > 6 and i % N == 4:
+                W.append(xor_bytes(
+                        W[i-N],
+                        sub_bytes(W[i-1])
+                    )
+                )
+            else:
+                W.append(xor_bytes(W[i-N], W[i-1]))
+        return W
+                    
+

python/src/main.py

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+import argparse
+from pathlib import Path
+
+def hello_world():
+    return "Hello, World!"
+
+def main():
+    parser = argparse.ArgumentParser(description='Python AES Encryption/Decryption Tool')
+    
+    # Create mutually exclusive group for encrypt or decrypt
+    mode_group = parser.add_mutually_exclusive_group(required=True)
+    mode_group.add_argument('-e', '--encrypt', action='store_true',
+                           help='Encrypt mode')
+    mode_group.add_argument('-d', '--decrypt', action='store_true',
+                           help='Decrypt mode')
+    parser.add_argument('-k', '--key', type=Path, required=True,
+                        help='Path to encryption/Decryption key (16, 24, or 32 bytes)')
+    parser.add_argument('-s', '--size', type=int, choices=[128, 192, 256], default=128,
+                        help='AES key size in bits (128, 192, or 256). Default is 128.')
+    
+    args = parser.parse_args()
+
+    key = args.key.read_bytes()
+    if len(key) not in {16, 24, 32}:
+        print(f"Error: Key must be 16, 24, or 32 bytes long, but got {len(key)} bytes.", file=sys.stderr)
+        exit()
+
+    aes = AES(key=key, size=args.size)
+    
+    if args.encrypt:
+        print("Mode: Encryption")
+        # TODO: Read from stdin and implement AES encryption
+        
+    elif args.decrypt:
+        print("Mode: Decryption")
+        # TODO: Read from stdin and implement AES decryption
+
+if __name__ == "__main__":
+    print(hello_world())

python/src/utility.py

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+_SBOX = [
+    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
+    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
+    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
+    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
+    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
+    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
+    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
+    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
+    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
+    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
+    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
+    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
+    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
+    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
+    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
+    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
+]
+
+def s_box(byte: int) -> int:
+    """
+    Substitutes a single byte using the AES S-Box.
+    Args:
+        byte (int): An integer value (0-255) representing the byte to be substituted.
+    Returns:
+        int: The substituted byte value from the AES S-Box.
+    Raises:
+        IndexError: If the input byte is not in the range 0-255.
+    """
+    if not (0 <= byte < 256):
+        raise IndexError("Byte must be in the range 0-255")
+
+    return _SBOX[byte]
+
+def shift_rows(state: bytes) -> bytes:
+    """
+    Performs the ShiftRows transformation on the state.
+    Args:
+        state (bytes): The state to be transformed, expected to be 16 bytes long.
+    Returns:
+        bytes: The transformed state after applying ShiftRows.
+    Raises:
+        ValueError: If the input state is not 16 bytes long.
+    """
+    return b''.join([
+        rot_bytes(state[i:i+4], i//4) for i in range(0, 16, 4)
+    ])
+
+_polynomial = [0x02, 0x03, 0x01, 0x01]
+_mix_cols_mat = [
+    _polynomial,
+    rot_bytes(_polynomial, 1),
+    rot_bytes(_polynomial, 2),
+    rot_bytes(_polynomial, 3),
+]
+
+def mix_columns(state: bytes) -> bytes:
+    """
+    Performs the MixColumns transformation on the state.
+    Args:
+        state (bytes): The state to be transformed, expected to be 16 bytes long.
+    Returns:
+        bytes: The transformed state after applying MixColumns.
+    Raises:
+        ValueError: If the input state is not 16 bytes long.
+    """
+    for i in range(4):
+        b = state[i]
+        newb = state[i]          
+
+
+def rot_bytes(word: bytes, n_rots: int = 1) -> bytes:
+    """
+    Rotates a given bytes array by one byte to the left.
+    """
+    return word[n_rots:] + word[:n_rots]
+
+def sub_bytes(word: bytes) -> bytes:
+    """
+    Applies the S-Box substitution to each byte successively.
+    """
+    return bytes(s_box(byte) for byte in word)
+
+def xor_bytes(a: bytes, b: bytes) -> bytes:
+    """
+    XORs two byte arrays of the same length.
+    Args:
+        a (bytes): First byte array.
+        b (bytes): Second byte array.
+    Returns:
+        bytes: Resulting byte array after XOR operation.
+    Raises:
+        ValueError: If the lengths of the two byte arrays are not equal.
+    """
+    if len(a) != len(b):
+        raise ValueError("Byte arrays must be of the same length")
+    
+    return bytes(x ^ y for x, y in zip(a, b))
+
+def get_rcon(n_rounds: int) -> list:
+    """
+    Generates the round constants for AES key schedule.
+    (is a constant, create here for fun!)
+    Returns:
+        list: A list of round constants as bytes.
+    """
+    rc = []
+    for i in range(n_rounds):
+        if (i == 0):
+            rc.append(0x01)
+        elif (i > 0 and rc[i-1] < 128):
+            rc.append(2 * rc[i - 1])
+        elif (i > 0 and rc[i-1] >= 128):
+            rc.append(((2 * rc[i - 1]) ^ 0x11b)%256)
+
+    return [bytes([r, 0, 0, 0]) for r in rc]
+        

python/tests/test_aes.py

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+import unittest
+from src.aes import s_box
+
+class TestAES(unittest.TestCase):
+    def test_sbox_known_values(self):
+        """Test S-box with known AES standard values."""
+        self.assertEqual(s_box(0x00), 0x63)
+        self.assertEqual(s_box(0x01), 0x7c)
+        self.assertEqual(s_box(0x10), 0xca)
+        self.assertEqual(s_box(0x53), 0xed)
+        self.assertEqual(s_box(0xff), 0x16)
+    
+    def test_sbox_invalid_values(self):
+        """Test S-box with invalid input values."""
+        # Test values outside valid range
+        with self.assertRaises(IndexError):
+            s_box(-1)
+        
+        with self.assertRaises(IndexError):
+            s_box(256)
+        
+        with self.assertRaises(IndexError):
+            s_box(1000)
+
+if __name__ == '__main__':
+    unittest.main()

python/tests/test_main.py

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+import unittest
+from src.main import hello_world
+
+class TestHelloWorld(unittest.TestCase):
+    def test_hello_world(self):
+        self.assertEqual(hello_world(), "Hello, World!")
+
+if __name__ == '__main__':
+    unittest.main()